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//===- SelectionDAGBuilder.h - Selection-DAG building -----------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This implements routines for translating from LLVM IR into SelectionDAG IR.
#include "StatepointLowering.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Statepoint.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MachineValueType.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <utility>
#include <vector>
namespace llvm {
class AllocaInst;
class AtomicCmpXchgInst;
class AtomicRMWInst;
class BasicBlock;
class BranchInst;
class CallInst;
class CallBrInst;
class CatchPadInst;
class CatchReturnInst;
class CatchSwitchInst;
class CleanupPadInst;
class CleanupReturnInst;
class Constant;
class ConstantInt;
class ConstrainedFPIntrinsic;
class DbgValueInst;
class DataLayout;
class DIExpression;
class DILocalVariable;
class DILocation;
class FenceInst;
class FunctionLoweringInfo;
class GCFunctionInfo;
class GCRelocateInst;
class GCResultInst;
class IndirectBrInst;
class InvokeInst;
class LandingPadInst;
class LLVMContext;
class LoadInst;
class MachineBasicBlock;
class PHINode;
class ResumeInst;
class ReturnInst;
class SDDbgValue;
class StoreInst;
class SwitchInst;
class TargetLibraryInfo;
class TargetMachine;
class Type;
class VAArgInst;
class UnreachableInst;
class Use;
class User;
class Value;
/// SelectionDAGBuilder - This is the common target-independent lowering
/// implementation that is parameterized by a TargetLowering object.
class SelectionDAGBuilder {
/// CurInst - The current instruction being visited
const Instruction *CurInst = nullptr;
DenseMap<const Value*, SDValue> NodeMap;
/// UnusedArgNodeMap - Maps argument value for unused arguments. This is used
/// to preserve debug information for incoming arguments.
DenseMap<const Value*, SDValue> UnusedArgNodeMap;
/// DanglingDebugInfo - Helper type for DanglingDebugInfoMap.
class DanglingDebugInfo {
const DbgValueInst* DI = nullptr;
DebugLoc dl;
unsigned SDNodeOrder = 0;
DanglingDebugInfo() = default;
DanglingDebugInfo(const DbgValueInst *di, DebugLoc DL, unsigned SDNO)
: DI(di), dl(std::move(DL)), SDNodeOrder(SDNO) {}
const DbgValueInst* getDI() { return DI; }
DebugLoc getdl() { return dl; }
unsigned getSDNodeOrder() { return SDNodeOrder; }
/// DanglingDebugInfoVector - Helper type for DanglingDebugInfoMap.
typedef std::vector<DanglingDebugInfo> DanglingDebugInfoVector;
/// DanglingDebugInfoMap - Keeps track of dbg_values for which we have not
/// yet seen the referent. We defer handling these until we do see it.
DenseMap<const Value*, DanglingDebugInfoVector> DanglingDebugInfoMap;
/// PendingLoads - Loads are not emitted to the program immediately. We bunch
/// them up and then emit token factor nodes when possible. This allows us to
/// get simple disambiguation between loads without worrying about alias
/// analysis.
SmallVector<SDValue, 8> PendingLoads;
/// State used while lowering a statepoint sequence (gc_statepoint,
/// gc_relocate, and gc_result). See StatepointLowering.hpp/cpp for details.
StatepointLoweringState StatepointLowering;
/// PendingExports - CopyToReg nodes that copy values to virtual registers
/// for export to other blocks need to be emitted before any terminator
/// instruction, but they have no other ordering requirements. We bunch them
/// up and the emit a single tokenfactor for them just before terminator
/// instructions.
SmallVector<SDValue, 8> PendingExports;
/// SDNodeOrder - A unique monotonically increasing number used to order the
/// SDNodes we create.
unsigned SDNodeOrder;
enum CaseClusterKind {
/// A cluster of adjacent case labels with the same destination, or just one
/// case.
/// A cluster of cases suitable for jump table lowering.
/// A cluster of cases suitable for bit test lowering.
