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llvm/llvm-project/6b26457a0ef2994de54606eb5c356cb897cadda2/./llvm/lib/Target/ARM/ARMFrameLowering.cpp
blob: b70abf55dc67e755ba3d42c00be0d1faee667548 [file]
//===- ARMFrameLowering.cpp - ARM Frame Information -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the ARM implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
//
// This file contains the ARM implementation of TargetFrameLowering class.
//
// On ARM, stack frames are structured as follows:
//
// The stack grows downward.
//
// All of the individual frame areas on the frame below are optional, i.e. it's
// possible to create a function so that the particular area isn't present
// in the frame.
//
// At function entry, the "frame" looks as follows:
//
// | | Higher address
// |-----------------------------------|
// | |
// | arguments passed on the stack |
// | |
// |-----------------------------------| <- sp
// | | Lower address
//
//
// After the prologue has run, the frame has the following general structure.
// Technically the last frame area (VLAs) doesn't get created until in the
// main function body, after the prologue is run. However, it's depicted here
// for completeness.
//
// | | Higher address
// |-----------------------------------|
// | |
// | arguments passed on the stack |
// | |
// |-----------------------------------| <- (sp at function entry)
// | |
// | varargs from registers |
// | |
// |-----------------------------------|
// | |
// | prev_lr |
// | prev_fp |
// | (a.k.a. "frame record") |
// | |
// |- - - - - - - - - - - - - - - - - -| <- fp (r7 or r11)
// | |
// | callee-saved gpr registers |
// | |
// |-----------------------------------|
// | |
// | callee-saved fp/simd regs |
// | |
// |-----------------------------------|
// |.empty.space.to.make.part.below....|
// |.aligned.in.case.it.needs.more.than| (size of this area is unknown at
// |.the.standard.8-byte.alignment.....| compile time; if present)
// |-----------------------------------|
// | |
// | local variables of fixed size |
// | including spill slots |
// |-----------------------------------| <- base pointer (not defined by ABI,
// |.variable-sized.local.variables....| LLVM chooses r6)
// |.(VLAs)............................| (size of this area is unknown at
// |...................................| compile time)
// |-----------------------------------| <- sp
// | | Lower address
//
//
// To access the data in a frame, at-compile time, a constant offset must be
// computable from one of the pointers (fp, bp, sp) to access it. The size
// of the areas with a dotted background cannot be computed at compile-time
// if they are present, making it required to have all three of fp, bp and
// sp to be set up to be able to access all contents in the frame areas,
// assuming all of the frame areas are non-empty.
//
// For most functions, some of the frame areas are empty. For those functions,
// it may not be necessary to set up fp or bp:
// * A base pointer is definitely needed when there are both VLAs and local
// variables with more-than-default alignment requirements.
// * A frame pointer is definitely needed when there are local variables with
// more-than-default alignment requirements.
//
// In some cases when a base pointer is not strictly needed, it is generated
// anyway when offsets from the frame pointer to access local variables become
// so large that the offset can't be encoded in the immediate fields of loads
// or stores.
//
// The frame pointer might be chosen to be r7 or r11, depending on the target
// architecture and operating system. See ARMSubtarget::getFramePointerReg for
// details.
//
// Outgoing function arguments must be at the bottom of the stack frame when
// calling another function. If we do not have variable-sized stack objects, we
// can allocate a "reserved call frame" area at the bottom of the local
// variable area, large enough for all outgoing calls. If we do have VLAs, then
// the stack pointer must be decremented and incremented around each call to
// make space for the arguments below the VLAs.
//
//===----------------------------------------------------------------------===//
#include "ARMFrameLowering.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
#include "ARMConstantPoolValue.h"
#include "ARMMachineFunctionInfo.h"
#include "ARMSubtarget.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "MCTargetDesc/ARMBaseInfo.h"
#include "Utils/ARMBaseInfo.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/CFIInstBuilder.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <utility>
#include <vector>
#define DEBUG_TYPE "arm-frame-lowering"
using namespace llvm;
static cl::opt<bool>
SpillAlignedNEONRegs("align-neon-spills", cl::Hidden, cl::init(true),
cl::desc("Align ARM NEON spills in prolog and epilog"));
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs);
enum class SpillArea {
GPRCS1,
GPRCS2,
FPStatus,
DPRCS1,
DPRCS2,
GPRCS3,
FPCXT,
};
/// Get the spill area that Reg should be saved into in the prologue.
SpillArea getSpillArea(Register Reg,
ARMSubtarget::PushPopSplitVariation Variation,
unsigned NumAlignedDPRCS2Regs,
const ARMBaseRegisterInfo *RegInfo) {
// NoSplit:
// push {r0-r12, lr} GPRCS1
// vpush {r8-d15} DPRCS1
//
// SplitR7:
// push {r0-r7, lr} GPRCS1
// push {r8-r12} GPRCS2
// vpush {r8-d15} DPRCS1
//
// SplitR11WindowsSEH:
// push {r0-r10, r12} GPRCS1
// vpush {r8-d15} DPRCS1
// push {r11, lr} GPRCS3
//
// SplitR11AAPCSSignRA:
// push {r0-r10, r12} GPRSC1
// push {r11, lr} GPRCS2
// vpush {r8-d15} DPRCS1
// If FPCXTNS is spilled (for CMSE secure entryfunctions), it is always at
// the top of the stack frame.
// The DPRCS2 region is used for ABIs which only guarantee 4-byte alignment
// of SP. If used, it will be below the other save areas, after the stack has
// been re-aligned.
switch (Reg) {
default:
dbgs() << "Don't know where to spill " << printReg(Reg, RegInfo) << "\n";
llvm_unreachable("Don't know where to spill this register");
break;
case ARM::FPCXTNS:
return SpillArea::FPCXT;
case ARM::FPSCR:
case ARM::FPEXC:
return SpillArea::FPStatus;
case ARM::R0:
case ARM::R1:
case ARM::R2:
case ARM::R3:
case ARM::R4:
case ARM::R5:
case ARM::R6:
case ARM::R7:
return SpillArea::GPRCS1;
case ARM::R8:
case ARM::R9:
case ARM::R10:
if (Variation == ARMSubtarget::SplitR7)
return SpillArea::GPRCS2;
else
return SpillArea::GPRCS1;
case ARM::R11:
if (Variation == ARMSubtarget::SplitR7 ||
Variation == ARMSubtarget::SplitR11AAPCSSignRA)
return SpillArea::GPRCS2;
if (Variation == ARMSubtarget::SplitR11WindowsSEH)
return SpillArea::GPRCS3;
return SpillArea::GPRCS1;
case ARM::R12:
if (Variation == ARMSubtarget::SplitR7)
return SpillArea::GPRCS2;
else
return SpillArea::GPRCS1;
case ARM::LR:
if (Variation == ARMSubtarget::SplitR11AAPCSSignRA)
return SpillArea::GPRCS2;
if (Variation == ARMSubtarget::SplitR11WindowsSEH)
return SpillArea::GPRCS3;
return SpillArea::GPRCS1;
case ARM::D0:
case ARM::D1:
case ARM::D2:
case ARM::D3:
case ARM::D4:
case ARM::D5:
case ARM::D6:
case ARM::D7:
return SpillArea::DPRCS1;
case ARM::D8:
case ARM::D9:
case ARM::D10:
case ARM::D11:
case ARM::D12:
case ARM::D13:
case ARM::D14:
case ARM::D15:
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
return SpillArea::DPRCS2;
else
return SpillArea::DPRCS1;
case ARM::D16:
case ARM::D17:
case ARM::D18:
case ARM::D19:
case ARM::D20:
case ARM::D21:
case ARM::D22:
case ARM::D23:
case ARM::D24:
case ARM::D25:
case ARM::D26:
case ARM::D27:
case ARM::D28:
case ARM::D29:
case ARM::D30:
case ARM::D31:
return SpillArea::DPRCS1;
}
}
ARMFrameLowering::ARMFrameLowering(const ARMSubtarget &sti)
: TargetFrameLowering(StackGrowsDown, sti.getStackAlignment(), 0, Align(4)),
STI(sti) {}
bool ARMFrameLowering::keepFramePointer(const MachineFunction &MF) const {
// iOS always has a FP for backtracking, force other targets to keep their FP
// when doing FastISel. The emitted code is currently superior, and in cases
// like test-suite's lencod FastISel isn't quite correct when FP is eliminated.
return MF.getSubtarget<ARMSubtarget>().useFastISel();
}
/// Returns true if the target can safely skip saving callee-saved registers
/// for noreturn nounwind functions.
bool ARMFrameLowering::enableCalleeSaveSkip(const MachineFunction &MF) const {
assert(MF.getFunction().hasFnAttribute(Attribute::NoReturn) &&
MF.getFunction().hasFnAttribute(Attribute::NoUnwind) &&
!MF.getFunction().hasFnAttribute(Attribute::UWTable));
// Frame pointer and link register are not treated as normal CSR, thus we
// can always skip CSR saves for nonreturning functions.
return true;
}
/// hasFPImpl - Return true if the specified function should have a dedicated
/// frame pointer register. This is true if the function has variable sized
/// allocas or if frame pointer elimination is disabled.
bool ARMFrameLowering::hasFPImpl(const MachineFunction &MF) const {
const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
const MachineFrameInfo &MFI = MF.getFrameInfo();
// Check to see if the target want to forcibly keep frame pointer.
if (keepFramePointer(MF))
return true;
// ABI-required frame pointer.
if (MF.disableFramePointerElim())
return true;
// Frame pointer required for use within this function.
return (RegInfo->hasStackRealignment(MF) || MFI.hasVarSizedObjects() ||
MFI.isFrameAddressTaken());
}
/// isFPReserved - Return true if the frame pointer register should be
/// considered a reserved register on the scope of the specified function.
bool ARMFrameLowering::isFPReserved(const MachineFunction &MF) const {
return hasFP(MF) || MF.framePointerIsReserved();
}
/// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
/// not required, we reserve argument space for call sites in the function
/// immediately on entry to the current function. This eliminates the need for
/// add/sub sp brackets around call sites. Returns true if the call frame is
/// included as part of the stack frame.
bool ARMFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
unsigned CFSize = MFI.getMaxCallFrameSize();
// It's not always a good idea to include the call frame as part of the
// stack frame. ARM (especially Thumb) has small immediate offset to
// address the stack frame. So a large call frame can cause poor codegen
// and may even makes it impossible to scavenge a register.
if (CFSize >= ((1 << 12) - 1) / 2) // Half of imm12
return false;
return !MFI.hasVarSizedObjects();
}
/// canSimplifyCallFramePseudos - If there is a reserved call frame, the
/// call frame pseudos can be simplified. Unlike most targets, having a FP
/// is not sufficient here since we still may reference some objects via SP
/// even when FP is available in Thumb2 mode.
bool
ARMFrameLowering::canSimplifyCallFramePseudos(const MachineFunction &MF) const {
return hasReservedCallFrame(MF) || MF.getFrameInfo().hasVarSizedObjects();
}
// Returns how much of the incoming argument stack area we should clean up in an
// epilogue. For the C calling convention this will be 0, for guaranteed tail
// call conventions it can be positive (a normal return or a tail call to a
// function that uses less stack space for arguments) or negative (for a tail
// call to a function that needs more stack space than us for arguments).
static int getArgumentStackToRestore(MachineFunction &MF,
MachineBasicBlock &MBB) {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
bool IsTailCallReturn = false;
if (MBB.end() != MBBI) {
unsigned RetOpcode = MBBI->getOpcode();
IsTailCallReturn = RetOpcode == ARM::TCRETURNdi ||
RetOpcode == ARM::TCRETURNri ||
RetOpcode == ARM::TCRETURNrinotr12;
}
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int ArgumentPopSize = 0;
if (IsTailCallReturn) {
MachineOperand &StackAdjust = MBBI->getOperand(1);
// For a tail-call in a callee-pops-arguments environment, some or all of
// the stack may actually be in use for the call's arguments, this is
// calculated during LowerCall and consumed here...
ArgumentPopSize = StackAdjust.getImm();
} else {
// ... otherwise the amount to pop is *all* of the argument space,
// conveniently stored in the MachineFunctionInfo by
// LowerFormalArguments. This will, of course, be zero for the C calling
// convention.
ArgumentPopSize = AFI->getArgumentStackToRestore();
}
return ArgumentPopSize;
}
static bool needsWinCFI(const MachineFunction &MF) {
const Function &F = MF.getFunction();
return MF.getTarget().getMCAsmInfo().usesWindowsCFI() &&
F.needsUnwindTableEntry();
}
// Given a load or a store instruction, generate an appropriate unwinding SEH
// code on Windows.
static MachineBasicBlock::iterator insertSEH(MachineBasicBlock::iterator MBBI,
const TargetInstrInfo &TII,
unsigned Flags) {
unsigned Opc = MBBI->getOpcode();
MachineBasicBlock *MBB = MBBI->getParent();
MachineFunction &MF = *MBB->getParent();
DebugLoc DL = MBBI->getDebugLoc();
MachineInstrBuilder MIB;
const ARMSubtarget &Subtarget = MF.getSubtarget<ARMSubtarget>();
const ARMBaseRegisterInfo *RegInfo = Subtarget.getRegisterInfo();
Flags |= MachineInstr::NoMerge;
switch (Opc) {
default:
report_fatal_error("No SEH Opcode for instruction " + TII.getName(Opc));
break;
case ARM::t2ADDri: // add.w r11, sp, #xx
case ARM::t2ADDri12: // add.w r11, sp, #xx
case ARM::t2MOVTi16: // movt r4, #xx
case ARM::tBL: // bl __chkstk
// These are harmless if used for just setting up a frame pointer,
// but that frame pointer can't be relied upon for unwinding, unless
// set up with SEH_SaveSP.
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_Nop))
.addImm(/*Wide=*/1)
.setMIFlags(Flags);
break;
case ARM::t2MOVi16: { // mov(w) r4, #xx
bool Wide = MBBI->getOperand(1).getImm() >= 256;
if (!Wide) {
MachineInstrBuilder NewInstr =
BuildMI(MF, DL, TII.get(ARM::tMOVi8)).setMIFlags(MBBI->getFlags());
NewInstr.add(MBBI->getOperand(0));
NewInstr.add(t1CondCodeOp(/*isDead=*/true));
for (MachineOperand &MO : llvm::drop_begin(MBBI->operands()))
NewInstr.add(MO);
MachineBasicBlock::iterator NewMBBI = MBB->insertAfter(MBBI, NewInstr);
MBB->erase(MBBI);
MBBI = NewMBBI;
}
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_Nop)).addImm(Wide).setMIFlags(Flags);
break;
}
case ARM::tBLXr: // blx r12 (__chkstk)
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_Nop))
.addImm(/*Wide=*/0)
.setMIFlags(Flags);
break;
case ARM::t2MOVi32imm: // movw+movt
// This pseudo instruction expands into two mov instructions. If the
// second operand is a symbol reference, this will stay as two wide
// instructions, movw+movt. If they're immediates, the first one can
// end up as a narrow mov though.
// As two SEH instructions are appended here, they won't get interleaved
// between the two final movw/movt instructions, but it doesn't make any
// practical difference.
