| //===-- X86WinEHUnwindV2.cpp - Win x64 Unwind v2 ----------------*- C++ -*-===// |
| // |
| // 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 |
| // |
| //===----------------------------------------------------------------------===// |
| /// |
| /// Implements the analysis required to detect if a function can use Unwind v2 |
| /// information, and emits the neccesary pseudo instructions used by MC to |
| /// generate the unwind info. |
| /// |
| //===----------------------------------------------------------------------===// |
| |
| #include "MCTargetDesc/X86BaseInfo.h" |
| #include "X86.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/TargetInstrInfo.h" |
| #include "llvm/CodeGen/TargetSubtargetInfo.h" |
| #include "llvm/IR/DiagnosticInfo.h" |
| #include "llvm/IR/Module.h" |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "x86-wineh-unwindv2" |
| |
| STATISTIC(MeetsUnwindV2Criteria, |
| "Number of functions that meet Unwind v2 criteria"); |
| STATISTIC(FailsUnwindV2Criteria, |
| "Number of functions that fail Unwind v2 criteria"); |
| |
| static cl::opt<unsigned> MaximumUnwindCodes( |
| "x86-wineh-unwindv2-max-unwind-codes", cl::Hidden, |
| cl::desc("Maximum number of unwind codes permitted in each unwind info."), |
| cl::init(UINT8_MAX)); |
| |
| static cl::opt<unsigned> |
| ForceMode("x86-wineh-unwindv2-force-mode", cl::Hidden, |
| cl::desc("Overwrites the Unwind v2 mode for testing purposes.")); |
| |
| namespace { |
| |
| class X86WinEHUnwindV2 : public MachineFunctionPass { |
| public: |
| static char ID; |
| |
| X86WinEHUnwindV2() : MachineFunctionPass(ID) { |
| initializeX86WinEHUnwindV2Pass(*PassRegistry::getPassRegistry()); |
| } |
| |
| StringRef getPassName() const override { return "WinEH Unwind V2"; } |
| |
| bool runOnMachineFunction(MachineFunction &MF) override; |
| |
| private: |
| /// Rejects the current function due to an internal error within LLVM. |
| static bool rejectCurrentFunctionInternalError(const MachineFunction &MF, |
| WinX64EHUnwindV2Mode Mode, |
| StringRef Reason); |
| }; |
| |
| enum class FunctionState { |
| InProlog, |
| HasProlog, |
| InEpilog, |
| FinishedEpilog, |
| }; |
| |
| } // end anonymous namespace |
| |
| char X86WinEHUnwindV2::ID = 0; |
| |
| INITIALIZE_PASS(X86WinEHUnwindV2, "x86-wineh-unwindv2", |
| "Analyze and emit instructions for Win64 Unwind v2", false, |
| false) |
| |
| FunctionPass *llvm::createX86WinEHUnwindV2Pass() { |
| return new X86WinEHUnwindV2(); |
| } |
| |
| DebugLoc findDebugLoc(const MachineBasicBlock &MBB) { |
| for (const MachineInstr &MI : MBB) |
| if (MI.getDebugLoc()) |
| return MI.getDebugLoc(); |
| |
| return DebugLoc::getUnknown(); |
| } |
| |
| bool X86WinEHUnwindV2::runOnMachineFunction(MachineFunction &MF) { |
| WinX64EHUnwindV2Mode Mode = |
| ForceMode.getNumOccurrences() |
| ? static_cast<WinX64EHUnwindV2Mode>(ForceMode.getValue()) |
| : MF.getFunction().getParent()->getWinX64EHUnwindV2Mode(); |
| |
| if (Mode == WinX64EHUnwindV2Mode::Disabled) |
| return false; |
| |
| // Current state of processing the function. We'll assume that all functions |
| // start with a prolog. |
| FunctionState State = FunctionState::InProlog; |
| |
| // Prolog information. |
| SmallVector<int64_t> PushedRegs; |
| bool HasStackAlloc = false; |
| unsigned ApproximatePrologCodeCount = 0; |
| |
| // Requested changes. |
| SmallVector<MachineInstr *> UnwindV2StartLocations; |
| |
| for (MachineBasicBlock &MBB : MF) { |
| // Current epilog information. We assume that epilogs cannot cross basic |
| // block boundaries. |
| unsigned PoppedRegCount = 0; |
| bool HasStackDealloc = false; |