/// A cluster of case labels.
struct CaseCluster {
CaseClusterKind Kind;
const ConstantInt *Low, *High;
union {
MachineBasicBlock *MBB;
unsigned JTCasesIndex;
unsigned BTCasesIndex;
BranchProbability Prob;
static CaseCluster range(const ConstantInt *Low, const ConstantInt *High,
MachineBasicBlock *MBB, BranchProbability Prob) {
CaseCluster C;
C.Kind = CC_Range;
C.Low = Low;
C.High = High;
C.Prob = Prob;
return C;
static CaseCluster jumpTable(const ConstantInt *Low,
const ConstantInt *High, unsigned JTCasesIndex,
BranchProbability Prob) {
CaseCluster C;
C.Kind = CC_JumpTable;
C.Low = Low;
C.High = High;
C.JTCasesIndex = JTCasesIndex;
C.Prob = Prob;
return C;
static CaseCluster bitTests(const ConstantInt *Low, const ConstantInt *High,
unsigned BTCasesIndex, BranchProbability Prob) {
CaseCluster C;
C.Kind = CC_BitTests;
C.Low = Low;
C.High = High;
C.BTCasesIndex = BTCasesIndex;
C.Prob = Prob;
return C;
using CaseClusterVector = std::vector<CaseCluster>;
using CaseClusterIt = CaseClusterVector::iterator;
struct CaseBits {
uint64_t Mask = 0;
MachineBasicBlock* BB = nullptr;
unsigned Bits = 0;
BranchProbability ExtraProb;
CaseBits() = default;
CaseBits(uint64_t mask, MachineBasicBlock* bb, unsigned bits,
BranchProbability Prob):
Mask(mask), BB(bb), Bits(bits), ExtraProb(Prob) {}
using CaseBitsVector = std::vector<CaseBits>;
/// Sort Clusters and merge adjacent cases.
void sortAndRangeify(CaseClusterVector &Clusters);
/// CaseBlock - This structure is used to communicate between
/// SelectionDAGBuilder and SDISel for the code generation of additional basic
/// blocks needed by multi-case switch statements.
struct CaseBlock {
// CC - the condition code to use for the case block's setcc node
ISD::CondCode CC;
// CmpLHS/CmpRHS/CmpMHS - The LHS/MHS/RHS of the comparison to emit.
// Emit by default LHS op RHS. MHS is used for range comparisons:
// If MHS is not null: (LHS <= MHS) and (MHS <= RHS).
const Value *CmpLHS, *CmpMHS, *CmpRHS;
// TrueBB/FalseBB - the block to branch to if the setcc is true/false.
MachineBasicBlock *TrueBB, *FalseBB;
// ThisBB - the block into which to emit the code for the setcc and branches
MachineBasicBlock *ThisBB;
/// The debug location of the instruction this CaseBlock was
/// produced from.
// TrueProb/FalseProb - branch weights.
BranchProbability TrueProb, FalseProb;
CaseBlock(ISD::CondCode cc, const Value *cmplhs, const Value *cmprhs,
const Value *cmpmiddle, MachineBasicBlock *truebb,
MachineBasicBlock *falsebb, MachineBasicBlock *me,
SDLoc dl,
BranchProbability trueprob = BranchProbability::getUnknown(),
BranchProbability falseprob = BranchProbability::getUnknown())
: CC(cc), CmpLHS(cmplhs), CmpMHS(cmpmiddle), CmpRHS(cmprhs),
TrueBB(truebb), FalseBB(falsebb), ThisBB(me), DL(dl),
TrueProb(trueprob), FalseProb(falseprob) {}
struct JumpTable {
/// Reg - the virtual register containing the index of the jump table entry
//. to jump to.
unsigned Reg;
/// JTI - the JumpTableIndex for this jump table in the function.
unsigned JTI;
/// MBB - the MBB into which to emit the code for the indirect jump.
MachineBasicBlock *MBB;
/// Default - the MBB of the default bb, which is a successor of the range
/// check MBB. This is when updating PHI nodes in successors.
MachineBasicBlock *Default;
JumpTable(unsigned R, unsigned J, MachineBasicBlock *M,
MachineBasicBlock *D): Reg(R), JTI(J), MBB(M), Default(D) {}
struct JumpTableHeader {
APInt First;
APInt Last;
const Value *SValue;
MachineBasicBlock *HeaderBB;
bool Emitted;
JumpTableHeader(APInt F, APInt L, const Value *SV, MachineBasicBlock *H,
bool E = false)
: First(std::move(F)), Last(std::move(L)), SValue(SV), HeaderBB(H),
Emitted(E) {}
using JumpTableBlock = std::pair<JumpTableHeader, JumpTable>;
struct BitTestCase {
uint64_t Mask;
MachineBasicBlock *ThisBB;
MachineBasicBlock *TargetBB;
BranchProbability ExtraProb;
BitTestCase(uint64_t M, MachineBasicBlock* T, MachineBasicBlock* Tr,
BranchProbability Prob):
Mask(M), ThisBB(T), TargetBB(Tr), ExtraProb(Prob) {}
using BitTestInfo = SmallVector<BitTestCase, 3>;
struct BitTestBlock {
APInt First;
APInt Range;
const Value *SValue;
unsigned Reg;
bool Emitted;
bool ContiguousRange;
MachineBasicBlock *Parent;
MachineBasicBlock *Default;
BitTestInfo Cases;
BranchProbability Prob;
BranchProbability DefaultProb;
BitTestBlock(APInt F, APInt R, const Value *SV, unsigned Rg, MVT RgVT,
bool E, bool CR, MachineBasicBlock *P, MachineBasicBlock *D,
BitTestInfo C, BranchProbability Pr)
: First(std::move(F)), Range(std::move(R)), SValue(SV), Reg(Rg),
RegVT(RgVT), Emitted(E), ContiguousRange(CR), Parent(P), Default(D),
Cases(std::move(C)), Prob(Pr) {}
/// Return the range of value in [First..Last].