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_Nop))
.addImm(/*Wide=*/1)
.setMIFlags(Flags);
MBB->insertAfter(MBBI, MIB);
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_Nop))
.addImm(/*Wide=*/1)
.setMIFlags(Flags);
break;
case ARM::t2STR_PRE:
if (MBBI->getOperand(0).getReg() == ARM::SP &&
MBBI->getOperand(2).getReg() == ARM::SP &&
MBBI->getOperand(3).getImm() == -4) {
unsigned Reg = RegInfo->getSEHRegNum(MBBI->getOperand(1).getReg());
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_SaveRegs))
.addImm(1ULL << Reg)
.addImm(/*Wide=*/1)
.setMIFlags(Flags);
} else {
report_fatal_error("No matching SEH Opcode for t2STR_PRE");
}
break;
case ARM::t2LDR_POST:
if (MBBI->getOperand(1).getReg() == ARM::SP &&
MBBI->getOperand(2).getReg() == ARM::SP &&
MBBI->getOperand(3).getImm() == 4) {
unsigned Reg = RegInfo->getSEHRegNum(MBBI->getOperand(0).getReg());
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_SaveRegs))
.addImm(1ULL << Reg)
.addImm(/*Wide=*/1)
.setMIFlags(Flags);
} else {
report_fatal_error("No matching SEH Opcode for t2LDR_POST");
}
break;
case ARM::t2LDMIA_RET:
case ARM::t2LDMIA_UPD:
case ARM::t2STMDB_UPD: {
unsigned Mask = 0;
bool Wide = false;
for (unsigned i = 4, NumOps = MBBI->getNumOperands(); i != NumOps; ++i) {
const MachineOperand &MO = MBBI->getOperand(i);
if (!MO.isReg() || MO.isImplicit())
continue;
unsigned Reg = RegInfo->getSEHRegNum(MO.getReg());
if (Reg == 15)
Reg = 14;
if (Reg >= 8 && Reg <= 13)
Wide = true;
else if (Opc == ARM::t2LDMIA_UPD && Reg == 14)
Wide = true;
Mask |= 1 << Reg;
}
if (!Wide) {
unsigned NewOpc;
switch (Opc) {
case ARM::t2LDMIA_RET:
NewOpc = ARM::tPOP_RET;
break;
case ARM::t2LDMIA_UPD:
NewOpc = ARM::tPOP;
break;
case ARM::t2STMDB_UPD:
NewOpc = ARM::tPUSH;
break;
default:
llvm_unreachable("");
}
MachineInstrBuilder NewInstr =
BuildMI(MF, DL, TII.get(NewOpc)).setMIFlags(MBBI->getFlags());
for (unsigned i = 2, NumOps = MBBI->getNumOperands(); i != NumOps; ++i)
NewInstr.add(MBBI->getOperand(i));
MachineBasicBlock::iterator NewMBBI = MBB->insertAfter(MBBI, NewInstr);
MBB->erase(MBBI);
MBBI = NewMBBI;
}
unsigned SEHOpc =
(Opc == ARM::t2LDMIA_RET) ? ARM::SEH_SaveRegs_Ret : ARM::SEH_SaveRegs;
MIB = BuildMI(MF, DL, TII.get(SEHOpc))
.addImm(Mask)
.addImm(Wide ? 1 : 0)
.setMIFlags(Flags);
break;
}
case ARM::VSTMDDB_UPD:
case ARM::VLDMDIA_UPD: {
int First = -1, Last = 0;
for (const MachineOperand &MO : llvm::drop_begin(MBBI->operands(), 4)) {
unsigned Reg = RegInfo->getSEHRegNum(MO.getReg());
if (First == -1)
First = Reg;
Last = Reg;
}
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_SaveFRegs))
.addImm(First)
.addImm(Last)
.setMIFlags(Flags);
break;
}
case ARM::tSUBspi:
case ARM::tADDspi:
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_StackAlloc))
.addImm(MBBI->getOperand(2).getImm() * 4)
.addImm(/*Wide=*/0)
.setMIFlags(Flags);
break;
case ARM::t2SUBspImm:
case ARM::t2SUBspImm12:
case ARM::t2ADDspImm:
case ARM::t2ADDspImm12:
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_StackAlloc))
.addImm(MBBI->getOperand(2).getImm())
.addImm(/*Wide=*/1)
.setMIFlags(Flags);
break;
case ARM::tMOVr:
if (MBBI->getOperand(1).getReg() == ARM::SP &&
(Flags & MachineInstr::FrameSetup)) {
unsigned Reg = RegInfo->getSEHRegNum(MBBI->getOperand(0).getReg());
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_SaveSP))
.addImm(Reg)
.setMIFlags(Flags);
} else if (MBBI->getOperand(0).getReg() == ARM::SP &&
(Flags & MachineInstr::FrameDestroy)) {
unsigned Reg = RegInfo->getSEHRegNum(MBBI->getOperand(1).getReg());
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_SaveSP))
.addImm(Reg)
.setMIFlags(Flags);
} else {
report_fatal_error("No SEH Opcode for MOV");
}
break;
case ARM::tBX_RET:
case ARM::t2BXAUT_RET:
case ARM::CLEANUPRET:
case ARM::CATCHRET:
case ARM::TCRETURNri:
case ARM::TCRETURNrinotr12:
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_Nop_Ret))
.addImm(/*Wide=*/0)
.setMIFlags(Flags);
break;
case ARM::TCRETURNdi:
MIB = BuildMI(MF, DL, TII.get(ARM::SEH_Nop_Ret))
.addImm(/*Wide=*/1)
.setMIFlags(Flags);
break;
}
return MBB->insertAfter(MBBI, MIB);
}
static MachineBasicBlock::iterator
initMBBRange(MachineBasicBlock &MBB, const MachineBasicBlock::iterator &MBBI) {
if (MBBI == MBB.begin())
return MachineBasicBlock::iterator();
return std::prev(MBBI);
}
static void insertSEHRange(MachineBasicBlock &MBB,
MachineBasicBlock::iterator Start,
const MachineBasicBlock::iterator &End,
const ARMBaseInstrInfo &TII, unsigned MIFlags) {
if (Start.isValid())
Start = std::next(Start);
else
Start = MBB.begin();
for (auto MI = Start; MI != End;) {
auto Next = std::next(MI);
// Check if this instruction already has got a SEH opcode added. In that
// case, don't do this generic mapping.
if (Next != End && isSEHInstruction(*Next)) {
MI = std::next(Next);
while (MI != End && isSEHInstruction(*MI))
++MI;
continue;
}
insertSEH(MI, TII, MIFlags);
MI = Next;
}
}
static void emitRegPlusImmediate(
bool isARM, MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
const DebugLoc &dl, const ARMBaseInstrInfo &TII, unsigned DestReg,
unsigned SrcReg, int NumBytes, unsigned MIFlags = MachineInstr::NoFlags,
ARMCC::CondCodes Pred = ARMCC::AL, unsigned PredReg = 0) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes,
Pred, PredReg, TII, MIFlags);
else
emitT2RegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes,
Pred, PredReg, TII, MIFlags);
}
static void emitSPUpdate(bool isARM, MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI, const DebugLoc &dl,
const ARMBaseInstrInfo &TII, int NumBytes,
unsigned MIFlags = MachineInstr::NoFlags,
ARMCC::CondCodes Pred = ARMCC::AL,
unsigned PredReg = 0) {
emitRegPlusImmediate(isARM, MBB, MBBI, dl, TII, ARM::SP, ARM::SP, NumBytes,
MIFlags, Pred, PredReg);
}
static int sizeOfSPAdjustment(const MachineInstr &MI) {
int RegSize;
switch (MI.getOpcode()) {
case ARM::VSTMDDB_UPD:
RegSize = 8;
break;
case ARM::STMDB_UPD:
case ARM::t2STMDB_UPD:
RegSize = 4;
break;
case ARM::t2STR_PRE:
case ARM::STR_PRE_IMM:
return 4;
default:
llvm_unreachable("Unknown push or pop like instruction");
}
int count = 0;
// ARM and Thumb2 push/pop insts have explicit "sp, sp" operands (+
// pred) so the list starts at 4.
for (int i = MI.getNumOperands() - 1; i >= 4; --i)
count += RegSize;
return count;
}
static bool WindowsRequiresStackProbe(const MachineFunction &MF,
size_t StackSizeInBytes) {
const MachineFrameInfo &MFI = MF.getFrameInfo();
const Function &F = MF.getFunction();
unsigned StackProbeSize = (MFI.getStackProtectorIndex() > 0) ? 4080 : 4096;
StackProbeSize =
F.getFnAttributeAsParsedInteger("stack-probe-size", StackProbeSize);
return (StackSizeInBytes >= StackProbeSize) &&
!F.hasFnAttribute("no-stack-arg-probe");
}
namespace {
struct StackAdjustingInsts {
struct InstInfo {
MachineBasicBlock::iterator I;
unsigned SPAdjust;
bool BeforeFPSet;
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void dump() {
dbgs() << " " << (BeforeFPSet ? "before-fp " : " ")
<< "sp-adjust=" << SPAdjust;
I->dump();
}
#endif
};
SmallVector<InstInfo, 4> Insts;
void addInst(MachineBasicBlock::iterator I, unsigned SPAdjust,
bool BeforeFPSet = false) {
InstInfo Info = {I, SPAdjust, BeforeFPSet};
Insts.push_back(Info);
}
void addExtraBytes(const MachineBasicBlock::iterator I, unsigned ExtraBytes) {
auto Info =
llvm::find_if(Insts, [&](InstInfo &Info) { return Info.I == I; });
assert(Info != Insts.end() && "invalid sp adjusting instruction");
Info->SPAdjust += ExtraBytes;
}
void emitDefCFAOffsets(MachineBasicBlock &MBB, bool HasFP) {
CFIInstBuilder CFIBuilder(MBB, MBB.end(), MachineInstr::FrameSetup);
unsigned CFAOffset = 0;
for (auto &Info : Insts) {
if (HasFP && !Info.BeforeFPSet)
return;
CFAOffset += Info.SPAdjust;
CFIBuilder.setInsertPoint(std::next(Info.I));
CFIBuilder.buildDefCFAOffset(CFAOffset);
}
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void dump() {
dbgs() << "StackAdjustingInsts:\n";
for (auto &Info : Insts)
Info.dump();
}
#endif
};
} // end anonymous namespace
/// Emit an instruction sequence that will align the address in
/// register Reg by zero-ing out the lower bits. For versions of the
/// architecture that support Neon, this must be done in a single
/// instruction, since skipAlignedDPRCS2Spills assumes it is done in a
/// single instruction. That function only gets called when optimizing
/// spilling of D registers on a core with the Neon instruction set
/// present.
static void emitAligningInstructions(MachineFunction &MF, ARMFunctionInfo *AFI,
const TargetInstrInfo &TII,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, const unsigned Reg,
const Align Alignment,
const bool MustBeSingleInstruction) {
const ARMSubtarget &AST = MF.getSubtarget<ARMSubtarget>();
const bool CanUseBFC = AST.hasV6T2Ops() || AST.hasV7Ops();
const unsigned AlignMask = Alignment.value() - 1U;
const unsigned NrBitsToZero = Log2(Alignment);
assert(!AFI->isThumb1OnlyFunction() && "Thumb1 not supported");
if (!AFI->isThumbFunction()) {
// if the BFC instruction is available, use that to zero the lower
// bits:
// bfc Reg, #0, log2(Alignment)
// otherwise use BIC, if the mask to zero the required number of bits
// can be encoded in the bic immediate field
// bic Reg, Reg, Alignment-1
// otherwise, emit
// lsr Reg, Reg, log2(Alignment)
// lsl Reg, Reg, log2(Alignment)
if (CanUseBFC) {
BuildMI(MBB, MBBI, DL, TII.get(ARM::BFC), Reg)
.addReg(Reg, RegState::Kill)
.addImm(~AlignMask)
.add(predOps(ARMCC::AL));
} else if (AlignMask <= 255) {
BuildMI(MBB, MBBI, DL, TII.get(ARM::BICri), Reg)
.addReg(Reg, RegState::Kill)
.addImm(AlignMask)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
} else {
assert(!MustBeSingleInstruction &&
"Shouldn't call emitAligningInstructions demanding a single "
"instruction to be emitted for large stack alignment for a target "
"without BFC.");
BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg)
.addReg(Reg, RegState::Kill)
.addImm(ARM_AM::getSORegOpc(ARM_AM::lsr, NrBitsToZero))
.add(predOps(ARMCC::AL))
.add(condCodeOp());
BuildMI(MBB, MBBI, DL, TII.get(ARM::MOVsi), Reg)
.addReg(Reg, RegState::Kill)
.addImm(ARM_AM::getSORegOpc(ARM_AM::lsl, NrBitsToZero))
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
} else {
// Since this is only reached for Thumb-2 targets, the BFC instruction
// should always be available.
assert(CanUseBFC);
BuildMI(MBB, MBBI, DL, TII.get(ARM::t2BFC), Reg)
.addReg(Reg, RegState::Kill)
.addImm(~AlignMask)
.add(predOps(ARMCC::AL));
}
}
/// We need the offset of the frame pointer relative to other MachineFrameInfo
/// offsets which are encoded relative to SP at function begin.
/// See also emitPrologue() for how the FP is set up.
/// Unfortunately we cannot determine this value in determineCalleeSaves() yet
/// as assignCalleeSavedSpillSlots() hasn't run at this point. Instead we use
/// this to produce a conservative estimate that we check in an assert() later.
static int getMaxFPOffset(const ARMSubtarget &STI, const ARMFunctionInfo &AFI,
const MachineFunction &MF) {
ARMSubtarget::PushPopSplitVariation PushPopSplit =
STI.getPushPopSplitVariation(MF);
// For Thumb1, push.w isn't available, so the first push will always push
// r7 and lr onto the stack first.
if (AFI.isThumb1OnlyFunction())
return -AFI.getArgRegsSaveSize() - (2 * 4);
// This is a conservative estimation: Assume the frame pointer being r7 and
// pc("r15") up to r8 getting spilled before (= 8 registers).
int MaxRegBytes = 8 * 4;
if (PushPopSplit == ARMSubtarget::SplitR11AAPCSSignRA)
// Here, r11 can be stored below all of r4-r15.
MaxRegBytes = 11 * 4;
if (PushPopSplit == ARMSubtarget::SplitR11WindowsSEH) {
// Here, r11 can be stored below all of r4-r15 plus d8-d15.
MaxRegBytes = 11 * 4 + 8 * 8;
}
int FPCXTSaveSize =
(STI.hasV8_1MMainlineOps() && AFI.isCmseNSEntryFunction()) ? 4 : 0;
return -FPCXTSaveSize - AFI.getArgRegsSaveSize() - MaxRegBytes;
}
void ARMFrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo &MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const TargetMachine &TM = MF.getTarget();
const ARMBaseRegisterInfo *RegInfo = STI.getRegisterInfo();
const ARMBaseInstrInfo &TII = *STI.getInstrInfo();
assert(!AFI->isThumb1OnlyFunction() &&
"This emitPrologue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
Align Alignment = STI.getFrameLowering()->getStackAlign();
unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize();
unsigned NumBytes = MFI.getStackSize();
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
int FPCXTSaveSize = 0;
bool NeedsWinCFI = needsWinCFI(MF);
ARMSubtarget::PushPopSplitVariation PushPopSplit =
STI.getPushPopSplitVariation(MF);
LLVM_DEBUG(dbgs() << "Emitting prologue for " << MF.getName() << "\n");
// Debug location must be unknown since the first debug location is used
// to determine the end of the prologue.
DebugLoc dl;
Register FramePtr = RegInfo->getFrameRegister(MF);
// Determine the sizes of each callee-save spill areas and record which frame
// belongs to which callee-save spill areas.
unsigned GPRCS1Size = 0, GPRCS2Size = 0, FPStatusSize = 0,
DPRCS1Size = 0, GPRCS3Size = 0, DPRCS2Size = 0;
int FramePtrSpillFI = 0;
int D8SpillFI = 0;
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction().getCallingConv() == CallingConv::GHC)
return;
StackAdjustingInsts DefCFAOffsetCandidates;
bool HasFP = hasFP(MF);
if (!AFI->hasStackFrame() &&
(!STI.isTargetWindows() || !WindowsRequiresStackProbe(MF, NumBytes))) {
if (NumBytes != 0) {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
DefCFAOffsetCandidates.addInst(std::prev(MBBI), NumBytes, true);
}
if (!NeedsWinCFI)
DefCFAOffsetCandidates.emitDefCFAOffsets(MBB, HasFP);
if (NeedsWinCFI && MBBI != MBB.begin()) {
insertSEHRange(MBB, {}, MBBI, TII, MachineInstr::FrameSetup);
BuildMI(MBB, MBBI, dl, TII.get(ARM::SEH_PrologEnd))
.setMIFlag(MachineInstr::FrameSetup);
MF.setHasWinCFI(true);
}
return;
}
// Determine spill area sizes, and some important frame indices.
SpillArea FramePtrSpillArea = SpillArea::GPRCS1;
bool BeforeFPPush = true;
for (const CalleeSavedInfo &I : CSI) {
MCRegister Reg = I.getReg();
int FI = I.getFrameIdx();
SpillArea Area = getSpillArea(Reg, PushPopSplit,
AFI->getNumAlignedDPRCS2Regs(), RegInfo);
if (Reg == FramePtr.asMCReg()) {
FramePtrSpillFI = FI;
FramePtrSpillArea = Area;
}
if (Reg == ARM::D8)
D8SpillFI = FI;
switch (Area) {
case SpillArea::FPCXT:
FPCXTSaveSize += 4;
break;
case SpillArea::GPRCS1:
GPRCS1Size += 4;
break;
case SpillArea::GPRCS2:
GPRCS2Size += 4;
break;
case SpillArea::FPStatus:
FPStatusSize += 4;
break;
case SpillArea::DPRCS1:
DPRCS1Size += 8;
break;
case SpillArea::GPRCS3:
GPRCS3Size += 4;
break;
case SpillArea::DPRCS2:
DPRCS2Size += 8;
break;
}
}
MachineBasicBlock::iterator LastPush = MBB.end(), GPRCS1Push, GPRCS2Push,
DPRCS1Push, GPRCS3Push;
// Move past the PAC computation.
if (AFI->shouldSignReturnAddress())
LastPush = MBBI++;
// Move past FPCXT area.
if (FPCXTSaveSize > 0) {
LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, FPCXTSaveSize, BeforeFPPush);
}
// Allocate the vararg register save area.
if (ArgRegsSaveSize) {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -ArgRegsSaveSize,
MachineInstr::FrameSetup);
LastPush = std::prev(MBBI);
DefCFAOffsetCandidates.addInst(LastPush, ArgRegsSaveSize, BeforeFPPush);
}
// Move past area 1.
if (GPRCS1Size > 0) {
GPRCS1Push = LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, GPRCS1Size, BeforeFPPush);
if (FramePtrSpillArea == SpillArea::GPRCS1)
BeforeFPPush = false;
}
// Determine starting offsets of spill areas. These offsets are all positive
// offsets from the bottom of the lowest-addressed callee-save area
// (excluding DPRCS2, which is th the re-aligned stack region) to the bottom
// of the spill area in question.
unsigned FPCXTOffset = NumBytes - ArgRegsSaveSize - FPCXTSaveSize;
unsigned GPRCS1Offset = FPCXTOffset - GPRCS1Size;
unsigned GPRCS2Offset = GPRCS1Offset - GPRCS2Size;
unsigned FPStatusOffset = GPRCS2Offset - FPStatusSize;
Align DPRAlign = DPRCS1Size ? std::min(Align(8), Alignment) : Align(4);
unsigned DPRGapSize = (ArgRegsSaveSize + FPCXTSaveSize + GPRCS1Size +
GPRCS2Size + FPStatusSize) %
DPRAlign.value();
unsigned DPRCS1Offset = FPStatusOffset - DPRGapSize - DPRCS1Size;
if (HasFP) {
// Offset from the CFA to the saved frame pointer, will be negative.