| MachineInstr *UnwindV2StartLocation = nullptr; |
| |
| for (MachineInstr &MI : MBB) { |
| switch (MI.getOpcode()) { |
| // |
| // Prolog handling. |
| // |
| case X86::SEH_PushReg: |
| if (State != FunctionState::InProlog) |
| llvm_unreachable("SEH_PushReg outside of prolog"); |
| ApproximatePrologCodeCount++; |
| PushedRegs.push_back(MI.getOperand(0).getImm()); |
| break; |
| |
| case X86::SEH_StackAlloc: |
| case X86::SEH_SetFrame: |
| if (State != FunctionState::InProlog) |
| llvm_unreachable("SEH_StackAlloc or SEH_SetFrame outside of prolog"); |
| // Assume a large alloc... |
| ApproximatePrologCodeCount += |
| (MI.getOpcode() == X86::SEH_StackAlloc) ? 3 : 1; |
| HasStackAlloc = true; |
| break; |
| |
| case X86::SEH_SaveReg: |
| case X86::SEH_SaveXMM: |
| if (State != FunctionState::InProlog) |
| llvm_unreachable("SEH_SaveXMM or SEH_SaveReg outside of prolog"); |
| // Assume a big reg... |
| ApproximatePrologCodeCount += 3; |
| break; |
| |
| case X86::SEH_PushFrame: |
| if (State != FunctionState::InProlog) |
| llvm_unreachable("SEH_PushFrame outside of prolog"); |
| ApproximatePrologCodeCount++; |
| break; |
| |
| case X86::SEH_EndPrologue: |
| if (State != FunctionState::InProlog) |
| llvm_unreachable("SEH_EndPrologue outside of prolog"); |
| State = FunctionState::HasProlog; |
| break; |
| |
| // |
| // Epilog handling. |
| // |
| case X86::SEH_BeginEpilogue: |
| if (State != FunctionState::HasProlog) |
| llvm_unreachable("SEH_BeginEpilogue in prolog or another epilog"); |
| State = FunctionState::InEpilog; |
| break; |
| |
| case X86::SEH_EndEpilogue: |
| if (State != FunctionState::InEpilog) |
| llvm_unreachable("SEH_EndEpilogue outside of epilog"); |
| if (HasStackAlloc != HasStackDealloc) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, |
| "The prolog made a stack allocation, " |
| "but the epilog did not deallocate it"); |
| if (PoppedRegCount != PushedRegs.size()) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, |
| "The prolog pushed more registers than " |
| "the epilog popped"); |
| |
| // If we didn't find the start location, then use the end of the |
| // epilog. |
| if (!UnwindV2StartLocation) |
| UnwindV2StartLocation = &MI; |
| UnwindV2StartLocations.push_back(UnwindV2StartLocation); |
| State = FunctionState::FinishedEpilog; |
| break; |
| |
| case X86::MOV64rr: |
| case X86::ADD64ri32: |
| if (State == FunctionState::InEpilog) { |
| // If the prolog contains a stack allocation, then the first |
| // instruction in the epilog must be to adjust the stack pointer. |
| if (!HasStackAlloc) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, |
| "The epilog is deallocating a stack " |
| "allocation, but the prolog did " |
| "not allocate one"); |
| if (HasStackDealloc) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, |
| "The epilog is deallocating the stack " |
| "allocation more than once"); |
| if (PoppedRegCount > 0) |
| llvm_unreachable( |
| "Should have raised an error: either popping before " |
| "deallocating or deallocating without an allocation"); |
| |
| HasStackDealloc = true; |
| } else if (State == FunctionState::FinishedEpilog) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, "Unexpected mov or add instruction after the epilog"); |
| break; |
| |
| case X86::POP64r: |
| if (State == FunctionState::InEpilog) { |
| // After the stack pointer has been adjusted, the epilog must |
| // POP each register in reverse order of the PUSHes in the prolog. |
| PoppedRegCount++; |
| if (HasStackAlloc != HasStackDealloc) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, |