uint64_t getJumpTableRange(const CaseClusterVector &Clusters, unsigned First,
unsigned Last) const;
/// Return the number of cases in [First..Last].
uint64_t getJumpTableNumCases(const SmallVectorImpl<unsigned> &TotalCases,
unsigned First, unsigned Last) const;
/// Build a jump table cluster from Clusters[First..Last]. Returns false if it
/// decides it's not a good idea.
bool buildJumpTable(const CaseClusterVector &Clusters, unsigned First,
unsigned Last, const SwitchInst *SI,
MachineBasicBlock *DefaultMBB, CaseCluster &JTCluster);
/// Find clusters of cases suitable for jump table lowering.
void findJumpTables(CaseClusterVector &Clusters, const SwitchInst *SI,
MachineBasicBlock *DefaultMBB);
/// Build a bit test cluster from Clusters[First..Last]. Returns false if it
/// decides it's not a good idea.
bool buildBitTests(CaseClusterVector &Clusters, unsigned First, unsigned Last,
const SwitchInst *SI, CaseCluster &BTCluster);
/// Find clusters of cases suitable for bit test lowering.
void findBitTestClusters(CaseClusterVector &Clusters, const SwitchInst *SI);
struct SwitchWorkListItem {
MachineBasicBlock *MBB;
CaseClusterIt FirstCluster;
CaseClusterIt LastCluster;
const ConstantInt *GE;
const ConstantInt *LT;
BranchProbability DefaultProb;
using SwitchWorkList = SmallVector<SwitchWorkListItem, 4>;
/// Determine the rank by weight of CC in [First,Last]. If CC has more weight
/// than each cluster in the range, its rank is 0.
static unsigned caseClusterRank(const CaseCluster &CC, CaseClusterIt First,
CaseClusterIt Last);
/// Emit comparison and split W into two subtrees.
void splitWorkItem(SwitchWorkList &WorkList, const SwitchWorkListItem &W,
Value *Cond, MachineBasicBlock *SwitchMBB);
/// Lower W.
void lowerWorkItem(SwitchWorkListItem W, Value *Cond,
MachineBasicBlock *SwitchMBB,
MachineBasicBlock *DefaultMBB);
/// Peel the top probability case if it exceeds the threshold
MachineBasicBlock *peelDominantCaseCluster(const SwitchInst &SI,
CaseClusterVector &Clusters,
BranchProbability &PeeledCaseProb);
/// A class which encapsulates all of the information needed to generate a
/// stack protector check and signals to isel via its state being initialized
/// that a stack protector needs to be generated.
/// *NOTE* The following is a high level documentation of SelectionDAG Stack
/// Protector Generation. The reason that it is placed here is for a lack of
/// other good places to stick it.
/// High Level Overview of SelectionDAG Stack Protector Generation:
/// Previously, generation of stack protectors was done exclusively in the
/// pre-SelectionDAG Codegen LLVM IR Pass "Stack Protector". This necessitated
/// splitting basic blocks at the IR level to create the success/failure basic
/// blocks in the tail of the basic block in question. As a result of this,
/// calls that would have qualified for the sibling call optimization were no
/// longer eligible for optimization since said calls were no longer right in
/// the "tail position" (i.e. the immediate predecessor of a ReturnInst
/// instruction).
/// Then it was noticed that since the sibling call optimization causes the
/// callee to reuse the caller's stack, if we could delay the generation of
/// the stack protector check until later in CodeGen after the sibling call
/// decision was made, we get both the tail call optimization and the stack
/// protector check!
/// A few goals in solving this problem were:
/// 1. Preserve the architecture independence of stack protector generation.