[[maybe_unused]] int FPOffset = MFI.getObjectOffset(FramePtrSpillFI);
LLVM_DEBUG(dbgs() << "FramePtrSpillFI: " << FramePtrSpillFI
<< ", FPOffset: " << FPOffset << "\n");
assert(getMaxFPOffset(STI, *AFI, MF) <= FPOffset &&
"Max FP estimation is wrong");
AFI->setFramePtrSpillOffset(MFI.getObjectOffset(FramePtrSpillFI) +
NumBytes);
}
AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
AFI->setDPRCalleeSavedArea1Offset(DPRCS1Offset);
// Move past area 2.
if (GPRCS2Size > 0) {
assert(PushPopSplit != ARMSubtarget::SplitR11WindowsSEH);
GPRCS2Push = LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, GPRCS2Size, BeforeFPPush);
if (FramePtrSpillArea == SpillArea::GPRCS2)
BeforeFPPush = false;
}
// Move past FP status save area.
if (FPStatusSize > 0) {
while (MBBI != MBB.end()) {
unsigned Opc = MBBI->getOpcode();
if (Opc == ARM::VMRS || Opc == ARM::VMRS_FPEXC)
MBBI++;
else
break;
}
LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, FPStatusSize);
}
// Prolog/epilog inserter assumes we correctly align DPRs on the stack, so our
// .cfi_offset operations will reflect that.
if (DPRGapSize) {
assert(DPRGapSize == 4 && "unexpected alignment requirements for DPRs");
if (LastPush != MBB.end() &&
tryFoldSPUpdateIntoPushPop(STI, MF, &*LastPush, DPRGapSize))
DefCFAOffsetCandidates.addExtraBytes(LastPush, DPRGapSize);
else {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -DPRGapSize,
MachineInstr::FrameSetup);
DefCFAOffsetCandidates.addInst(std::prev(MBBI), DPRGapSize, BeforeFPPush);
}
}
// Move past DPRCS1Size.
if (DPRCS1Size > 0) {
// Since vpush register list cannot have gaps, there may be multiple vpush
// instructions in the prologue.
while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::VSTMDDB_UPD) {
DefCFAOffsetCandidates.addInst(MBBI, sizeOfSPAdjustment(*MBBI),
BeforeFPPush);
DPRCS1Push = LastPush = MBBI++;
}
}
// Move past the aligned DPRCS2 area.
if (DPRCS2Size > 0) {
MBBI = skipAlignedDPRCS2Spills(MBBI, AFI->getNumAlignedDPRCS2Regs());
// The code inserted by emitAlignedDPRCS2Spills realigns the stack, and
// leaves the stack pointer pointing to the DPRCS2 area.
//
// Adjust NumBytes to represent the stack slots below the DPRCS2 area.
NumBytes += MFI.getObjectOffset(D8SpillFI);
} else
NumBytes = DPRCS1Offset;
// Move GPRCS3, if using using SplitR11WindowsSEH.
if (GPRCS3Size > 0) {
assert(PushPopSplit == ARMSubtarget::SplitR11WindowsSEH);
GPRCS3Push = LastPush = MBBI++;
DefCFAOffsetCandidates.addInst(LastPush, GPRCS3Size, BeforeFPPush);
if (FramePtrSpillArea == SpillArea::GPRCS3)
BeforeFPPush = false;
NumBytes -= GPRCS3Size;
}
bool NeedsWinCFIStackAlloc = NeedsWinCFI;
if (PushPopSplit == ARMSubtarget::SplitR11WindowsSEH && HasFP)
NeedsWinCFIStackAlloc = false;
if (STI.isTargetWindows() && WindowsRequiresStackProbe(MF, NumBytes)) {
uint32_t NumWords = NumBytes >> 2;
if (NumWords < 65536) {
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), ARM::R4)
.addImm(NumWords)
.setMIFlags(MachineInstr::FrameSetup)
.add(predOps(ARMCC::AL));
} else {
// Split into two instructions here, instead of using t2MOVi32imm,
// to allow inserting accurate SEH instructions (including accurate
// instruction size for each of them).
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), ARM::R4)
.addImm(NumWords & 0xffff)
.setMIFlags(MachineInstr::FrameSetup)
.add(predOps(ARMCC::AL));
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVTi16), ARM::R4)
.addReg(ARM::R4)
.addImm(NumWords >> 16)
.setMIFlags(MachineInstr::FrameSetup)
.add(predOps(ARMCC::AL));
}
const ARMTargetLowering *TLI = STI.getTargetLowering();
RTLIB::LibcallImpl ChkStkLibcall = TLI->getLibcallImpl(RTLIB::STACK_PROBE);
if (ChkStkLibcall == RTLIB::Unsupported)
reportFatalUsageError("no available implementation of __chkstk");
const char *ChkStk = TLI->getLibcallImplName(ChkStkLibcall).data();
switch (TM.getCodeModel()) {
case CodeModel::Tiny:
llvm_unreachable("Tiny code model not available on ARM.");
case CodeModel::Small:
case CodeModel::Medium:
case CodeModel::Kernel:
BuildMI(MBB, MBBI, dl, TII.get(ARM::tBL))
.add(predOps(ARMCC::AL))
.addExternalSymbol(ChkStk)
.addReg(ARM::R4, RegState::Implicit)
.setMIFlags(MachineInstr::FrameSetup);
break;
case CodeModel::Large:
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R12)
.addExternalSymbol(ChkStk)
.setMIFlags(MachineInstr::FrameSetup);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tBLXr))
.add(predOps(ARMCC::AL))
.addReg(ARM::R12, RegState::Kill)
.addReg(ARM::R4, RegState::Implicit)
.setMIFlags(MachineInstr::FrameSetup);
break;
}
MachineInstrBuilder Instr, SEH;
Instr = BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr), ARM::SP)
.addReg(ARM::SP, RegState::Kill)
.addReg(ARM::R4, RegState::Kill)
.setMIFlags(MachineInstr::FrameSetup)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
if (NeedsWinCFIStackAlloc) {
SEH = BuildMI(MF, dl, TII.get(ARM::SEH_StackAlloc))
.addImm(NumBytes)
.addImm(/*Wide=*/1)
.setMIFlags(MachineInstr::FrameSetup);
MBB.insertAfter(Instr, SEH);
}
NumBytes = 0;
}
if (NumBytes) {
// Adjust SP after all the callee-save spills.
if (AFI->getNumAlignedDPRCS2Regs() == 0 &&
tryFoldSPUpdateIntoPushPop(STI, MF, &*LastPush, NumBytes))
DefCFAOffsetCandidates.addExtraBytes(LastPush, NumBytes);
else {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
DefCFAOffsetCandidates.addInst(std::prev(MBBI), NumBytes);
}
if (HasFP && isARM)
// Restore from fp only in ARM mode: e.g. sub sp, r7, #24
// Note it's not safe to do this in Thumb2 mode because it would have
// taken two instructions:
// mov sp, r7
// sub sp, #24
// If an interrupt is taken between the two instructions, then sp is in
// an inconsistent state (pointing to the middle of callee-saved area).
// The interrupt handler can end up clobbering the registers.
AFI->setShouldRestoreSPFromFP(true);
}
// Set FP to point to the stack slot that contains the previous FP.
// For iOS, FP is R7, which has now been stored in spill area 1.
// Otherwise, if this is not iOS, all the callee-saved registers go
// into spill area 1, including the FP in R11. In either case, it
// is in area one and the adjustment needs to take place just after
// that push.
MachineBasicBlock::iterator AfterPush;
if (HasFP) {
MachineBasicBlock::iterator FPPushInst;
// Offset from SP immediately after the push which saved the FP to the FP
// save slot.
int64_t FPOffsetAfterPush;
switch (FramePtrSpillArea) {
case SpillArea::GPRCS1:
FPPushInst = GPRCS1Push;
FPOffsetAfterPush = MFI.getObjectOffset(FramePtrSpillFI) +
ArgRegsSaveSize + FPCXTSaveSize +
sizeOfSPAdjustment(*FPPushInst);
LLVM_DEBUG(dbgs() << "Frame pointer in GPRCS1, offset "
<< FPOffsetAfterPush << " after that push\n");
break;
case SpillArea::GPRCS2:
FPPushInst = GPRCS2Push;
FPOffsetAfterPush = MFI.getObjectOffset(FramePtrSpillFI) +
ArgRegsSaveSize + FPCXTSaveSize + GPRCS1Size +
sizeOfSPAdjustment(*FPPushInst);
LLVM_DEBUG(dbgs() << "Frame pointer in GPRCS2, offset "
<< FPOffsetAfterPush << " after that push\n");
break;
case SpillArea::GPRCS3:
FPPushInst = GPRCS3Push;
FPOffsetAfterPush = MFI.getObjectOffset(FramePtrSpillFI) +
ArgRegsSaveSize + FPCXTSaveSize + GPRCS1Size +
FPStatusSize + GPRCS2Size + DPRCS1Size + DPRGapSize +
sizeOfSPAdjustment(*FPPushInst);
LLVM_DEBUG(dbgs() << "Frame pointer in GPRCS3, offset "
<< FPOffsetAfterPush << " after that push\n");
break;
default:
llvm_unreachable("frame pointer in unknown spill area");
break;
}
AfterPush = std::next(FPPushInst);
if (PushPopSplit == ARMSubtarget::SplitR11WindowsSEH)
assert(FPOffsetAfterPush == 0);
// Emit the MOV or ADD to set up the frame pointer register.
emitRegPlusImmediate(!AFI->isThumbFunction(), MBB, AfterPush, dl, TII,
FramePtr, ARM::SP, FPOffsetAfterPush,
MachineInstr::FrameSetup);
if (!NeedsWinCFI) {
// Emit DWARF info to find the CFA using the frame pointer from this
// point onward.
CFIInstBuilder CFIBuilder(MBB, AfterPush, MachineInstr::FrameSetup);
if (FPOffsetAfterPush != 0)
CFIBuilder.buildDefCFA(FramePtr, -MFI.getObjectOffset(FramePtrSpillFI));
else
CFIBuilder.buildDefCFARegister(FramePtr);
}
}
// Emit a SEH opcode indicating the prologue end. The rest of the prologue
// instructions below don't need to be replayed to unwind the stack.
if (NeedsWinCFI && MBBI != MBB.begin()) {
MachineBasicBlock::iterator End = MBBI;
if (HasFP && PushPopSplit == ARMSubtarget::SplitR11WindowsSEH)
End = AfterPush;
insertSEHRange(MBB, {}, End, TII, MachineInstr::FrameSetup);
BuildMI(MBB, End, dl, TII.get(ARM::SEH_PrologEnd))
.setMIFlag(MachineInstr::FrameSetup);
MF.setHasWinCFI(true);
}
// Now that the prologue's actual instructions are finalised, we can insert
// the necessary DWARF cf instructions to describe the situation. Start by
// recording where each register ended up:
if (!NeedsWinCFI) {
for (const auto &Entry : reverse(CSI)) {
MCRegister Reg = Entry.getReg();
int FI = Entry.getFrameIdx();
MachineBasicBlock::iterator CFIPos;
switch (getSpillArea(Reg, PushPopSplit, AFI->getNumAlignedDPRCS2Regs(),
RegInfo)) {
case SpillArea::GPRCS1:
CFIPos = std::next(GPRCS1Push);
break;
case SpillArea::GPRCS2:
CFIPos = std::next(GPRCS2Push);
break;
case SpillArea::DPRCS1:
CFIPos = std::next(DPRCS1Push);
break;
case SpillArea::GPRCS3:
CFIPos = std::next(GPRCS3Push);
break;
case SpillArea::FPStatus:
case SpillArea::FPCXT:
case SpillArea::DPRCS2:
// FPCXT and DPRCS2 are not represented in the DWARF info.
break;
}
if (CFIPos.isValid()) {
CFIInstBuilder(MBB, CFIPos, MachineInstr::FrameSetup)
.buildOffset(Reg == ARM::R12 ? ARM::RA_AUTH_CODE : Reg,
MFI.getObjectOffset(FI));
}
}
}
// Now we can emit descriptions of where the canonical frame address was
// throughout the process. If we have a frame pointer, it takes over the job
// half-way through, so only the first few .cfi_def_cfa_offset instructions
// actually get emitted.
if (!NeedsWinCFI) {
LLVM_DEBUG(DefCFAOffsetCandidates.dump());
DefCFAOffsetCandidates.emitDefCFAOffsets(MBB, HasFP);
}
if (STI.isTargetELF() && hasFP(MF))
MFI.setOffsetAdjustment(MFI.getOffsetAdjustment() -
AFI->getFramePtrSpillOffset());
AFI->setFPCXTSaveAreaSize(FPCXTSaveSize);
AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
AFI->setFPStatusSavesSize(FPStatusSize);
AFI->setDPRCalleeSavedGapSize(DPRGapSize);
AFI->setDPRCalleeSavedArea1Size(DPRCS1Size);
AFI->setGPRCalleeSavedArea3Size(GPRCS3Size);
// If we need dynamic stack realignment, do it here. Be paranoid and make
// sure if we also have VLAs, we have a base pointer for frame access.
// If aligned NEON registers were spilled, the stack has already been
// realigned.
if (!AFI->getNumAlignedDPRCS2Regs() && RegInfo->hasStackRealignment(MF)) {
Align MaxAlign = MFI.getMaxAlign();
assert(!AFI->isThumb1OnlyFunction());
if (!AFI->isThumbFunction()) {
emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::SP, MaxAlign,
false);
} else {
// We cannot use sp as source/dest register here, thus we're using r4 to
// perform the calculations. We're emitting the following sequence:
// mov r4, sp
// -- use emitAligningInstructions to produce best sequence to zero
// -- out lower bits in r4
// mov sp, r4
// FIXME: It will be better just to find spare register here.
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4)
.addReg(ARM::SP, RegState::Kill)
.add(predOps(ARMCC::AL));
emitAligningInstructions(MF, AFI, TII, MBB, MBBI, dl, ARM::R4, MaxAlign,
false);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(ARM::R4, RegState::Kill)
.add(predOps(ARMCC::AL));
}
AFI->setShouldRestoreSPFromFP(true);
}
// If we need a base pointer, set it up here. It's whatever the value
// of the stack pointer is at this point. Any variable size objects
// will be allocated after this, so we can still use the base pointer
// to reference locals.
// FIXME: Clarify FrameSetup flags here.
if (RegInfo->hasBasePointer(MF) && !MBB.isEHFuncletEntry()) {
if (isARM)
BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), RegInfo->getBaseRegister())
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
else
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), RegInfo->getBaseRegister())
.addReg(ARM::SP)
.add(predOps(ARMCC::AL));
}
// If the frame has variable sized objects then the epilogue must restore
// the sp from fp. We can assume there's an FP here since hasFP already
// checks for hasVarSizedObjects.
if (MFI.hasVarSizedObjects())
AFI->setShouldRestoreSPFromFP(true);
}
void ARMFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineFrameInfo &MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
assert(!AFI->isThumb1OnlyFunction() &&
"This emitEpilogue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
ARMSubtarget::PushPopSplitVariation PushPopSplit =
STI.getPushPopSplitVariation(MF);
LLVM_DEBUG(dbgs() << "Emitting epilogue for " << MF.getName() << "\n");
// Amount of stack space we reserved next to incoming args for either
// varargs registers or stack arguments in tail calls made by this function.
unsigned ReservedArgStack = AFI->getArgRegsSaveSize();
// How much of the stack used by incoming arguments this function is expected
// to restore in this particular epilogue.
int IncomingArgStackToRestore = getArgumentStackToRestore(MF, MBB);
int NumBytes = (int)MFI.getStackSize();
Register FramePtr = RegInfo->getFrameRegister(MF);
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction().getCallingConv() == CallingConv::GHC)
return;
// First put ourselves on the first (from top) terminator instructions.
MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
MachineBasicBlock::iterator RangeStart;
if (!AFI->hasStackFrame()) {
if (MF.hasWinCFI()) {
BuildMI(MBB, MBBI, dl, TII.get(ARM::SEH_EpilogStart))
.setMIFlag(MachineInstr::FrameDestroy);
RangeStart = initMBBRange(MBB, MBBI);
}
if (NumBytes + IncomingArgStackToRestore != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII,
NumBytes + IncomingArgStackToRestore,
MachineInstr::FrameDestroy);
} else {
// Unwind MBBI to point to first LDR / VLDRD.
if (MBBI != MBB.begin()) {
do {
--MBBI;
} while (MBBI != MBB.begin() &&
MBBI->getFlag(MachineInstr::FrameDestroy));
if (!MBBI->getFlag(MachineInstr::FrameDestroy))
++MBBI;
}
if (MF.hasWinCFI()) {
BuildMI(MBB, MBBI, dl, TII.get(ARM::SEH_EpilogStart))
.setMIFlag(MachineInstr::FrameDestroy);
RangeStart = initMBBRange(MBB, MBBI);
}
// Move SP to start of FP callee save spill area.