| "Cannot pop registers before the stack " |
| "allocation has been deallocated"); |
| if (PoppedRegCount > PushedRegs.size()) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, |
| "The epilog is popping more registers than the prolog pushed"); |
| if (PushedRegs[PushedRegs.size() - PoppedRegCount] != |
| MI.getOperand(0).getReg()) |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, |
| "The epilog is popping a registers in " |
| "a different order than the " |
| "prolog pushed them"); |
| |
| // Unwind v2 records the size of the epilog not from where we place |
| // SEH_BeginEpilogue (as that contains the instruction to adjust the |
| // stack pointer) but from the first POP instruction (if there is |
| // one). |
| if (!UnwindV2StartLocation) { |
| assert(PoppedRegCount == 1); |
| UnwindV2StartLocation = &MI; |
| } |
| } else if (State == FunctionState::FinishedEpilog) |
| // Unexpected instruction after the epilog. |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, "Registers are being popped after the epilog"); |
| break; |
| |
| default: |
| if (MI.isTerminator()) { |
| if (State == FunctionState::FinishedEpilog) |
| // Found the terminator after the epilog, we're now ready for |
| // another epilog. |
| State = FunctionState::HasProlog; |
| else if (State == FunctionState::InEpilog) |
| llvm_unreachable("Terminator in the middle of the epilog"); |
| } else if (!MI.isDebugOrPseudoInstr()) { |
| if ((State == FunctionState::FinishedEpilog) || |
| (State == FunctionState::InEpilog)) |
| // Unknown instruction in or after the epilog. |
| return rejectCurrentFunctionInternalError( |
| MF, Mode, "Unexpected instruction in or after the epilog"); |
| } |
| } |
| } |
| } |
| |
| if (UnwindV2StartLocations.empty()) { |
| assert(State == FunctionState::InProlog && |
| "If there are no epilogs, then there should be no prolog"); |
| return false; |
| } |
| |
| MachineBasicBlock &FirstMBB = MF.front(); |
| // Assume +1 for the "header" UOP_Epilog that contains the epilog size, and |
| // that we won't be able to use the "last epilog at the end of function" |
| // optimization. |
| if (ApproximatePrologCodeCount + UnwindV2StartLocations.size() + 1 > |
| static_cast<unsigned>(MaximumUnwindCodes)) { |
| if (Mode == WinX64EHUnwindV2Mode::Required) |
| MF.getFunction().getContext().diagnose(DiagnosticInfoGenericWithLoc( |
| "Windows x64 Unwind v2 is required, but the function '" + |
| MF.getName() + |
| "' has too many unwind codes. Try splitting the function or " |
| "reducing the number of places where it exits early with a tail " |
| "call.", |
| MF.getFunction(), findDebugLoc(FirstMBB))); |
| |
| FailsUnwindV2Criteria++; |
| return false; |
| } |
| |
| MeetsUnwindV2Criteria++; |
| |
| // Emit the pseudo instruction that marks the start of each epilog. |
| const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); |
| for (MachineInstr *MI : UnwindV2StartLocations) { |
| BuildMI(*MI->getParent(), MI, MI->getDebugLoc(), |
| TII->get(X86::SEH_UnwindV2Start)); |
| } |
| // Note that the function is using Unwind v2. |
| BuildMI(FirstMBB, FirstMBB.front(), findDebugLoc(FirstMBB), |
| TII->get(X86::SEH_UnwindVersion)) |
| .addImm(2); |
| |
| return true; |
| } |
| |
| bool X86WinEHUnwindV2::rejectCurrentFunctionInternalError( |
| const MachineFunction &MF, WinX64EHUnwindV2Mode Mode, StringRef Reason) { |
| if (Mode == WinX64EHUnwindV2Mode::Required) |
| reportFatalInternalError("Windows x64 Unwind v2 is required, but LLVM has " |
| "generated incompatible code in function '" + |
| MF.getName() + "': " + Reason); |
| |
| FailsUnwindV2Criteria++; |
| return false; |
| } |