/// 2. Preserve the normal IR level stack protector check for platforms like
/// OpenBSD for which we support platform-specific stack protector
/// generation.
/// The main problem that guided the present solution is that one can not
/// solve this problem in an architecture independent manner at the IR level
/// only. This is because:
/// 1. The decision on whether or not to perform a sibling call on certain
/// platforms (for instance i386) requires lower level information
/// related to available registers that can not be known at the IR level.
/// 2. Even if the previous point were not true, the decision on whether to
/// perform a tail call is done in LowerCallTo in SelectionDAG which
/// occurs after the Stack Protector Pass. As a result, one would need to
/// put the relevant callinst into the stack protector check success
/// basic block (where the return inst is placed) and then move it back
/// later at SelectionDAG/MI time before the stack protector check if the
/// tail call optimization failed. The MI level option was nixed
/// immediately since it would require platform-specific pattern
/// matching. The SelectionDAG level option was nixed because
/// SelectionDAG only processes one IR level basic block at a time
/// implying one could not create a DAG Combine to move the callinst.
/// To get around this problem a few things were realized:
/// 1. While one can not handle multiple IR level basic blocks at the
/// SelectionDAG Level, one can generate multiple machine basic blocks
/// for one IR level basic block. This is how we handle bit tests and
/// switches.
/// 2. At the MI level, tail calls are represented via a special return
/// MIInst called "tcreturn". Thus if we know the basic block in which we
/// wish to insert the stack protector check, we get the correct behavior
/// by always inserting the stack protector check right before the return
/// statement. This is a "magical transformation" since no matter where
/// the stack protector check intrinsic is, we always insert the stack
/// protector check code at the end of the BB.
/// Given the aforementioned constraints, the following solution was devised:
/// 1. On platforms that do not support SelectionDAG stack protector check
/// generation, allow for the normal IR level stack protector check
/// generation to continue.
/// 2. On platforms that do support SelectionDAG stack protector check
/// generation:
/// a. Use the IR level stack protector pass to decide if a stack
/// protector is required/which BB we insert the stack protector check
/// in by reusing the logic already therein. If we wish to generate a
/// stack protector check in a basic block, we place a special IR
/// intrinsic called llvm.stackprotectorcheck right before the BB's
/// returninst or if there is a callinst that could potentially be
/// sibling call optimized, before the call inst.
/// b. Then when a BB with said intrinsic is processed, we codegen the BB
/// normally via SelectBasicBlock. In said process, when we visit the
/// stack protector check, we do not actually emit anything into the
/// BB. Instead, we just initialize the stack protector descriptor
/// class (which involves stashing information/creating the success
/// mbbb and the failure mbb if we have not created one for this
/// function yet) and export the guard variable that we are going to
/// compare.
/// c. After we finish selecting the basic block, in FinishBasicBlock if
/// the StackProtectorDescriptor attached to the SelectionDAGBuilder is
/// initialized, we produce the validation code with one of these
/// techniques:
/// 1) with a call to a guard check function
/// 2) with inlined instrumentation
/// 1) We insert a call to the check function before the terminator.
/// 2) We first find a splice point in the parent basic block
/// before the terminator and then splice the terminator of said basic
/// block into the success basic block. Then we code-gen a new tail for
/// the parent basic block consisting of the two loads, the comparison,
/// and finally two branches to the success/failure basic blocks. We
/// conclude by code-gening the failure basic block if we have not
/// code-gened it already (all stack protector checks we generate in
/// the same function, use the same failure basic block).
class StackProtectorDescriptor {
StackProtectorDescriptor() = default;
/// Returns true if all fields of the stack protector descriptor are
/// initialized implying that we should/are ready to emit a stack protector.
bool shouldEmitStackProtector() const {
return ParentMBB && SuccessMBB && FailureMBB;
bool shouldEmitFunctionBasedCheckStackProtector() const {
return ParentMBB && !SuccessMBB && !FailureMBB;
/// Initialize the stack protector descriptor structure for a new basic
/// block.
void initialize(const BasicBlock *BB, MachineBasicBlock *MBB,
bool FunctionBasedInstrumentation) {
// Make sure we are not initialized yet.
assert(!shouldEmitStackProtector() && "Stack Protector Descriptor is "
"already initialized!");
ParentMBB = MBB;
if (!FunctionBasedInstrumentation) {
SuccessMBB = AddSuccessorMBB(BB, MBB, /* IsLikely */ true);
FailureMBB = AddSuccessorMBB(BB, MBB, /* IsLikely */ false, FailureMBB);
/// Reset state that changes when we handle different basic blocks.