NumBytes -=
(ReservedArgStack + AFI->getFPCXTSaveAreaSize() +
AFI->getGPRCalleeSavedArea1Size() + AFI->getGPRCalleeSavedArea2Size() +
AFI->getFPStatusSavesSize() + AFI->getDPRCalleeSavedGapSize() +
AFI->getDPRCalleeSavedArea1Size() + AFI->getGPRCalleeSavedArea3Size());
// Reset SP based on frame pointer only if the stack frame extends beyond
// frame pointer stack slot or target is ELF and the function has FP.
if (AFI->shouldRestoreSPFromFP()) {
NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
if (NumBytes) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, FramePtr, -NumBytes,
ARMCC::AL, 0, TII,
MachineInstr::FrameDestroy);
else {
// It's not possible to restore SP from FP in a single instruction.
// For iOS, this looks like:
// mov sp, r7
// sub sp, #24
// This is bad, if an interrupt is taken after the mov, sp is in an
// inconsistent state.
// Use the first callee-saved register as a scratch register.
assert(!MFI.getPristineRegs(MF).test(ARM::R4) &&
"No scratch register to restore SP from FP!");
emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
ARMCC::AL, 0, TII, MachineInstr::FrameDestroy);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(ARM::R4)
.add(predOps(ARMCC::AL))
.setMIFlag(MachineInstr::FrameDestroy);
}
} else {
// Thumb2 or ARM.
if (isARM)
BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), ARM::SP)
.addReg(FramePtr)
.add(predOps(ARMCC::AL))
.add(condCodeOp())
.setMIFlag(MachineInstr::FrameDestroy);
else
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(FramePtr)
.add(predOps(ARMCC::AL))
.setMIFlag(MachineInstr::FrameDestroy);
}
} else if (NumBytes &&
!tryFoldSPUpdateIntoPushPop(STI, MF, &*MBBI, NumBytes))
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes,
MachineInstr::FrameDestroy);
// Increment past our save areas.
if (AFI->getGPRCalleeSavedArea3Size()) {
assert(PushPopSplit == ARMSubtarget::SplitR11WindowsSEH);
(void)PushPopSplit;
MBBI++;
}
if (MBBI != MBB.end() && AFI->getDPRCalleeSavedArea1Size()) {
MBBI++;
// Since vpop register list cannot have gaps, there may be multiple vpop
// instructions in the epilogue.
while (MBBI != MBB.end() && MBBI->getOpcode() == ARM::VLDMDIA_UPD)
MBBI++;
}
if (AFI->getDPRCalleeSavedGapSize()) {
assert(AFI->getDPRCalleeSavedGapSize() == 4 &&
"unexpected DPR alignment gap");
emitSPUpdate(isARM, MBB, MBBI, dl, TII, AFI->getDPRCalleeSavedGapSize(),
MachineInstr::FrameDestroy);
}
if (AFI->getGPRCalleeSavedArea2Size()) {
assert(PushPopSplit != ARMSubtarget::SplitR11WindowsSEH);
(void)PushPopSplit;
MBBI++;
}
if (AFI->getGPRCalleeSavedArea1Size()) MBBI++;
if (ReservedArgStack || IncomingArgStackToRestore) {
assert((int)ReservedArgStack + IncomingArgStackToRestore >= 0 &&
"attempting to restore negative stack amount");
emitSPUpdate(isARM, MBB, MBBI, dl, TII,
ReservedArgStack + IncomingArgStackToRestore,
MachineInstr::FrameDestroy);
}
// Validate PAC, It should have been already popped into R12. For CMSE entry
// function, the validation instruction is emitted during expansion of the
// tBXNS_RET, since the validation must use the value of SP at function
// entry, before saving, resp. after restoring, FPCXTNS.
if (AFI->shouldSignReturnAddress() && !AFI->isCmseNSEntryFunction()) {
bool CanUseBXAut =
STI.isThumb() && STI.hasV8_1MMainlineOps() && STI.hasPACBTI();
auto TMBBI = MBB.getFirstTerminator();
bool IsBXReturn =
TMBBI != MBB.end() && TMBBI->getOpcode() == ARM::tBX_RET;
if (IsBXReturn && CanUseBXAut)
TMBBI->setDesc(STI.getInstrInfo()->get(ARM::t2BXAUT_RET));
else
BuildMI(MBB, MBBI, DebugLoc(), STI.getInstrInfo()->get(ARM::t2AUT));
}
}
if (MF.hasWinCFI()) {
insertSEHRange(MBB, RangeStart, MBB.end(), TII, MachineInstr::FrameDestroy);
BuildMI(MBB, MBB.end(), dl, TII.get(ARM::SEH_EpilogEnd))
.setMIFlag(MachineInstr::FrameDestroy);
}
}
/// getFrameIndexReference - Provide a base+offset reference to an FI slot for
/// debug info. It's the same as what we use for resolving the code-gen
/// references for now. FIXME: This can go wrong when references are
/// SP-relative and simple call frames aren't used.
StackOffset ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF,
int FI,
Register &FrameReg) const {
return StackOffset::getFixed(ResolveFrameIndexReference(MF, FI, FrameReg, 0));
}
StackOffset
ARMFrameLowering::getNonLocalFrameIndexReference(const MachineFunction &MF,
int FI) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
int Offset = MFI.getObjectOffset(FI) + MFI.getStackSize();
return StackOffset::getFixed(Offset);
}
int ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
int FI, Register &FrameReg,
int SPAdj) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int Offset = MFI.getObjectOffset(FI) + MFI.getStackSize();
int FPOffset = Offset - AFI->getFramePtrSpillOffset();
bool isFixed = MFI.isFixedObjectIndex(FI);
FrameReg = ARM::SP;
Offset += SPAdj;
// SP can move around if there are allocas. We may also lose track of SP
// when emergency spilling inside a non-reserved call frame setup.
bool hasMovingSP = !hasReservedCallFrame(MF);
// When dynamically realigning the stack, use the frame pointer for
// parameters, and the stack/base pointer for locals.
if (RegInfo->hasStackRealignment(MF)) {
assert(hasFP(MF) && "dynamic stack realignment without a FP!");
if (isFixed) {
FrameReg = RegInfo->getFrameRegister(MF);
Offset = FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) &&
"VLAs and dynamic stack alignment, but missing base pointer!");
FrameReg = RegInfo->getBaseRegister();
Offset -= SPAdj;
}
return Offset;
}
// If there is a frame pointer, use it when we can.
if (hasFP(MF) && AFI->hasStackFrame()) {
// Use frame pointer to reference fixed objects. Use it for locals if
// there are VLAs (and thus the SP isn't reliable as a base).
if (isFixed || (hasMovingSP && !RegInfo->hasBasePointer(MF))) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) && "missing base pointer!");
if (AFI->isThumb2Function()) {
// Try to use the frame pointer if we can, else use the base pointer
// since it's available. This is handy for the emergency spill slot, in
// particular.
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
} else if (AFI->isThumbFunction()) {
// Prefer SP to base pointer, if the offset is suitably aligned and in
// range as the effective range of the immediate offset is bigger when
// basing off SP.
// Use add <rd>, sp, #<imm8>
// ldr <rd>, [sp, #<imm8>]
if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020)
return Offset;
// In Thumb2 mode, the negative offset is very limited. Try to avoid
// out of range references. ldr <rt>,[<rn>, #-<imm8>]
if (AFI->isThumb2Function() && FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
} else if (Offset > (FPOffset < 0 ? -FPOffset : FPOffset)) {
// Otherwise, use SP or FP, whichever is closer to the stack slot.
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
// Use the base pointer if we have one.
// FIXME: Maybe prefer sp on Thumb1 if it's legal and the offset is cheaper?
// That can happen if we forced a base pointer for a large call frame.
if (RegInfo->hasBasePointer(MF)) {
FrameReg = RegInfo->getBaseRegister();
Offset -= SPAdj;
}
return Offset;
}
void ARMFrameLowering::emitPushInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
ArrayRef<CalleeSavedInfo> CSI,
unsigned StmOpc, unsigned StrOpc,
bool NoGap,
function_ref<bool(unsigned)> Func) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
DebugLoc DL;
using RegAndKill = std::pair<unsigned, bool>;
SmallVector<RegAndKill, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
for (; i != 0; --i) {
MCRegister Reg = CSI[i-1].getReg();
if (!Func(Reg))
continue;
const MachineRegisterInfo &MRI = MF.getRegInfo();
bool isLiveIn = MRI.isLiveIn(Reg);
if (!isLiveIn && !MRI.isReserved(Reg))
MBB.addLiveIn(Reg);
// If NoGap is true, push consecutive registers and then leave the rest
// for other instructions. e.g.
// vpush {d8, d10, d11} -> vpush {d8}, vpush {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
// Do not set a kill flag on values that are also marked as live-in. This
// happens with the @llvm-returnaddress intrinsic and with arguments
// passed in callee saved registers.
// Omitting the kill flags is conservatively correct even if the live-in
// is not used after all.
Regs.push_back(std::make_pair(Reg, /*isKill=*/!isLiveIn));
}
if (Regs.empty())
continue;
llvm::sort(Regs, [&](const RegAndKill &LHS, const RegAndKill &RHS) {
return TRI.getEncodingValue(LHS.first) < TRI.getEncodingValue(RHS.first);
});
if (Regs.size() > 1 || StrOpc== 0) {
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(StmOpc), ARM::SP)
.addReg(ARM::SP)
.setMIFlags(MachineInstr::FrameSetup)
.add(predOps(ARMCC::AL));
for (const auto &[Reg, Kill] : Regs)
MIB.addReg(Reg, getKillRegState(Kill));
} else if (Regs.size() == 1) {
BuildMI(MBB, MI, DL, TII.get(StrOpc), ARM::SP)
.addReg(Regs[0].first, getKillRegState(Regs[0].second))
.addReg(ARM::SP)
.setMIFlags(MachineInstr::FrameSetup)
.addImm(-4)
.add(predOps(ARMCC::AL));
}
Regs.clear();
// Put any subsequent vpush instructions before this one: they will refer to
// higher register numbers so need to be pushed first in order to preserve
// monotonicity.
if (MI != MBB.begin())
--MI;
}
}
void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
MutableArrayRef<CalleeSavedInfo> CSI,
unsigned LdmOpc, unsigned LdrOpc,
bool isVarArg, bool NoGap,
function_ref<bool(unsigned)> Func) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
bool hasPAC = AFI->shouldSignReturnAddress();
DebugLoc DL;
bool isTailCall = false;
bool isInterrupt = false;
bool isTrap = false;
bool isCmseEntry = false;
ARMSubtarget::PushPopSplitVariation PushPopSplit =
STI.getPushPopSplitVariation(MF);
if (MBB.end() != MI) {
DL = MI->getDebugLoc();
unsigned RetOpcode = MI->getOpcode();
isTailCall =
(RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNri ||
RetOpcode == ARM::TCRETURNrinotr12);
isInterrupt =
RetOpcode == ARM::SUBS_PC_LR || RetOpcode == ARM::t2SUBS_PC_LR;
isTrap = RetOpcode == ARM::TRAP || RetOpcode == ARM::tTRAP;
isCmseEntry = (RetOpcode == ARM::tBXNS || RetOpcode == ARM::tBXNS_RET);
}
SmallVector<unsigned, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
bool DeleteRet = false;
for (; i != 0; --i) {
CalleeSavedInfo &Info = CSI[i-1];
MCRegister Reg = Info.getReg();
if (!Func(Reg))
continue;
if (Reg == ARM::LR && !isTailCall && !isVarArg && !isInterrupt &&
!isCmseEntry && !isTrap && AFI->getArgumentStackToRestore() == 0 &&
STI.hasV5TOps() && MBB.succ_empty() && !hasPAC &&
(PushPopSplit != ARMSubtarget::SplitR11WindowsSEH &&
PushPopSplit != ARMSubtarget::SplitR11AAPCSSignRA)) {
Reg = ARM::PC;
// Fold the return instruction into the LDM.
DeleteRet = true;
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
}
// If NoGap is true, pop consecutive registers and then leave the rest
// for other instructions. e.g.
// vpop {d8, d10, d11} -> vpop {d8}, vpop {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
Regs.push_back(Reg);
}
if (Regs.empty())
continue;
llvm::sort(Regs, [&](unsigned LHS, unsigned RHS) {
return TRI.getEncodingValue(LHS) < TRI.getEncodingValue(RHS);
});
if (Regs.size() > 1 || LdrOpc == 0) {
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(LdmOpc), ARM::SP)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameDestroy);
for (unsigned Reg : Regs)
MIB.addReg(Reg, getDefRegState(true));
if (DeleteRet) {
if (MI != MBB.end()) {
MIB.copyImplicitOps(*MI);
MI->eraseFromParent();
}
}
MI = MIB;
} else if (Regs.size() == 1) {
// If we adjusted the reg to PC from LR above, switch it back here. We
// only do that for LDM.
if (Regs[0] == ARM::PC)
Regs[0] = ARM::LR;
MachineInstrBuilder MIB =
BuildMI(MBB, MI, DL, TII.get(LdrOpc), Regs[0])
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.setMIFlags(MachineInstr::FrameDestroy);
// ARM mode needs an extra reg0 here due to addrmode2. Will go away once
// that refactoring is complete (eventually).
if (LdrOpc == ARM::LDR_POST_REG || LdrOpc == ARM::LDR_POST_IMM) {
MIB.addReg(0);
MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::add, 4, ARM_AM::no_shift));
} else
MIB.addImm(4);
MIB.add(predOps(ARMCC::AL));
}
Regs.clear();
// Put any subsequent vpop instructions after this one: they will refer to
// higher register numbers so need to be popped afterwards.
if (MI != MBB.end())
++MI;
}
}
void ARMFrameLowering::emitFPStatusSaves(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
ArrayRef<CalleeSavedInfo> CSI,
unsigned PushOpc) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
SmallVector<MCRegister> Regs;
auto RegPresent = [&CSI](MCRegister Reg) {
return llvm::any_of(CSI, [Reg](const CalleeSavedInfo &C) {
return C.getReg() == Reg;
});
};
// If we need to save FPSCR, then we must move FPSCR into R4 with the VMRS
// instruction.
if (RegPresent(ARM::FPSCR)) {
BuildMI(MBB, MI, DebugLoc(), TII.get(ARM::VMRS), ARM::R4)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameSetup);
Regs.push_back(ARM::R4);
}
// If we need to save FPEXC, then we must move FPEXC into R5 with the
// VMRS_FPEXC instruction.
if (RegPresent(ARM::FPEXC)) {
BuildMI(MBB, MI, DebugLoc(), TII.get(ARM::VMRS_FPEXC), ARM::R5)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameSetup);
Regs.push_back(ARM::R5);
}
// If neither FPSCR and FPEXC are present, then do nothing.
if (Regs.size() == 0)
return;
// Push both R4 and R5 onto the stack, if present.
MachineInstrBuilder MIB =
BuildMI(MBB, MI, DebugLoc(), TII.get(PushOpc), ARM::SP)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameSetup);
for (Register Reg : Regs) {
MIB.addReg(Reg);
}
}
void ARMFrameLowering::emitFPStatusRestores(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
MutableArrayRef<CalleeSavedInfo> CSI, unsigned LdmOpc) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
auto RegPresent = [&CSI](MCRegister Reg) {
return llvm::any_of(CSI, [Reg](const CalleeSavedInfo &C) {
return C.getReg() == Reg;
});
};
// Do nothing if we don't need to restore any FP status registers.
if (!RegPresent(ARM::FPSCR) && !RegPresent(ARM::FPEXC))
return;
// Pop registers off of the stack.
MachineInstrBuilder MIB =
BuildMI(MBB, MI, DebugLoc(), TII.get(LdmOpc), ARM::SP)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameDestroy);
// If FPSCR was saved, it will be popped into R4.
if (RegPresent(ARM::FPSCR)) {
MIB.addReg(ARM::R4, RegState::Define);
}
// If FPEXC was saved, it will be popped into R5.
if (RegPresent(ARM::FPEXC)) {
MIB.addReg(ARM::R5, RegState::Define);
}
// Move the FPSCR value back into the register with the VMSR instruction.
if (RegPresent(ARM::FPSCR)) {
BuildMI(MBB, MI, DebugLoc(), STI.getInstrInfo()->get(ARM::VMSR))
.addReg(ARM::R4)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameDestroy);
}
// Move the FPEXC value back into the register with the VMSR_FPEXC
// instruction.
if (RegPresent(ARM::FPEXC)) {
BuildMI(MBB, MI, DebugLoc(), STI.getInstrInfo()->get(ARM::VMSR_FPEXC))
.addReg(ARM::R5)
.add(predOps(ARMCC::AL))
.setMIFlags(MachineInstr::FrameDestroy);
}
}
/// Emit aligned spill instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. Also insert stack realignment code and leave the stack
/// pointer pointing to the d8 spill slot.
static void emitAlignedDPRCS2Spills(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
ArrayRef<CalleeSavedInfo> CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
MachineFrameInfo &MFI = MF.getFrameInfo();
// Mark the D-register spill slots as properly aligned. Since MFI computes
// stack slot layout backwards, this can actually mean that the d-reg stack
// slot offsets can be wrong. The offset for d8 will always be correct.
for (const CalleeSavedInfo &I : CSI) {
unsigned DNum = I.getReg() - ARM::D8;
if (DNum > NumAlignedDPRCS2Regs - 1)
continue;
int FI = I.getFrameIdx();
// The even-numbered registers will be 16-byte aligned, the odd-numbered
// registers will be 8-byte aligned.