/// This currently includes:
/// 1. The specific basic block we are generating a
/// stack protector for (ParentMBB).
/// 2. The successor machine basic block that will contain the tail of
/// parent mbb after we create the stack protector check (SuccessMBB). This
/// BB is visited only on stack protector check success.
void resetPerBBState() {
ParentMBB = nullptr;
SuccessMBB = nullptr;
/// Reset state that only changes when we switch functions.
/// This currently includes:
/// 1. FailureMBB since we reuse the failure code path for all stack
/// protector checks created in an individual function.
/// 2.The guard variable since the guard variable we are checking against is
/// always the same.
void resetPerFunctionState() {
FailureMBB = nullptr;
MachineBasicBlock *getParentMBB() { return ParentMBB; }
MachineBasicBlock *getSuccessMBB() { return SuccessMBB; }
MachineBasicBlock *getFailureMBB() { return FailureMBB; }
/// The basic block for which we are generating the stack protector.
/// As a result of stack protector generation, we will splice the
/// terminators of this basic block into the successor mbb SuccessMBB and
/// replace it with a compare/branch to the successor mbbs
/// SuccessMBB/FailureMBB depending on whether or not the stack protector
/// was violated.
MachineBasicBlock *ParentMBB = nullptr;
/// A basic block visited on stack protector check success that contains the
/// terminators of ParentMBB.
MachineBasicBlock *SuccessMBB = nullptr;
/// This basic block visited on stack protector check failure that will
/// contain a call to __stack_chk_fail().
MachineBasicBlock *FailureMBB = nullptr;
/// Add a successor machine basic block to ParentMBB. If the successor mbb
/// has not been created yet (i.e. if SuccMBB = 0), then the machine basic
/// block will be created. Assign a large weight if IsLikely is true.
MachineBasicBlock *AddSuccessorMBB(const BasicBlock *BB,
MachineBasicBlock *ParentMBB,
bool IsLikely,
MachineBasicBlock *SuccMBB = nullptr);
const TargetMachine &TM;
/// Lowest valid SDNodeOrder. The special case 0 is reserved for scheduling
/// nodes without a corresponding SDNode.
static const unsigned LowestSDNodeOrder = 1;
SelectionDAG &DAG;
const DataLayout *DL = nullptr;
AliasAnalysis *AA = nullptr;
const TargetLibraryInfo *LibInfo;
/// SwitchCases - Vector of CaseBlock structures used to communicate
/// SwitchInst code generation information.
std::vector<CaseBlock> SwitchCases;
/// JTCases - Vector of JumpTable structures used to communicate
/// SwitchInst code generation information.
std::vector<JumpTableBlock> JTCases;
/// BitTestCases - Vector of BitTestBlock structures used to communicate
/// SwitchInst code generation information.
std::vector<BitTestBlock> BitTestCases;
/// A StackProtectorDescriptor structure used to communicate stack protector
/// information in between SelectBasicBlock and FinishBasicBlock.
StackProtectorDescriptor SPDescriptor;
// Emit PHI-node-operand constants only once even if used by multiple
// PHI nodes.
DenseMap<const Constant *, unsigned> ConstantsOut;
/// FuncInfo - Information about the function as a whole.
FunctionLoweringInfo &FuncInfo;
/// GFI - Garbage collection metadata for the function.
GCFunctionInfo *GFI;
/// LPadToCallSiteMap - Map a landing pad to the call site indexes.
DenseMap<MachineBasicBlock *, SmallVector<unsigned, 4>> LPadToCallSiteMap;
/// HasTailCall - This is set to true if a call in the current
/// block has been translated as a tail call. In this case,
/// no subsequent DAG nodes should be created.
bool HasTailCall = false;
LLVMContext *Context;
SelectionDAGBuilder(SelectionDAG &dag, FunctionLoweringInfo &funcinfo,
CodeGenOpt::Level ol)
: SDNodeOrder(LowestSDNodeOrder), TM(dag.getTarget()), DAG(dag),
FuncInfo(funcinfo) {}
void init(GCFunctionInfo *gfi, AliasAnalysis *AA,
const TargetLibraryInfo *li);
/// Clear out the current SelectionDAG and the associated state and prepare
/// this SelectionDAGBuilder object to be used for a new block. This doesn't
/// clear out information about additional blocks that are needed to complete
/// switch lowering or PHI node updating; that information is cleared out as
/// it is consumed.
void clear();
/// Clear the dangling debug information map. This function is separated from
/// the clear so that debug information that is dangling in a basic block can
/// be properly resolved in a different basic block. This allows the
/// SelectionDAG to resolve dangling debug information attached to PHI nodes.
void clearDanglingDebugInfo();
/// Return the current virtual root of the Selection DAG, flushing any
/// PendingLoad items. This must be done before emitting a store or any other
/// node that may need to be ordered after any prior load instructions.