MFI.setObjectAlignment(FI, DNum % 2 ? Align(8) : Align(16));
// The stack slot for D8 needs to be maximally aligned because this is
// actually the point where we align the stack pointer. MachineFrameInfo
// computes all offsets relative to the incoming stack pointer which is a
// bit weird when realigning the stack. Any extra padding for this
// over-alignment is not realized because the code inserted below adjusts
// the stack pointer by numregs * 8 before aligning the stack pointer.
if (DNum == 0)
MFI.setObjectAlignment(FI, MFI.getMaxAlign());
}
// Move the stack pointer to the d8 spill slot, and align it at the same
// time. Leave the stack slot address in the scratch register r4.
//
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
//
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
AFI->setShouldRestoreSPFromFP(true);
// sub r4, sp, #numregs * 8
// The immediate is <= 64, so it doesn't need any special encoding.
unsigned Opc = isThumb ? ARM::t2SUBri : ARM::SUBri;
BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addReg(ARM::SP)
.addImm(8 * NumAlignedDPRCS2Regs)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
Align MaxAlign = MF.getFrameInfo().getMaxAlign();
// We must set parameter MustBeSingleInstruction to true, since
// skipAlignedDPRCS2Spills expects exactly 3 instructions to perform
// stack alignment. Luckily, this can always be done since all ARM
// architecture versions that support Neon also support the BFC
// instruction.
emitAligningInstructions(MF, AFI, TII, MBB, MI, DL, ARM::R4, MaxAlign, true);
// mov sp, r4
// The stack pointer must be adjusted before spilling anything, otherwise
// the stack slots could be clobbered by an interrupt handler.
// Leave r4 live, it is used below.
Opc = isThumb ? ARM::tMOVr : ARM::MOVr;
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(Opc), ARM::SP)
.addReg(ARM::R4)
.add(predOps(ARMCC::AL));
if (!isThumb)
MIB.add(condCodeOp());
// Now spill NumAlignedDPRCS2Regs registers starting from d8.
// r4 holds the stack slot address.
unsigned NextReg = ARM::D8;
// 16-byte aligned vst1.64 with 4 d-regs and address writeback.
// The writeback is only needed when emitting two vst1.64 instructions.
if (NumAlignedDPRCS2Regs >= 6) {
MCRegister SupReg =
TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, &ARM::QQPRRegClass);
MBB.addLiveIn(SupReg);
BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Qwb_fixed), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(16)
.addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vst1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
MCRegister SupReg =
TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, &ARM::QQPRRegClass);
MBB.addLiveIn(SupReg);
BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Q))
.addReg(ARM::R4)
.addImm(16)
.addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vst1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
MCRegister SupReg =
TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, &ARM::QPRRegClass);
MBB.addLiveIn(SupReg);
BuildMI(MBB, MI, DL, TII.get(ARM::VST1q64))
.addReg(ARM::R4)
.addImm(16)
.addReg(SupReg)
.add(predOps(ARMCC::AL));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vstr.64 for the odd last register.
if (NumAlignedDPRCS2Regs) {
MBB.addLiveIn(NextReg);
// vstr.64 uses addrmode5 which has an offset scale of 4.
BuildMI(MBB, MI, DL, TII.get(ARM::VSTRD))
.addReg(NextReg)
.addReg(ARM::R4)
.addImm((NextReg - R4BaseReg) * 2)
.add(predOps(ARMCC::AL));
}
// The last spill instruction inserted should kill the scratch register r4.
std::prev(MI)->addRegisterKilled(ARM::R4, TRI);
}
/// Skip past the code inserted by emitAlignedDPRCS2Spills, and return an
/// iterator to the following instruction.
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs) {
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
++MI; ++MI; ++MI;
assert(MI->mayStore() && "Expecting spill instruction");
// These switches all fall through.
switch(NumAlignedDPRCS2Regs) {
case 7:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
[[fallthrough]];
default:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
[[fallthrough]];
case 1:
case 2:
case 4:
assert(MI->killsRegister(ARM::R4, /*TRI=*/nullptr) && "Missed kill flag");
++MI;
}
return MI;
}
/// Emit aligned reload instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. These instructions are assumed to execute while the
/// stack is still aligned, unlike the code inserted by emitPopInst.
static void emitAlignedDPRCS2Restores(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
ArrayRef<CalleeSavedInfo> CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI != MBB.end() ? MI->getDebugLoc() : DebugLoc();
const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
// Find the frame index assigned to d8.
int D8SpillFI = 0;
for (const CalleeSavedInfo &I : CSI)
if (I.getReg() == ARM::D8) {
D8SpillFI = I.getFrameIdx();
break;
}
// Materialize the address of the d8 spill slot into the scratch register r4.
// This can be fairly complicated if the stack frame is large, so just use
// the normal frame index elimination mechanism to do it. This code runs as
// the initial part of the epilog where the stack and base pointers haven't
// been changed yet.
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
unsigned Opc = isThumb ? ARM::t2ADDri : ARM::ADDri;
BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addFrameIndex(D8SpillFI)
.addImm(0)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
// Now restore NumAlignedDPRCS2Regs registers starting from d8.
unsigned NextReg = ARM::D8;
// 16-byte aligned vld1.64 with 4 d-regs and writeback.
if (NumAlignedDPRCS2Regs >= 6) {
MCRegister SupReg =
TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, &ARM::QQPRRegClass);
BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Qwb_fixed), NextReg)
.addReg(ARM::R4, RegState::Define)
.addReg(ARM::R4, RegState::Kill)
.addImm(16)
.addReg(SupReg, RegState::ImplicitDefine)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vld1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
MCRegister SupReg =
TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, &ARM::QQPRRegClass);
BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Q), NextReg)
.addReg(ARM::R4)
.addImm(16)
.addReg(SupReg, RegState::ImplicitDefine)
.add(predOps(ARMCC::AL));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vld1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
MCRegister SupReg =
TRI->getMatchingSuperReg(NextReg, ARM::dsub_0, &ARM::QPRRegClass);
BuildMI(MBB, MI, DL, TII.get(ARM::VLD1q64), SupReg)
.addReg(ARM::R4)
.addImm(16)
.add(predOps(ARMCC::AL));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vldr.64 for the remaining odd register.
if (NumAlignedDPRCS2Regs)
BuildMI(MBB, MI, DL, TII.get(ARM::VLDRD), NextReg)
.addReg(ARM::R4)
.addImm(2 * (NextReg - R4BaseReg))
.add(predOps(ARMCC::AL));
// Last store kills r4.
std::prev(MI)->addRegisterKilled(ARM::R4, TRI);
}
bool ARMFrameLowering::spillCalleeSavedRegisters(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
ARMSubtarget::PushPopSplitVariation PushPopSplit =
STI.getPushPopSplitVariation(MF);
const ARMBaseRegisterInfo *RegInfo = STI.getRegisterInfo();
unsigned PushOpc = AFI->isThumbFunction() ? ARM::t2STMDB_UPD : ARM::STMDB_UPD;
unsigned PushOneOpc = AFI->isThumbFunction() ?
ARM::t2STR_PRE : ARM::STR_PRE_IMM;
unsigned FltOpc = ARM::VSTMDDB_UPD;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
// Compute PAC in R12.
if (AFI->shouldSignReturnAddress()) {
BuildMI(MBB, MI, DebugLoc(), STI.getInstrInfo()->get(ARM::t2PAC))
.setMIFlags(MachineInstr::FrameSetup);
}
// Save the non-secure floating point context.
if (llvm::any_of(CSI, [](const CalleeSavedInfo &C) {
return C.getReg() == ARM::FPCXTNS;
})) {
BuildMI(MBB, MI, DebugLoc(), STI.getInstrInfo()->get(ARM::VSTR_FPCXTNS_pre),
ARM::SP)
.addReg(ARM::SP)
.addImm(-4)
.add(predOps(ARMCC::AL));
}
auto CheckRegArea = [PushPopSplit, NumAlignedDPRCS2Regs,
RegInfo](unsigned Reg, SpillArea TestArea) {
return getSpillArea(Reg, PushPopSplit, NumAlignedDPRCS2Regs, RegInfo) ==
TestArea;
};
auto IsGPRCS1 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::GPRCS1);
};
auto IsGPRCS2 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::GPRCS2);
};
auto IsDPRCS1 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::DPRCS1);
};
auto IsGPRCS3 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::GPRCS3);
};
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, IsGPRCS1);
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, IsGPRCS2);
emitFPStatusSaves(MBB, MI, CSI, PushOpc);
emitPushInst(MBB, MI, CSI, FltOpc, 0, true, IsDPRCS1);
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, IsGPRCS3);
// The code above does not insert spill code for the aligned DPRCS2 registers.
// The stack realignment code will be inserted between the push instructions
// and these spills.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Spills(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
return true;
}
bool ARMFrameLowering::restoreCalleeSavedRegisters(
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
MutableArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const ARMBaseRegisterInfo *RegInfo = STI.getRegisterInfo();
bool isVarArg = AFI->getArgRegsSaveSize() > 0;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
ARMSubtarget::PushPopSplitVariation PushPopSplit =
STI.getPushPopSplitVariation(MF);
// The emitPopInst calls below do not insert reloads for the aligned DPRCS2
// registers. Do that here instead.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Restores(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
unsigned PopOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
unsigned LdrOpc =
AFI->isThumbFunction() ? ARM::t2LDR_POST : ARM::LDR_POST_IMM;
unsigned FltOpc = ARM::VLDMDIA_UPD;
auto CheckRegArea = [PushPopSplit, NumAlignedDPRCS2Regs,
RegInfo](unsigned Reg, SpillArea TestArea) {
return getSpillArea(Reg, PushPopSplit, NumAlignedDPRCS2Regs, RegInfo) ==
TestArea;
};
auto IsGPRCS1 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::GPRCS1);
};
auto IsGPRCS2 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::GPRCS2);
};
auto IsDPRCS1 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::DPRCS1);
};
auto IsGPRCS3 = [&CheckRegArea](unsigned Reg) {
return CheckRegArea(Reg, SpillArea::GPRCS3);
};
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false, IsGPRCS3);
emitPopInst(MBB, MI, CSI, FltOpc, 0, isVarArg, true, IsDPRCS1);
emitFPStatusRestores(MBB, MI, CSI, PopOpc);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false, IsGPRCS2);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false, IsGPRCS1);
return true;
}
// FIXME: Make generic?
static unsigned EstimateFunctionSizeInBytes(const MachineFunction &MF,
const ARMBaseInstrInfo &TII,
const ARMSubtarget &STI,
const ARMBaseRegisterInfo *RegInfo,
BitVector &SavedRegs,
bool BigFrameOffsets) {
unsigned FnSize = 0;
bool KCFI = MF.getFunction().getParent()->getModuleFlag("kcfi");
if (MF.shouldSplitStack()) {
// Split stack prologue saves r4,r5; makes a copy of sp and loads
// a literal; compares the two, and if sp < literal, pushes
// further registers and calls __morestack.
FnSize += 0x24;
}
// Count the number of saved high registers, which take more effort
// to push and pop in the prologue and epilogue.
unsigned SavedHighRegs = 0;
for (auto Reg : {ARM::R8, ARM::R9, ARM::R10, ARM::R11, ARM::R12})
if (SavedRegs.test(Reg))
++SavedHighRegs;
// Size of a particularly large Thumb1 stack setup prologue:
// update sp for variadic functions (2 bytes)
// + push registers (2 bytes for PUSH {low regs} + 4 bytes per high register
// that needs to be copied into a low reg and then pushed)
// + frame pointer (might use r11, requiring pushing it first, 6 bytes)
// + stack update (up to 12 bytes if a constant load is needed and a branch
// required later to skip the constant)
// + stack realignment (8, if needed)
// + make base pointer (2).
unsigned PrologueSize = 2 + 4 * SavedHighRegs + 6 + 12 + 2;
if (RegInfo->hasStackRealignment(MF))
PrologueSize += 8;
FnSize += PrologueSize;
// Size of a large epilogue:
// restore sp from frame pointer (6 bytes if it's in r11)
// + pop registers (2 bytes + 4 per high register, as above)
// + pop r11 if it was saved to make frame pointer (4 bytes)
// + pop return address into a low reg (2 bytes)
// + update sp to undo variadic function setup (2 bytes)
// + BX to where you popped the return address (2 bytes)
unsigned EpilogueSize = 6 + 2 + 4 * SavedHighRegs + 4 + 2 + 2;
bool FirstBlock = true;
for (auto &MBB : MF) {
if (!FirstBlock) {
// We might have to insert padding to align the start of this basic
// block.
unsigned Alignment = MBB.getMaxBytesForAlignment();
FnSize += Alignment;
}
unsigned SizeBeforeThisBB = FnSize;
bool seenBranch = false, seenConstantLoad = false;
for (auto &MI : MBB) {
unsigned InstSize;
switch (MI.getOpcode()) {
case ARM::tADDframe:
if (BigFrameOffsets)
// We might need two ADD instructions, or even a constant
// load. In the latter case we must count the constant as
// well as the load instruction and the addition, for 8
// bytes total.
InstSize = 8;
else
InstSize = 2;
break;
case ARM::tLDRspi:
case ARM::tSTRspi:
if (BigFrameOffsets)
// In a really nasty case, accessing a stack slot might
// require saving and restoring a scratch register (4 bytes)
// to make space to load (2 bytes) a constant (4 bytes) to
// add to SP or FP (2 bytes) and then do the load/store to
// the resulting register (2 bytes).
InstSize = 14;
else
InstSize = 2;
break;
case TargetOpcode::COPY:
// In some situations, COPY has to go via a high register, to
// avoid corrupting the PSR flags: Thumb moves between low and
// high registers don't write the PSR, whereas low/low moves
// do.
InstSize = 4; // may have to go via a high reg
break;
case ARM::MEMCPY:
InstSize = 4; // becomes one LDMIA_UPD + STMIA_UPD pair
break;
case ARM::Int_eh_sjlj_dispatchsetup:
// Worst case is 6 bytes, loading a constant from a literal pool.
InstSize = 6;
break;
case ARM::tLDRpci_pic:
InstSize = 4; // ordinary LDRpci + add to pc
break;
case ARM::ADJCALLSTACKDOWN:
case ARM::ADJCALLSTACKUP:
InstSize = 2;
break;
case ARM::tBLXNS_CALL:
// A call across a CMSE trust boundary involves a lot of work. We must
// clear all the registers that might contain our own secrets, which
// means pushing them first. So first push low registers, then move
// four high regs into them and push those too.
InstSize = 2 + 2 * 4 + 2;
// Then we must clear the low bit of the target register, because
// instead of indicating Arm/Thumb it indicates the CMSE security
// status. That takes two instructions.
InstSize += 4;
// Now actually clear all the registers, via a MOV for each one. This
// includes argument registers as well as saved regs, so it can be
// r1-r12 inclusive.
InstSize += 2 * 12;
// Clear the PSR flags (a wide instruction even in Armv8-M Baseline).
InstSize += 4;
// Perform the BLXNS call itself.
InstSize += 2;
// Now pop all the saved registers, which takes the same amount of
// effort as pushing them did.
InstSize += 2 + 2 * 4 + 2;
break;
case ARM::tBXNS_RET:
// When returning across a CMSE boundary, we must potentially clear all
// the registers that we haven't restored to the caller's value: r0-r3
// and r12. We also clear the PSR flags, and finally return via BXNS.
InstSize = 5 * 2 + 4 + 2;
break;
case TargetOpcode::LOAD_STACK_GUARD:
if (STI.genExecuteOnly())
// In execute-only code generation, it costs seven 2-byte
// instructions (MOV + 3 ADD + 3 LSL) to load an arbitrary
// 32-bit constant, plus two 4-byte MSRs to save/restore the
// flags those instructions clobber. Then we load from the
// resulting address with one more 2-byte instruction.
InstSize = 7 * 2 + 2 * 4 + 8;
else
// If we're not generating execute-only code, the constant
// just costs an LDR and a literal, and then another LDR is
// needed to load from that address.
InstSize = 2 * 2 + 4;
break;
default:
InstSize = TII.getInstSizeInBytes(MI);
break;
}
FnSize += InstSize;
// If the instruction loads a constant, score the size of the
// constant, in case it can't be shared with other basic blocks.
for (MachineMemOperand *MO : MI.memoperands()) {
const PseudoSourceValue *PSV =
dyn_cast_if_present<const PseudoSourceValue *>(
MO->getPointerInfo().V);
if (PSV && PSV->kind() == PseudoSourceValue::ConstantPool) {
unsigned ConstSize = MO->getType().getSizeInBytes();
FnSize += ConstSize;
seenConstantLoad = true;
}
}
// If the instruction is a return or a tailcall, count the size
// of an epilogue. (We do this for each return, in case the
// epilogue must be duplicated.)
if (MI.isReturn() || TII.isTailCall(MI)) {
FnSize += EpilogueSize;
}
// If the instruction is a call, and KCFI is enabled, then count the
// cost of a KCFI_CHECK_Thumb1 pseudo.
if (KCFI && MI.isCall() && MI.getCFIType()) {
const MCInstrDesc &MCID = TII.get(ARM::KCFI_CHECK_Thumb1);
FnSize += MCID.getSize();
}
if (MI.isUnconditionalBranch())
seenBranch = true;
}
// If there's no branch instruction in the block and we saw a constant,
// count a branch + realignment to 4 bytes, in case we have to branch round
// it.
if (seenConstantLoad && !seenBranch) {
FnSize += 4;
}
// Also, if the block is really, really big, then count an extra 4 bytes
// (again branch + realignment) for potentially splitting it in order to
// put constants in the middle, avoiding the problem of an LDR not being
// able to reach all the way to the end. The LDR offset limit is 1024
// bytes; the splitting itself adds some cost, but since any function this
// large is likely to have already gone over the "must stack LR" limit, we
// can keep things simple by assuming we split at half that rate.
unsigned BBSize = FnSize - SizeBeforeThisBB;
FnSize += 4 * BBSize / 512;
}
if (MF.getJumpTableInfo()) {
for (auto &Table : MF.getJumpTableInfo()->getJumpTables()) {
unsigned TableLen = Table.MBBs.size();
unsigned TableSizeBytes = TableLen * 4;
FnSize += TableSizeBytes;
}
}
LLVM_DEBUG(dbgs() << "Estimated function size for " << MF.getName() << " = "
<< FnSize << " bytes\n");
return FnSize;
}
/// estimateRSStackSizeLimit - Look at each instruction that references stack
/// frames and return the stack size limit beyond which some of these
/// instructions will require a scratch register during their expansion later.
// FIXME: Move to TII?
static unsigned estimateRSStackSizeLimit(MachineFunction &MF,
const TargetFrameLowering *TFI,
bool &HasNonSPFrameIndex) {
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
unsigned Limit = (1 << 12) - 1;
for (auto &MBB : MF) {
for (auto &MI : MBB) {
if (MI.isDebugInstr())
continue;
if (MI.getOpcode() == TargetOpcode::LOCAL_ESCAPE)
continue;
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
if (!MI.getOperand(i).isFI())
continue;
// When using ADDri to get the address of a stack object, 255 is the
// largest offset guaranteed to fit in the immediate offset.
if (MI.getOpcode() == ARM::ADDri) {
Limit = std::min(Limit, (1U << 8) - 1);
break;
}
// t2ADDri will not require an extra register, it can reuse the
// destination.
if (MI.getOpcode() == ARM::t2ADDri || MI.getOpcode() == ARM::t2ADDri12)
break;
const MCInstrDesc &MCID = MI.getDesc();
const TargetRegisterClass *RegClass = TII.getRegClass(MCID, i);
if (RegClass && !RegClass->contains(ARM::SP))
HasNonSPFrameIndex = true;
// Otherwise check the addressing mode.
switch (MI.getDesc().TSFlags & ARMII::AddrModeMask) {
case ARMII::AddrMode_i12:
case ARMII::AddrMode2:
// Default 12 bit limit.
break;
case ARMII::AddrMode3:
case ARMII::AddrModeT2_i8neg:
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode5FP16:
Limit = std::min(Limit, ((1U << 8) - 1) * 2);
break;
case ARMII::AddrMode5:
case ARMII::AddrModeT2_i8s4:
case ARMII::AddrModeT2_ldrex:
Limit = std::min(Limit, ((1U << 8) - 1) * 4);
break;
case ARMII::AddrModeT2_i12:
// i12 supports only positive offset so these will be converted to
// i8 opcodes. See llvm::rewriteT2FrameIndex.
if (TFI->hasFP(MF) && AFI->hasStackFrame())
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode4:
case ARMII::AddrMode6:
// Addressing modes 4 & 6 (load/store) instructions can't encode an
// immediate offset for stack references.
return 0;
case ARMII::AddrModeT2_i7:
Limit = std::min(Limit, ((1U << 7) - 1) * 1);
break;
case ARMII::AddrModeT2_i7s2:
Limit = std::min(Limit, ((1U << 7) - 1) * 2);
break;
case ARMII::AddrModeT2_i7s4:
Limit = std::min(Limit, ((1U << 7) - 1) * 4);
break;
default:
llvm_unreachable("Unhandled addressing mode in stack size limit calculation");
}
break; // At most one FI per instruction
}
}
}
return Limit;
}
// In functions that realign the stack, it can be an advantage to spill the
// callee-saved vector registers after realigning the stack. The vst1 and vld1
// instructions take alignment hints that can improve performance.
static void
checkNumAlignedDPRCS2Regs(MachineFunction &MF, BitVector &SavedRegs) {
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(0);
if (!SpillAlignedNEONRegs)
return;
// Naked functions don't spill callee-saved registers.
if (MF.getFunction().hasFnAttribute(Attribute::Naked))
return;
// We are planning to use NEON instructions vst1 / vld1.
if (!MF.getSubtarget<ARMSubtarget>().hasNEON())
return;
// Don't bother if the default stack alignment is sufficiently high.
if (MF.getSubtarget().getFrameLowering()->getStackAlign() >= Align(8))
return;
// Aligned spills require stack realignment.
if (!static_cast<const ARMBaseRegisterInfo *>(
MF.getSubtarget().getRegisterInfo())->canRealignStack(MF))
return;
// We always spill contiguous d-registers starting from d8. Count how many
// needs spilling. The register allocator will almost always use the
// callee-saved registers in order, but it can happen that there are holes in
// the range. Registers above the hole will be spilled to the standard DPRCS
// area.
unsigned NumSpills = 0;
for (; NumSpills < 8; ++NumSpills)
if (!SavedRegs.test(ARM::D8 + NumSpills))
break;
// Don't do this for just one d-register. It's not worth it.
if (NumSpills < 2)
return;
// Spill the first NumSpills D-registers after realigning the stack.
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(NumSpills);
// A scratch register is required for the vst1 / vld1 instructions.
SavedRegs.set(ARM::R4);
}
bool ARMFrameLowering::enableShrinkWrapping(const MachineFunction &MF) const {
// For CMSE entry functions, we want to save the FPCXT_NS immediately
// upon function entry (resp. restore it immediately before return)
if (STI.hasV8_1MMainlineOps() &&
MF.getInfo<ARMFunctionInfo>()->isCmseNSEntryFunction())
return false;
// We are disabling shrinkwrapping for now when PAC is enabled, as
// shrinkwrapping can cause clobbering of r12 when the PAC code is
// generated. A follow-up patch will fix this in a more performant manner.
if (MF.getInfo<ARMFunctionInfo>()->shouldSignReturnAddress(
true /* SpillsLR */))
return false;
return true;
}
bool ARMFrameLowering::requiresAAPCSFrameRecord(
const MachineFunction &MF) const {
const auto &Subtarget = MF.getSubtarget<ARMSubtarget>();
return Subtarget.createAAPCSFrameChain() && hasFP(MF);
}
// Thumb1 may require a spill when storing to a frame index through FP (or any
// access with execute-only), for cases where FP is a high register (R11). This
// scans the function for cases where this may happen.
static bool canSpillOnFrameIndexAccess(const MachineFunction &MF,
const TargetFrameLowering &TFI) {
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
if (!AFI->isThumb1OnlyFunction())
return false;
const ARMSubtarget &STI = MF.getSubtarget<ARMSubtarget>();
for (const auto &MBB : MF)
for (const auto &MI : MBB)
if (MI.getOpcode() == ARM::tSTRspi || MI.getOpcode() == ARM::tSTRi ||
STI.genExecuteOnly())
for (const auto &Op : MI.operands())
if (Op.isFI()) {
Register Reg;
TFI.getFrameIndexReference(MF, Op.getIndex(), Reg);
if (ARM::hGPRRegClass.contains(Reg) && Reg != ARM::SP)
return true;
}
return false;
}
void ARMFrameLowering::determineCalleeSaves(MachineFunction &MF,
BitVector &SavedRegs,
RegScavenger *RS) const {
TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
// This tells PEI to spill the FP as if it is any other callee-save register
// to take advantage the eliminateFrameIndex machinery. This also ensures it
// is spilled in the order specified by getCalleeSavedRegs() to make it easier
// to combine multiple loads / stores.
bool CanEliminateFrame = !(requiresAAPCSFrameRecord(MF) && hasFP(MF)) &&
!MF.disableFramePointerElim();
bool CS1Spilled = false;
bool LRSpilled = false;
unsigned NumGPRSpills = 0;
unsigned NumFPRSpills = 0;
SmallVector<unsigned, 4> UnspilledCS1GPRs;
SmallVector<unsigned, 4> UnspilledCS2GPRs;
const Function &F = MF.getFunction();
const ARMBaseRegisterInfo *RegInfo = static_cast<const ARMBaseRegisterInfo *>(
MF.getSubtarget().getRegisterInfo());
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
MachineFrameInfo &MFI = MF.getFrameInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
(void)TRI; // Silence unused warning in non-assert builds.
Register FramePtr = STI.getFramePointerReg();
ARMSubtarget::PushPopSplitVariation PushPopSplit =
STI.getPushPopSplitVariation(MF);
// For a floating point interrupt, save these registers always, since LLVM
// currently doesn't model reads/writes to these registers.
if (F.hasFnAttribute("interrupt") && F.hasFnAttribute("save-fp")) {
SavedRegs.set(ARM::FPSCR);
SavedRegs.set(ARM::R4);
// This register will only be present on non-MClass registers.
if (STI.isMClass()) {
SavedRegs.reset(ARM::FPEXC);
} else {
SavedRegs.set(ARM::FPEXC);
SavedRegs.set(ARM::R5);
}
}
// Spill R4 if Thumb2 function requires stack realignment - it will be used as
// scratch register. Also spill R4 if Thumb2 function has varsized objects,
// since it's not always possible to restore sp from fp in a single
// instruction.
// FIXME: It will be better just to find spare register here.
if (AFI->isThumb2Function() &&
(MFI.hasVarSizedObjects() || RegInfo->hasStackRealignment(MF)))
SavedRegs.set(ARM::R4);
// If a stack probe will be emitted, spill R4 and LR, since they are
// clobbered by the stack probe call.
// This estimate should be a safe, conservative estimate. The actual
// stack probe is enabled based on the size of the local objects;
// this estimate also includes the varargs store size.
if (STI.isTargetWindows() &&
WindowsRequiresStackProbe(MF, MFI.estimateStackSize(MF))) {
SavedRegs.set(ARM::R4);
SavedRegs.set(ARM::LR);
}
if (AFI->isThumb1OnlyFunction()) {
// Spill LR if Thumb1 function uses variable length argument lists.
if (AFI->getArgRegsSaveSize() > 0)
SavedRegs.set(ARM::LR);
// Spill R4 if Thumb1 epilogue has to restore SP from FP or the function
// requires stack alignment. We don't know for sure what the stack size
// will be, but for this, an estimate is good enough. If there anything
// changes it, it'll be a spill, which implies we've used all the registers
// and so R4 is already used, so not marking it here will be OK.
// FIXME: It will be better just to find spare register here.
if (MFI.hasVarSizedObjects() || RegInfo->hasStackRealignment(MF) ||
MFI.estimateStackSize(MF) > 508)
SavedRegs.set(ARM::R4);
}
// See if we can spill vector registers to aligned stack.
checkNumAlignedDPRCS2Regs(MF, SavedRegs);
// Spill the BasePtr if it's used.
if (RegInfo->hasBasePointer(MF))
SavedRegs.set(RegInfo->getBaseRegister());
// On v8.1-M.Main CMSE entry functions save/restore FPCXT.
if (STI.hasV8_1MMainlineOps() && AFI->isCmseNSEntryFunction())
CanEliminateFrame = false;
// When return address signing is enabled R12 is treated as callee-saved.
if (AFI->shouldSignReturnAddress())
CanEliminateFrame = false;
// Don't spill FP if the frame can be eliminated. This is determined
// by scanning the callee-save registers to see if any is modified.
const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF);
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
bool Spilled = false;
if (SavedRegs.test(Reg)) {
Spilled = true;
CanEliminateFrame = false;
}
if (!ARM::GPRRegClass.contains(Reg)) {
if (Spilled) {
if (ARM::SPRRegClass.contains(Reg))
NumFPRSpills++;
else if (ARM::DPRRegClass.contains(Reg))
NumFPRSpills += 2;
else if (ARM::QPRRegClass.contains(Reg))
NumFPRSpills += 4;
}
continue;
}
if (Spilled) {
NumGPRSpills++;
if (PushPopSplit != ARMSubtarget::SplitR7) {
if (Reg == ARM::LR)
LRSpilled = true;
CS1Spilled = true;
continue;
}
// Keep track if LR and any of R4, R5, R6, and R7 is spilled.
switch (Reg) {
case ARM::LR:
LRSpilled = true;
[[fallthrough]];
case ARM::R0: case ARM::R1:
case ARM::R2: case ARM::R3:
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
CS1Spilled = true;
break;
default:
break;
}
} else {
if (PushPopSplit != ARMSubtarget::SplitR7) {
UnspilledCS1GPRs.push_back(Reg);
continue;
}
switch (Reg) {
case ARM::R0: case ARM::R1:
case ARM::R2: case ARM::R3:
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
case ARM::LR:
UnspilledCS1GPRs.push_back(Reg);
break;
default:
UnspilledCS2GPRs.push_back(Reg);
break;
}
}
}
bool ForceLRSpill = false;
// If any of the stack slot references may be out of range of an immediate
// offset, make sure a register (or a spill slot) is available for the
// register scavenger. Note that if we're indexing off the frame pointer, the
// effective stack size is 4 bytes larger since the FP points to the stack
// slot of the previous FP. Also, if we have variable sized objects in the
// function, stack slot references will often be negative, and some of
// our instructions are positive-offset only, so conservatively consider
// that case to want a spill slot (or register) as well. Similarly, if
// the function adjusts the stack pointer during execution and the
// adjustments aren't already part of our stack size estimate, our offset
// calculations may be off, so be conservative.
// FIXME: We could add logic to be more precise about negative offsets
// and which instructions will need a scratch register for them. Is it
// worth the effort and added fragility?
unsigned EstimatedStackSize =
MFI.estimateStackSize(MF) + 4 * (NumGPRSpills + NumFPRSpills);
// Determine biggest (positive) SP offset in MachineFrameInfo.
int MaxFixedOffset = 0;
for (int I = MFI.getObjectIndexBegin(); I < 0; ++I) {
int MaxObjectOffset = MFI.getObjectOffset(I) + MFI.getObjectSize(I);
MaxFixedOffset = std::max(MaxFixedOffset, MaxObjectOffset);
}
bool HasFP = hasFP(MF);
if (HasFP) {
if (AFI->hasStackFrame())
EstimatedStackSize += 4;
} else {
// If FP is not used, SP will be used to access arguments, so count the
// size of arguments into the estimation.
EstimatedStackSize += MaxFixedOffset;
}
EstimatedStackSize += 16; // For possible paddings.
unsigned EstimatedRSStackSizeLimit, EstimatedRSFixedSizeLimit;
bool HasNonSPFrameIndex = false;
if (AFI->isThumb1OnlyFunction()) {
// For Thumb1, don't bother to iterate over the function. The only
// instruction that requires an emergency spill slot is a store to a
// frame index.
//
// tSTRspi, which is used for sp-relative accesses, has an 8-bit unsigned
// immediate. tSTRi, which is used for bp- and fp-relative accesses, has
// a 5-bit unsigned immediate.
//
// We could try to check if the function actually contains a tSTRspi
// that might need the spill slot, but it's not really important.
// Functions with VLAs or extremely large call frames are rare, and
// if a function is allocating more than 1KB of stack, an extra 4-byte
// slot probably isn't relevant.
//
// A special case is the scenario where r11 is used as FP, where accesses
// to a frame index will require its value to be moved into a low reg.
// This is handled later on, once we are able to determine if we have any
// fp-relative accesses.
if (RegInfo->hasBasePointer(MF))
EstimatedRSStackSizeLimit = (1U << 5) * 4;
else
EstimatedRSStackSizeLimit = (1U << 8) * 4;
EstimatedRSFixedSizeLimit = (1U << 5) * 4;
} else {
EstimatedRSStackSizeLimit =
estimateRSStackSizeLimit(MF, this, HasNonSPFrameIndex);
EstimatedRSFixedSizeLimit = EstimatedRSStackSizeLimit;
}
// Final estimate of whether sp or bp-relative accesses might require
// scavenging.
bool HasLargeStack = EstimatedStackSize > EstimatedRSStackSizeLimit;
// If the stack pointer moves and we don't have a base pointer, the
// estimate logic doesn't work. The actual offsets might be larger when
// we're constructing a call frame, or we might need to use negative
// offsets from fp.
bool HasMovingSP = MFI.hasVarSizedObjects() ||
(MFI.adjustsStack() && !canSimplifyCallFramePseudos(MF));
bool HasBPOrFixedSP = RegInfo->hasBasePointer(MF) || !HasMovingSP;
// If we have a frame pointer, we assume arguments will be accessed
// relative to the frame pointer. Check whether fp-relative accesses to
// arguments require scavenging.