SDValue getRoot();
/// Similar to getRoot, but instead of flushing all the PendingLoad items,
/// flush all the PendingExports items. It is necessary to do this before
/// emitting a terminator instruction.
SDValue getControlRoot();
SDLoc getCurSDLoc() const {
return SDLoc(CurInst, SDNodeOrder);
DebugLoc getCurDebugLoc() const {
return CurInst ? CurInst->getDebugLoc() : DebugLoc();
void CopyValueToVirtualRegister(const Value *V, unsigned Reg);
void visit(const Instruction &I);
void visit(unsigned Opcode, const User &I);
/// If there was virtual register allocated for the value V emit CopyFromReg
/// of the specified type Ty. Return empty SDValue() otherwise.
SDValue getCopyFromRegs(const Value *V, Type *Ty);
/// If we have dangling debug info that describes \p Variable, or an
/// overlapping part of variable considering the \p Expr, then this method
/// weill drop that debug info as it isn't valid any longer.
void dropDanglingDebugInfo(const DILocalVariable *Variable,
const DIExpression *Expr);
// If we saw an earlier dbg_value referring to V, generate the debug data
// structures now that we've seen its definition.
void resolveDanglingDebugInfo(const Value *V, SDValue Val);
SDValue getValue(const Value *V);
bool findValue(const Value *V) const;
/// Return the SDNode for the specified IR value if it exists.
SDNode *getNodeForIRValue(const Value *V) {
if (NodeMap.find(V) == NodeMap.end())
return nullptr;
return NodeMap[V].getNode();
SDValue getNonRegisterValue(const Value *V);
SDValue getValueImpl(const Value *V);
void setValue(const Value *V, SDValue NewN) {
SDValue &N = NodeMap[V];
assert(!N.getNode() && "Already set a value for this node!");
N = NewN;
void setUnusedArgValue(const Value *V, SDValue NewN) {
SDValue &N = UnusedArgNodeMap[V];
assert(!N.getNode() && "Already set a value for this node!");
N = NewN;
void FindMergedConditions(const Value *Cond, MachineBasicBlock *TBB,
MachineBasicBlock *FBB, MachineBasicBlock *CurBB,
MachineBasicBlock *SwitchBB,
Instruction::BinaryOps Opc, BranchProbability TProb,
BranchProbability FProb, bool InvertCond);
void EmitBranchForMergedCondition(const Value *Cond, MachineBasicBlock *TBB,
MachineBasicBlock *FBB,
MachineBasicBlock *CurBB,
MachineBasicBlock *SwitchBB,
BranchProbability TProb, BranchProbability FProb,
bool InvertCond);
bool ShouldEmitAsBranches(const std::vector<CaseBlock> &Cases);
bool isExportableFromCurrentBlock(const Value *V, const BasicBlock *FromBB);
void CopyToExportRegsIfNeeded(const Value *V);
void ExportFromCurrentBlock(const Value *V);
void LowerCallTo(ImmutableCallSite CS, SDValue Callee, bool IsTailCall,
const BasicBlock *EHPadBB = nullptr);
// Lower range metadata from 0 to N to assert zext to an integer of nearest
// floor power of two.
SDValue lowerRangeToAssertZExt(SelectionDAG &DAG, const Instruction &I,
SDValue Op);
void populateCallLoweringInfo(TargetLowering::CallLoweringInfo &CLI,
const CallBase *Call, unsigned ArgIdx,
unsigned NumArgs, SDValue Callee,
Type *ReturnTy, bool IsPatchPoint);
std::pair<SDValue, SDValue>
lowerInvokable(TargetLowering::CallLoweringInfo &CLI,
const BasicBlock *EHPadBB = nullptr);
/// UpdateSplitBlock - When an MBB was split during scheduling, update the
/// references that need to refer to the last resulting block.
void UpdateSplitBlock(MachineBasicBlock *First, MachineBasicBlock *Last);
/// Describes a gc.statepoint or a gc.statepoint like thing for the purposes
/// of lowering into a STATEPOINT node.
struct StatepointLoweringInfo {
/// Bases[i] is the base pointer for Ptrs[i]. Together they denote the set
/// of gc pointers this STATEPOINT has to relocate.