//
// We could do slightly better on Thumb1; in some cases, an sp-relative
// offset would be legal even though an fp-relative offset is not.
int MaxFPOffset = getMaxFPOffset(STI, *AFI, MF);
bool HasLargeArgumentList =
HasFP && (MaxFixedOffset - MaxFPOffset) > (int)EstimatedRSFixedSizeLimit;
bool BigFrameOffsets = HasLargeStack || !HasBPOrFixedSP ||
HasLargeArgumentList || HasNonSPFrameIndex;
LLVM_DEBUG(dbgs() << "EstimatedLimit: " << EstimatedRSStackSizeLimit
<< "; EstimatedStack: " << EstimatedStackSize
<< "; EstimatedFPStack: " << MaxFixedOffset - MaxFPOffset
<< "; BigFrameOffsets: " << BigFrameOffsets << "\n");
if (!LRSpilled && AFI->isThumb1OnlyFunction()) {
unsigned FnSize = EstimateFunctionSizeInBytes(MF, TII, STI, RegInfo,
SavedRegs, BigFrameOffsets);
if (FnSize >= (1 << 11)) {
// Force LR to be spilled if the Thumb function size is > 2048. This
// enables use of BL to implement far jump.
CanEliminateFrame = false;
ForceLRSpill = true;
}
}
if (BigFrameOffsets ||
!CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) {
AFI->setHasStackFrame(true);
// Save the FP if:
// 1. We currently need it (HasFP), OR
// 2. We might need it later due to stack realignment from aligned DPRCS2
// saves (which will make hasFP() become true in emitPrologue).
if (HasFP || (isFPReserved(MF) && AFI->getNumAlignedDPRCS2Regs() > 0)) {
SavedRegs.set(FramePtr);
// If the frame pointer is required by the ABI, also spill LR so that we
// emit a complete frame record.
if ((requiresAAPCSFrameRecord(MF) || MF.disableFramePointerElim()) &&
!LRSpilled) {
SavedRegs.set(ARM::LR);
LRSpilled = true;
NumGPRSpills++;
auto LRPos = llvm::find(UnspilledCS1GPRs, ARM::LR);
if (LRPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(LRPos);
}
auto FPPos = llvm::find(UnspilledCS1GPRs, FramePtr);
if (FPPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(FPPos);
NumGPRSpills++;
if (FramePtr == ARM::R7)
CS1Spilled = true;
}
// This is the number of extra spills inserted for callee-save GPRs which
// would not otherwise be used by the function. When greater than zero it
// guaranteees that it is possible to scavenge a register to hold the
// address of a stack slot. On Thumb1, the register must be a valid operand
// to tSTRi, i.e. r4-r7. For other subtargets, this is any GPR, i.e. r4-r11
// or lr.
//
// If we don't insert a spill, we instead allocate an emergency spill
// slot, which can be used by scavenging to spill an arbitrary register.
//
// We currently don't try to figure out whether any specific instruction
// requires scavening an additional register.
unsigned NumExtraCSSpill = 0;
if (AFI->isThumb1OnlyFunction()) {
// For Thumb1-only targets, we need some low registers when we save and
// restore the high registers (which aren't allocatable, but could be
// used by inline assembly) because the push/pop instructions can not
// access high registers. If necessary, we might need to push more low
// registers to ensure that there is at least one free that can be used
// for the saving & restoring, and preferably we should ensure that as
// many as are needed are available so that fewer push/pop instructions
// are required.
// Low registers which are not currently pushed, but could be (r4-r7).
SmallVector<unsigned, 4> AvailableRegs;
// Unused argument registers (r0-r3) can be clobbered in the prologue for
// free.
int EntryRegDeficit = 0;
for (unsigned Reg : {ARM::R0, ARM::R1, ARM::R2, ARM::R3}) {
if (!MF.getRegInfo().isLiveIn(Reg)) {
--EntryRegDeficit;
LLVM_DEBUG(dbgs()
<< printReg(Reg, TRI)
<< " is unused argument register, EntryRegDeficit = "
<< EntryRegDeficit << "\n");
}
}
// Unused return registers can be clobbered in the epilogue for free.
int ExitRegDeficit = AFI->getReturnRegsCount() - 4;
LLVM_DEBUG(dbgs() << AFI->getReturnRegsCount()
<< " return regs used, ExitRegDeficit = "
<< ExitRegDeficit << "\n");
int RegDeficit = std::max(EntryRegDeficit, ExitRegDeficit);
LLVM_DEBUG(dbgs() << "RegDeficit = " << RegDeficit << "\n");
// r4-r6 can be used in the prologue if they are pushed by the first push
// instruction.
for (unsigned Reg : {ARM::R4, ARM::R5, ARM::R6}) {
if (SavedRegs.test(Reg)) {
--RegDeficit;
LLVM_DEBUG(dbgs() << printReg(Reg, TRI)
<< " is saved low register, RegDeficit = "
<< RegDeficit << "\n");
} else {
AvailableRegs.push_back(Reg);
LLVM_DEBUG(
dbgs()
<< printReg(Reg, TRI)
<< " is non-saved low register, adding to AvailableRegs\n");
}
}
// r7 can be used if it is not being used as the frame pointer.
if (!HasFP || FramePtr != ARM::R7) {
if (SavedRegs.test(ARM::R7)) {
--RegDeficit;
LLVM_DEBUG(dbgs() << "%r7 is saved low register, RegDeficit = "
<< RegDeficit << "\n");
} else {
AvailableRegs.push_back(ARM::R7);
LLVM_DEBUG(
dbgs()
<< "%r7 is non-saved low register, adding to AvailableRegs\n");
}
}
// Each of r8-r11 needs to be copied to a low register, then pushed.
for (unsigned Reg : {ARM::R8, ARM::R9, ARM::R10, ARM::R11}) {
if (SavedRegs.test(Reg)) {
++RegDeficit;
LLVM_DEBUG(dbgs() << printReg(Reg, TRI)
<< " is saved high register, RegDeficit = "
<< RegDeficit << "\n");
}
}
// LR can only be used by PUSH, not POP, and can't be used at all if the
// llvm.returnaddress intrinsic is used. This is only worth doing if we
// are more limited at function entry than exit.
if ((EntryRegDeficit > ExitRegDeficit) &&
!(MF.getRegInfo().isLiveIn(ARM::LR) &&
MF.getFrameInfo().isReturnAddressTaken())) {
if (SavedRegs.test(ARM::LR)) {
--RegDeficit;
LLVM_DEBUG(dbgs() << "%lr is saved register, RegDeficit = "
<< RegDeficit << "\n");
} else {
AvailableRegs.push_back(ARM::LR);
LLVM_DEBUG(dbgs() << "%lr is not saved, adding to AvailableRegs\n");
}
}
// If there are more high registers that need pushing than low registers
// available, push some more low registers so that we can use fewer push
// instructions. This might not reduce RegDeficit all the way to zero,
// because we can only guarantee that r4-r6 are available, but r8-r11 may
// need saving.
LLVM_DEBUG(dbgs() << "Final RegDeficit = " << RegDeficit << "\n");
for (; RegDeficit > 0 && !AvailableRegs.empty(); --RegDeficit) {
unsigned Reg = AvailableRegs.pop_back_val();
LLVM_DEBUG(dbgs() << "Spilling " << printReg(Reg, TRI)
<< " to make up reg deficit\n");
SavedRegs.set(Reg);
NumGPRSpills++;
CS1Spilled = true;
assert(!MRI.isReserved(Reg) && "Should not be reserved");
if (Reg != ARM::LR && !MRI.isPhysRegUsed(Reg))
NumExtraCSSpill++;
UnspilledCS1GPRs.erase(llvm::find(UnspilledCS1GPRs, Reg));
if (Reg == ARM::LR)
LRSpilled = true;
}
LLVM_DEBUG(dbgs() << "After adding spills, RegDeficit = " << RegDeficit
<< "\n");
}
// Avoid spilling LR in Thumb1 if there's a tail call: it's expensive to
// restore LR in that case.
bool ExpensiveLRRestore = AFI->isThumb1OnlyFunction() && MFI.hasTailCall();
// If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
// Spill LR as well so we can fold BX_RET to the registers restore (LDM).
if (!LRSpilled && CS1Spilled && !ExpensiveLRRestore) {
SavedRegs.set(ARM::LR);
NumGPRSpills++;
SmallVectorImpl<unsigned>::iterator LRPos;
LRPos = llvm::find(UnspilledCS1GPRs, (unsigned)ARM::LR);
if (LRPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(LRPos);
ForceLRSpill = false;
if (!MRI.isReserved(ARM::LR) && !MRI.isPhysRegUsed(ARM::LR) &&
!AFI->isThumb1OnlyFunction())
NumExtraCSSpill++;
}
// If stack and double are 8-byte aligned and we are spilling an odd number
// of GPRs, spill one extra callee save GPR so we won't have to pad between
// the integer and double callee save areas.
LLVM_DEBUG(dbgs() << "NumGPRSpills = " << NumGPRSpills << "\n");
const Align TargetAlign = getStackAlign();
if (TargetAlign >= Align(8) && (NumGPRSpills & 1)) {
if (CS1Spilled && !UnspilledCS1GPRs.empty()) {
for (unsigned Reg : UnspilledCS1GPRs) {
// Don't spill high register if the function is thumb. In the case of
// Windows on ARM, accept R11 (frame pointer)
if (!AFI->isThumbFunction() ||
(STI.isTargetWindows() && Reg == ARM::R11) ||
isARMLowRegister(Reg) ||
(Reg == ARM::LR && !ExpensiveLRRestore)) {
SavedRegs.set(Reg);
LLVM_DEBUG(dbgs() << "Spilling " << printReg(Reg, TRI)
<< " to make up alignment\n");
if (!MRI.isReserved(Reg) && !MRI.isPhysRegUsed(Reg) &&
!(Reg == ARM::LR && AFI->isThumb1OnlyFunction()))
NumExtraCSSpill++;
break;
}
}
} else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) {
unsigned Reg = UnspilledCS2GPRs.front();
SavedRegs.set(Reg);
LLVM_DEBUG(dbgs() << "Spilling " << printReg(Reg, TRI)
<< " to make up alignment\n");
if (!MRI.isReserved(Reg) && !MRI.isPhysRegUsed(Reg))
NumExtraCSSpill++;
}
}
// Estimate if we might need to scavenge registers at some point in order
// to materialize a stack offset. If so, either spill one additional
// callee-saved register or reserve a special spill slot to facilitate
// register scavenging. Thumb1 needs a spill slot for stack pointer
// adjustments and for frame index accesses when FP is high register,
// even when the frame itself is small.
unsigned RegsNeeded = 0;
if (BigFrameOffsets || canSpillOnFrameIndexAccess(MF, *this)) {
RegsNeeded++;
// With thumb1 execute-only we may need an additional register for saving
// and restoring the CPSR.
if (AFI->isThumb1OnlyFunction() && STI.genExecuteOnly() && !STI.useMovt())
RegsNeeded++;
}
if (RegsNeeded > NumExtraCSSpill) {
// If any non-reserved CS register isn't spilled, just spill one or two
// extra. That should take care of it!
unsigned NumExtras = TargetAlign.value() / 4;
SmallVector<unsigned, 2> Extras;
while (NumExtras && !UnspilledCS1GPRs.empty()) {
unsigned Reg = UnspilledCS1GPRs.pop_back_val();
if (!MRI.isReserved(Reg) &&
(!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg))) {
Extras.push_back(Reg);
NumExtras--;
}
}
// For non-Thumb1 functions, also check for hi-reg CS registers
if (!AFI->isThumb1OnlyFunction()) {
while (NumExtras && !UnspilledCS2GPRs.empty()) {
unsigned Reg = UnspilledCS2GPRs.pop_back_val();
if (!MRI.isReserved(Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
}
if (NumExtras == 0) {
for (unsigned Reg : Extras) {
SavedRegs.set(Reg);
if (!MRI.isPhysRegUsed(Reg))
NumExtraCSSpill++;
}
}
while ((RegsNeeded > NumExtraCSSpill) && RS) {
// Reserve a slot closest to SP or frame pointer.
LLVM_DEBUG(dbgs() << "Reserving emergency spill slot\n");
const TargetRegisterClass &RC = ARM::GPRRegClass;
unsigned Size = TRI->getSpillSize(RC);
Align Alignment = TRI->getSpillAlign(RC);
RS->addScavengingFrameIndex(
MFI.CreateSpillStackObject(Size, Alignment));
--RegsNeeded;
}
}
}
if (ForceLRSpill)
SavedRegs.set(ARM::LR);
AFI->setLRIsSpilled(SavedRegs.test(ARM::LR));
}
void ARMFrameLowering::updateLRRestored(MachineFunction &MF) {
MachineFrameInfo &MFI = MF.getFrameInfo();
if (!MFI.isCalleeSavedInfoValid())
return;
// Check if all terminators do not implicitly use LR. Then we can 'restore' LR
// into PC so it is not live out of the return block: Clear the Restored bit
// in that case.
for (CalleeSavedInfo &Info : MFI.getCalleeSavedInfo()) {
if (Info.getReg() != ARM::LR)
continue;
if (all_of(MF, [](const MachineBasicBlock &MBB) {
return all_of(MBB.terminators(), [](const MachineInstr &Term) {
return !Term.isReturn() || Term.getOpcode() == ARM::LDMIA_RET ||
Term.getOpcode() == ARM::t2LDMIA_RET ||
Term.getOpcode() == ARM::tPOP_RET;
});
})) {
Info.setRestored(false);
break;
}
}
}
void ARMFrameLowering::processFunctionBeforeFrameFinalized(
MachineFunction &MF, RegScavenger *RS) const {
TargetFrameLowering::processFunctionBeforeFrameFinalized(MF, RS);
updateLRRestored(MF);
}
void ARMFrameLowering::getCalleeSaves(const MachineFunction &MF,
BitVector &SavedRegs) const {
TargetFrameLowering::getCalleeSaves(MF, SavedRegs);
// If we have the "returned" parameter attribute which guarantees that we
// return the value which was passed in r0 unmodified (e.g. C++ 'structors),
// record that fact for IPRA.
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
if (AFI->getPreservesR0())
SavedRegs.set(ARM::R0);
}
bool ARMFrameLowering::assignCalleeSavedSpillSlots(
MachineFunction &MF, const TargetRegisterInfo *TRI,
std::vector<CalleeSavedInfo> &CSI) const {
// For CMSE entry functions, handle floating-point context as if it was a
// callee-saved register.
if (STI.hasV8_1MMainlineOps() &&
MF.getInfo<ARMFunctionInfo>()->isCmseNSEntryFunction()) {
CSI.emplace_back(ARM::FPCXTNS);
CSI.back().setRestored(false);
}
// For functions, which sign their return address, upon function entry, the
// return address PAC is computed in R12. Treat R12 as a callee-saved register
// in this case.
const auto &AFI = *MF.getInfo<ARMFunctionInfo>();
if (AFI.shouldSignReturnAddress()) {
// The order of register must match the order we push them, because the
// PEI assigns frame indices in that order. That order depends on the
// PushPopSplitVariation, there are only two cases which we use with return
// address signing:
switch (STI.getPushPopSplitVariation(MF)) {
case ARMSubtarget::SplitR7:
// LR, R7, R6, R5, R4, <R12>, R11, R10, R9, R8, D15-D8
CSI.insert(find_if(CSI,
[=](const auto &CS) {
MCRegister Reg = CS.getReg();
return Reg == ARM::R10 || Reg == ARM::R11 ||
Reg == ARM::R8 || Reg == ARM::R9 ||
ARM::DPRRegClass.contains(Reg);
}),
CalleeSavedInfo(ARM::R12));
break;
case ARMSubtarget::SplitR11AAPCSSignRA:
// With SplitR11AAPCSSignRA, R12 will always be the highest-addressed CSR
// on the stack.
CSI.insert(CSI.begin(), CalleeSavedInfo(ARM::R12));
break;
case ARMSubtarget::NoSplit:
assert(!MF.disableFramePointerElim() &&
"ABI-required frame pointers need a CSR split when signing return "
"address.");
CSI.insert(find_if(CSI,
[=](const auto &CS) {
MCRegister Reg = CS.getReg();
return Reg != ARM::LR;
}),
CalleeSavedInfo(ARM::R12));
break;
default:
llvm_unreachable("Unexpected CSR split with return address signing");
}
}
return false;
}
const TargetFrameLowering::SpillSlot *
ARMFrameLowering::getCalleeSavedSpillSlots(unsigned &NumEntries) const {
static const SpillSlot FixedSpillOffsets[] = {{ARM::FPCXTNS, -4}};
NumEntries = std::size(FixedSpillOffsets);
return FixedSpillOffsets;
}
MachineBasicBlock::iterator ARMFrameLowering::eliminateCallFramePseudoInstr(
MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
bool isARM = !AFI->isThumbFunction();
DebugLoc dl = I->getDebugLoc();
unsigned Opc = I->getOpcode();
bool IsDestroy = Opc == TII.getCallFrameDestroyOpcode();
unsigned CalleePopAmount = IsDestroy ? I->getOperand(1).getImm() : 0;
assert(!AFI->isThumb1OnlyFunction() &&
"This eliminateCallFramePseudoInstr does not support Thumb1!");
int PIdx = I->findFirstPredOperandIdx();
ARMCC::CondCodes Pred = (PIdx == -1)
? ARMCC::AL
: (ARMCC::CondCodes)I->getOperand(PIdx).getImm();
unsigned PredReg = TII.getFramePred(*I);
if (!hasReservedCallFrame(MF)) {
// Bail early if the callee is expected to do the adjustment.
if (IsDestroy && CalleePopAmount != -1U)
return MBB.erase(I);
// If we have alloca, convert as follows:
// ADJCALLSTACKDOWN -> sub, sp, sp, amount
// ADJCALLSTACKUP -> add, sp, sp, amount
unsigned Amount = TII.getFrameSize(*I);
if (Amount != 0) {
// We need to keep the stack aligned properly. To do this, we round the
// amount of space needed for the outgoing arguments up to the next
// alignment boundary.