SmallVector<const Value *, 16> Bases;
SmallVector<const Value *, 16> Ptrs;
/// The set of gc.relocate calls associated with this gc.statepoint.
SmallVector<const GCRelocateInst *, 16> GCRelocates;
/// The full list of gc arguments to the gc.statepoint being lowered.
ArrayRef<const Use> GCArgs;
/// The gc.statepoint instruction.
const Instruction *StatepointInstr = nullptr;
/// The list of gc transition arguments present in the gc.statepoint being
/// lowered.
ArrayRef<const Use> GCTransitionArgs;
/// The ID that the resulting STATEPOINT instruction has to report.
unsigned ID = -1;
/// Information regarding the underlying call instruction.
TargetLowering::CallLoweringInfo CLI;
/// The deoptimization state associated with this gc.statepoint call, if
/// any.
ArrayRef<const Use> DeoptState;
/// Flags associated with the meta arguments being lowered.
uint64_t StatepointFlags = -1;
/// The number of patchable bytes the call needs to get lowered into.
unsigned NumPatchBytes = -1;
/// The exception handling unwind destination, in case this represents an
/// invoke of gc.statepoint.
const BasicBlock *EHPadBB = nullptr;
explicit StatepointLoweringInfo(SelectionDAG &DAG) : CLI(DAG) {}
/// Lower \p SLI into a STATEPOINT instruction.
SDValue LowerAsSTATEPOINT(StatepointLoweringInfo &SI);
// This function is responsible for the whole statepoint lowering process.
// It uniformly handles invoke and call statepoints.
void LowerStatepoint(ImmutableStatepoint ISP,
const BasicBlock *EHPadBB = nullptr);
void LowerCallSiteWithDeoptBundle(const CallBase *Call, SDValue Callee,
const BasicBlock *EHPadBB);
void LowerDeoptimizeCall(const CallInst *CI);
void LowerDeoptimizingReturn();
void LowerCallSiteWithDeoptBundleImpl(const CallBase *Call, SDValue Callee,
const BasicBlock *EHPadBB,
bool VarArgDisallowed,
bool ForceVoidReturnTy);
/// Returns the type of FrameIndex and TargetFrameIndex nodes.
MVT getFrameIndexTy() {
return DAG.getTargetLoweringInfo().getFrameIndexTy(DAG.getDataLayout());
// Terminator instructions.
void visitRet(const ReturnInst &I);
void visitBr(const BranchInst &I);
void visitSwitch(const SwitchInst &I);
void visitIndirectBr(const IndirectBrInst &I);
void visitUnreachable(const UnreachableInst &I);
void visitCleanupRet(const CleanupReturnInst &I);
void visitCatchSwitch(const CatchSwitchInst &I);
void visitCatchRet(const CatchReturnInst &I);
void visitCatchPad(const CatchPadInst &I);
void visitCleanupPad(const CleanupPadInst &CPI);
BranchProbability getEdgeProbability(const MachineBasicBlock *Src,
const MachineBasicBlock *Dst) const;
void addSuccessorWithProb(
MachineBasicBlock *Src, MachineBasicBlock *Dst,
BranchProbability Prob = BranchProbability::getUnknown());
void visitSwitchCase(CaseBlock &CB,
MachineBasicBlock *SwitchBB);
void visitSPDescriptorParent(StackProtectorDescriptor &SPD,
MachineBasicBlock *ParentBB);
void visitSPDescriptorFailure(StackProtectorDescriptor &SPD);
void visitBitTestHeader(BitTestBlock &B, MachineBasicBlock *SwitchBB);
void visitBitTestCase(BitTestBlock &BB,
MachineBasicBlock* NextMBB,
BranchProbability BranchProbToNext,
unsigned Reg,
BitTestCase &B,
MachineBasicBlock *SwitchBB);
void visitJumpTable(JumpTable &JT);
void visitJumpTableHeader(JumpTable &JT, JumpTableHeader &JTH,
MachineBasicBlock *SwitchBB);
// These all get lowered before this pass.