Amount = alignSPAdjust(Amount);
if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) {
emitSPUpdate(isARM, MBB, I, dl, TII, -Amount, MachineInstr::NoFlags,
Pred, PredReg);
} else {
assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP);
emitSPUpdate(isARM, MBB, I, dl, TII, Amount, MachineInstr::NoFlags,
Pred, PredReg);
}
}
} else if (CalleePopAmount != -1U) {
// If the calling convention demands that the callee pops arguments from the
// stack, we want to add it back if we have a reserved call frame.
emitSPUpdate(isARM, MBB, I, dl, TII, -CalleePopAmount,
MachineInstr::NoFlags, Pred, PredReg);
}
return MBB.erase(I);
}
/// Get the minimum constant for ARM that is greater than or equal to the
/// argument. In ARM, constants can have any value that can be produced by
/// rotating an 8-bit value to the right by an even number of bits within a
/// 32-bit word.
static uint32_t alignToARMConstant(uint32_t Value) {
unsigned Shifted = 0;
if (Value == 0)
return 0;
while (!(Value & 0xC0000000)) {
Value = Value << 2;
Shifted += 2;
}
bool Carry = (Value & 0x00FFFFFF);
Value = ((Value & 0xFF000000) >> 24) + Carry;
if (Value & 0x0000100)
Value = Value & 0x000001FC;
if (Shifted > 24)
Value = Value >> (Shifted - 24);
else
Value = Value << (24 - Shifted);
return Value;
}
// The stack limit in the TCB is set to this many bytes above the actual
// stack limit.
static const uint64_t kSplitStackAvailable = 256;
// Adjust the function prologue to enable split stacks. This currently only
// supports android and linux.
//
// The ABI of the segmented stack prologue is a little arbitrarily chosen, but
// must be well defined in order to allow for consistent implementations of the
// __morestack helper function. The ABI is also not a normal ABI in that it
// doesn't follow the normal calling conventions because this allows the
// prologue of each function to be optimized further.
//
// Currently, the ABI looks like (when calling __morestack)
//
// * r4 holds the minimum stack size requested for this function call
// * r5 holds the stack size of the arguments to the function
// * the beginning of the function is 3 instructions after the call to
// __morestack
//
// Implementations of __morestack should use r4 to allocate a new stack, r5 to
// place the arguments on to the new stack, and the 3-instruction knowledge to
// jump directly to the body of the function when working on the new stack.
//
// An old (and possibly no longer compatible) implementation of __morestack for
// ARM can be found at [1].
//
// [1] - https://github.com/mozilla/rust/blob/86efd9/src/rt/arch/arm/morestack.S
void ARMFrameLowering::adjustForSegmentedStacks(
MachineFunction &MF, MachineBasicBlock &PrologueMBB) const {
unsigned Opcode;
const ARMSubtarget *ST = &MF.getSubtarget<ARMSubtarget>();
bool Thumb = ST->isThumb();
bool Thumb2 = ST->isThumb2();
// Sadly, this currently doesn't support varargs, platforms other than
// android/linux. Note that thumb1/thumb2 are support for android/linux.
if (MF.getFunction().isVarArg())
report_fatal_error("Segmented stacks do not support vararg functions.");
if (!ST->isTargetAndroid() && !ST->isTargetLinux())
report_fatal_error("Segmented stacks not supported on this platform.");
MachineFrameInfo &MFI = MF.getFrameInfo();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo *>(MF.getSubtarget().getInstrInfo());
ARMFunctionInfo *ARMFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL;
if (!MFI.needsSplitStackProlog())
return;
uint64_t StackSize = MFI.getStackSize();
// Use R4 and R5 as scratch registers.
// We save R4 and R5 before use and restore them before leaving the function.
unsigned ScratchReg0 = ARM::R4;
unsigned ScratchReg1 = ARM::R5;
unsigned MovOp = ST->useMovt() ? ARM::t2MOVi32imm : ARM::tMOVi32imm;
uint64_t AlignedStackSize;
MachineBasicBlock *PrevStackMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *PostStackMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *AllocMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *GetMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *McrMBB = MF.CreateMachineBasicBlock();
// Grab everything that reaches PrologueMBB to update there liveness as well.
SmallPtrSet<MachineBasicBlock *, 8> BeforePrologueRegion;
SmallVector<MachineBasicBlock *, 2> WalkList;
WalkList.push_back(&PrologueMBB);
do {
MachineBasicBlock *CurMBB = WalkList.pop_back_val();
for (MachineBasicBlock *PredBB : CurMBB->predecessors()) {
if (BeforePrologueRegion.insert(PredBB).second)
WalkList.push_back(PredBB);
}
} while (!WalkList.empty());
// The order in that list is important.
// The blocks will all be inserted before PrologueMBB using that order.
// Therefore the block that should appear first in the CFG should appear
// first in the list.
MachineBasicBlock *AddedBlocks[] = {PrevStackMBB, McrMBB, GetMBB, AllocMBB,
PostStackMBB};
BeforePrologueRegion.insert_range(AddedBlocks);
for (const auto &LI : PrologueMBB.liveins()) {
for (MachineBasicBlock *PredBB : BeforePrologueRegion)
PredBB->addLiveIn(LI);
}
// Remove the newly added blocks from the list, since we know
// we do not have to do the following updates for them.
for (MachineBasicBlock *B : AddedBlocks) {
BeforePrologueRegion.erase(B);
MF.insert(PrologueMBB.getIterator(), B);
}
for (MachineBasicBlock *MBB : BeforePrologueRegion) {
// Make sure the LiveIns are still sorted and unique.
MBB->sortUniqueLiveIns();
// Replace the edges to PrologueMBB by edges to the sequences
// we are about to add, but only update for immediate predecessors.
if (MBB->isSuccessor(&PrologueMBB))
MBB->ReplaceUsesOfBlockWith(&PrologueMBB, AddedBlocks[0]);
}
// The required stack size that is aligned to ARM constant criterion.
AlignedStackSize = alignToARMConstant(StackSize);
// When the frame size is less than 256 we just compare the stack
// boundary directly to the value of the stack pointer, per gcc.
bool CompareStackPointer = AlignedStackSize < kSplitStackAvailable;
// We will use two of the callee save registers as scratch registers so we
// need to save those registers onto the stack.
// We will use SR0 to hold stack limit and SR1 to hold the stack size
// requested and arguments for __morestack().
// SR0: Scratch Register #0
// SR1: Scratch Register #1
// push {SR0, SR1}
if (Thumb) {
BuildMI(PrevStackMBB, DL, TII.get(ARM::tPUSH))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
BuildMI(PrevStackMBB, DL, TII.get(ARM::STMDB_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Emit the relevant DWARF information about the change in stack pointer as
// well as where to find both r4 and r5 (the callee-save registers)
if (!MF.getTarget().getMCAsmInfo().usesWindowsCFI()) {
CFIInstBuilder CFIBuilder(PrevStackMBB, MachineInstr::NoFlags);
CFIBuilder.buildDefCFAOffset(8);
CFIBuilder.buildOffset(ScratchReg1, -4);
CFIBuilder.buildOffset(ScratchReg0, -8);
}
// mov SR1, sp
if (Thumb) {
BuildMI(McrMBB, DL, TII.get(ARM::tMOVr), ScratchReg1)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL));
} else if (CompareStackPointer) {
BuildMI(McrMBB, DL, TII.get(ARM::MOVr), ScratchReg1)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
// sub SR1, sp, #StackSize
if (!CompareStackPointer && Thumb) {
if (AlignedStackSize < 256) {
BuildMI(McrMBB, DL, TII.get(ARM::tSUBi8), ScratchReg1)
.add(condCodeOp())
.addReg(ScratchReg1)
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL));
} else {
if (Thumb2 || ST->genExecuteOnly()) {
BuildMI(McrMBB, DL, TII.get(MovOp), ScratchReg0)
.addImm(AlignedStackSize);
} else {
auto MBBI = McrMBB->end();
auto RegInfo = STI.getRegisterInfo();
RegInfo->emitLoadConstPool(*McrMBB, MBBI, DL, ScratchReg0, 0,
AlignedStackSize);
}
BuildMI(McrMBB, DL, TII.get(ARM::tSUBrr), ScratchReg1)
.add(condCodeOp())
.addReg(ScratchReg1)
.addReg(ScratchReg0)
.add(predOps(ARMCC::AL));
}
} else if (!CompareStackPointer) {
if (AlignedStackSize < 256) {
BuildMI(McrMBB, DL, TII.get(ARM::SUBri), ScratchReg1)
.addReg(ARM::SP)
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
} else {
auto MBBI = McrMBB->end();
auto RegInfo = STI.getRegisterInfo();
RegInfo->emitLoadConstPool(*McrMBB, MBBI, DL, ScratchReg0, 0,
AlignedStackSize);
BuildMI(McrMBB, DL, TII.get(ARM::SUBrr), ScratchReg1)
.addReg(ARM::SP)
.addReg(ScratchReg0)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
}
}
if (Thumb && ST->isThumb1Only()) {
if (ST->genExecuteOnly()) {
BuildMI(GetMBB, DL, TII.get(MovOp), ScratchReg0)
.addExternalSymbol("__STACK_LIMIT");
} else {
unsigned PCLabelId = ARMFI->createPICLabelUId();
ARMConstantPoolValue *NewCPV = ARMConstantPoolSymbol::Create(
MF.getFunction().getContext(), "__STACK_LIMIT", PCLabelId, 0);
MachineConstantPool *MCP = MF.getConstantPool();
unsigned CPI = MCP->getConstantPoolIndex(NewCPV, Align(4));
// ldr SR0, [pc, offset(STACK_LIMIT)]
BuildMI(GetMBB, DL, TII.get(ARM::tLDRpci), ScratchReg0)
.addConstantPoolIndex(CPI)
.add(predOps(ARMCC::AL));
}
// ldr SR0, [SR0]
BuildMI(GetMBB, DL, TII.get(ARM::tLDRi), ScratchReg0)
.addReg(ScratchReg0)
.addImm(0)
.add(predOps(ARMCC::AL));
} else {
// Get TLS base address from the coprocessor
// mrc p15, #0, SR0, c13, c0, #3
BuildMI(McrMBB, DL, TII.get(Thumb ? ARM::t2MRC : ARM::MRC),
ScratchReg0)
.addImm(15)
.addImm(0)
.addImm(13)
.addImm(0)
.addImm(3)
.add(predOps(ARMCC::AL));
// Use the last tls slot on android and a private field of the TCP on linux.
assert(ST->isTargetAndroid() || ST->isTargetLinux());
unsigned TlsOffset = ST->isTargetAndroid() ? 63 : 1;
// Get the stack limit from the right offset
// ldr SR0, [sr0, #4 * TlsOffset]
BuildMI(GetMBB, DL, TII.get(Thumb ? ARM::t2LDRi12 : ARM::LDRi12),
ScratchReg0)
.addReg(ScratchReg0)
.addImm(4 * TlsOffset)
.add(predOps(ARMCC::AL));
}
// Compare stack limit with stack size requested.
// cmp SR0, SR1
Opcode = Thumb ? ARM::tCMPr : ARM::CMPrr;
BuildMI(GetMBB, DL, TII.get(Opcode))
.addReg(ScratchReg0)
.addReg(ScratchReg1)
.add(predOps(ARMCC::AL));
// This jump is taken if StackLimit <= SP - stack required.
Opcode = Thumb ? ARM::tBcc : ARM::Bcc;
BuildMI(GetMBB, DL, TII.get(Opcode))
.addMBB(PostStackMBB)
.addImm(ARMCC::LS)
.addReg(ARM::CPSR);
// Calling __morestack(StackSize, Size of stack arguments).
// __morestack knows that the stack size requested is in SR0(r4)
// and amount size of stack arguments is in SR1(r5).
// Pass first argument for the __morestack by Scratch Register #0.
// The amount size of stack required
if (Thumb) {
if (AlignedStackSize < 256) {
BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8), ScratchReg0)
.add(condCodeOp())
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL));
} else {
if (Thumb2 || ST->genExecuteOnly()) {
BuildMI(AllocMBB, DL, TII.get(MovOp), ScratchReg0)
.addImm(AlignedStackSize);
} else {
auto MBBI = AllocMBB->end();
auto RegInfo = STI.getRegisterInfo();
RegInfo->emitLoadConstPool(*AllocMBB, MBBI, DL, ScratchReg0, 0,
AlignedStackSize);
}
}
} else {
if (AlignedStackSize < 256) {
BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg0)
.addImm(AlignedStackSize)
.add(predOps(ARMCC::AL))
.add(condCodeOp());
} else {
auto MBBI = AllocMBB->end();
auto RegInfo = STI.getRegisterInfo();
RegInfo->emitLoadConstPool(*AllocMBB, MBBI, DL, ScratchReg0, 0,
AlignedStackSize);
}
}
// Pass second argument for the __morestack by Scratch Register #1.
// The amount size of stack consumed to save function arguments.
if (Thumb) {
if (ARMFI->getArgumentStackSize() < 256) {
BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8), ScratchReg1)
.add(condCodeOp())
.addImm(alignToARMConstant(ARMFI->getArgumentStackSize()))
.add(predOps(ARMCC::AL));
} else {
if (Thumb2 || ST->genExecuteOnly()) {
BuildMI(AllocMBB, DL, TII.get(MovOp), ScratchReg1)
.addImm(alignToARMConstant(ARMFI->getArgumentStackSize()));
} else {
auto MBBI = AllocMBB->end();
auto RegInfo = STI.getRegisterInfo();
RegInfo->emitLoadConstPool(
*AllocMBB, MBBI, DL, ScratchReg1, 0,
alignToARMConstant(ARMFI->getArgumentStackSize()));
}
}
} else {
if (alignToARMConstant(ARMFI->getArgumentStackSize()) < 256) {
BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg1)
.addImm(alignToARMConstant(ARMFI->getArgumentStackSize()))
.add(predOps(ARMCC::AL))
.add(condCodeOp());
} else {
auto MBBI = AllocMBB->end();
auto RegInfo = STI.getRegisterInfo();
RegInfo->emitLoadConstPool(
*AllocMBB, MBBI, DL, ScratchReg1, 0,
alignToARMConstant(ARMFI->getArgumentStackSize()));
}
}
// push {lr} - Save return address of this function.
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tPUSH))
.add(predOps(ARMCC::AL))
.addReg(ARM::LR);
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::STMDB_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ARM::LR);
}
// Emit the DWARF info about the change in stack as well as where to find the
// previous link register
if (!MF.getTarget().getMCAsmInfo().usesWindowsCFI()) {
CFIInstBuilder CFIBuilder(AllocMBB, MachineInstr::NoFlags);
CFIBuilder.buildDefCFAOffset(12);
CFIBuilder.buildOffset(ARM::LR, -12);
}
// Call __morestack().
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tBL))
.add(predOps(ARMCC::AL))
.addExternalSymbol("__morestack");
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::BL))
.addExternalSymbol("__morestack");
}
// pop {lr} - Restore return address of this original function.
if (Thumb) {
if (ST->isThumb1Only()) {
BuildMI(AllocMBB, DL, TII.get(ARM::tPOP))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0);
BuildMI(AllocMBB, DL, TII.get(ARM::tMOVr), ARM::LR)
.addReg(ScratchReg0)
.add(predOps(ARMCC::AL));
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::t2LDR_POST))
.addReg(ARM::LR, RegState::Define)
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.addImm(4)
.add(predOps(ARMCC::AL));
}
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ARM::LR);
}
// Restore SR0 and SR1 in case of __morestack() was called.
// __morestack() will skip PostStackMBB block so we need to restore
// scratch registers from here.
// pop {SR0, SR1}
if (Thumb) {
BuildMI(AllocMBB, DL, TII.get(ARM::tPOP))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Update the CFA offset now that we've popped
if (!MF.getTarget().getMCAsmInfo().usesWindowsCFI())
CFIInstBuilder(AllocMBB, MachineInstr::NoFlags).buildDefCFAOffset(0);
// Return from this function.
BuildMI(AllocMBB, DL, TII.get(ST->getReturnOpcode())).add(predOps(ARMCC::AL));
// Restore SR0 and SR1 in case of __morestack() was not called.
// pop {SR0, SR1}
if (Thumb) {
BuildMI(PostStackMBB, DL, TII.get(ARM::tPOP))
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
BuildMI(PostStackMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.add(predOps(ARMCC::AL))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Update the CFA offset now that we've popped
if (!MF.getTarget().getMCAsmInfo().usesWindowsCFI()) {
CFIInstBuilder CFIBuilder(PostStackMBB, MachineInstr::NoFlags);
CFIBuilder.buildDefCFAOffset(0);
// Tell debuggers that r4 and r5 are now the same as they were in the
// previous function, that they're the "Same Value".
CFIBuilder.buildSameValue(ScratchReg0);
CFIBuilder.buildSameValue(ScratchReg1);
}
// Organizing MBB lists
PostStackMBB->addSuccessor(&PrologueMBB);
AllocMBB->addSuccessor(PostStackMBB);
GetMBB->addSuccessor(PostStackMBB);
GetMBB->addSuccessor(AllocMBB);
McrMBB->addSuccessor(GetMBB);
PrevStackMBB->addSuccessor(McrMBB);
#ifdef EXPENSIVE_CHECKS
MF.verify();
#endif
}