void visitInvoke(const InvokeInst &I);
void visitCallBr(const CallBrInst &I);
void visitResume(const ResumeInst &I);
void visitUnary(const User &I, unsigned Opcode);
void visitFNeg(const User &I) { visitUnary(I, ISD::FNEG); }
void visitBinary(const User &I, unsigned Opcode);
void visitShift(const User &I, unsigned Opcode);
void visitAdd(const User &I) { visitBinary(I, ISD::ADD); }
void visitFAdd(const User &I) { visitBinary(I, ISD::FADD); }
void visitSub(const User &I) { visitBinary(I, ISD::SUB); }
void visitFSub(const User &I);
void visitMul(const User &I) { visitBinary(I, ISD::MUL); }
void visitFMul(const User &I) { visitBinary(I, ISD::FMUL); }
void visitURem(const User &I) { visitBinary(I, ISD::UREM); }
void visitSRem(const User &I) { visitBinary(I, ISD::SREM); }
void visitFRem(const User &I) { visitBinary(I, ISD::FREM); }
void visitUDiv(const User &I) { visitBinary(I, ISD::UDIV); }
void visitSDiv(const User &I);
void visitFDiv(const User &I) { visitBinary(I, ISD::FDIV); }
void visitAnd (const User &I) { visitBinary(I, ISD::AND); }
void visitOr (const User &I) { visitBinary(I, ISD::OR); }
void visitXor (const User &I) { visitBinary(I, ISD::XOR); }
void visitShl (const User &I) { visitShift(I, ISD::SHL); }
void visitLShr(const User &I) { visitShift(I, ISD::SRL); }
void visitAShr(const User &I) { visitShift(I, ISD::SRA); }
void visitICmp(const User &I);
void visitFCmp(const User &I);
// Visit the conversion instructions
void visitTrunc(const User &I);
void visitZExt(const User &I);
void visitSExt(const User &I);
void visitFPTrunc(const User &I);
void visitFPExt(const User &I);
void visitFPToUI(const User &I);
void visitFPToSI(const User &I);
void visitUIToFP(const User &I);
void visitSIToFP(const User &I);
void visitPtrToInt(const User &I);
void visitIntToPtr(const User &I);
void visitBitCast(const User &I);
void visitAddrSpaceCast(const User &I);
void visitExtractElement(const User &I);
void visitInsertElement(const User &I);
void visitShuffleVector(const User &I);
void visitExtractValue(const User &I);
void visitInsertValue(const User &I);
void visitLandingPad(const LandingPadInst &LP);
void visitGetElementPtr(const User &I);
void visitSelect(const User &I);
void visitAlloca(const AllocaInst &I);
void visitLoad(const LoadInst &I);
void visitStore(const StoreInst &I);
void visitMaskedLoad(const CallInst &I, bool IsExpanding = false);
void visitMaskedStore(const CallInst &I, bool IsCompressing = false);
void visitMaskedGather(const CallInst &I);
void visitMaskedScatter(const CallInst &I);
void visitAtomicCmpXchg(const AtomicCmpXchgInst &I);
void visitAtomicRMW(const AtomicRMWInst &I);
void visitFence(const FenceInst &I);
void visitPHI(const PHINode &I);
void visitCall(const CallInst &I);
bool visitMemCmpCall(const CallInst &I);
bool visitMemPCpyCall(const CallInst &I);
bool visitMemChrCall(const CallInst &I);
bool visitStrCpyCall(const CallInst &I, bool isStpcpy);
bool visitStrCmpCall(const CallInst &I);
bool visitStrLenCall(const CallInst &I);
bool visitStrNLenCall(const CallInst &I);
bool visitUnaryFloatCall(const CallInst &I, unsigned Opcode);
bool visitBinaryFloatCall(const CallInst &I, unsigned Opcode);
void visitAtomicLoad(const LoadInst &I);
void visitAtomicStore(const StoreInst &I);
void visitLoadFromSwiftError(const LoadInst &I);
void visitStoreToSwiftError(const StoreInst &I);
void visitInlineAsm(ImmutableCallSite CS);
const char *visitIntrinsicCall(const CallInst &I, unsigned Intrinsic);
void visitTargetIntrinsic(const CallInst &I, unsigned Intrinsic);
void visitConstrainedFPIntrinsic(const ConstrainedFPIntrinsic &FPI);
void visitVAStart(const CallInst &I);
void visitVAArg(const VAArgInst &I);
void visitVAEnd(const CallInst &I);
void visitVACopy(const CallInst &I);
void visitStackmap(const CallInst &I);
void visitPatchpoint(ImmutableCallSite CS,
const BasicBlock *EHPadBB = nullptr);
// These two are implemented in StatepointLowering.cpp
void visitGCRelocate(const GCRelocateInst &Relocate);
void visitGCResult(const GCResultInst &I);
void visitVectorReduce(const CallInst &I, unsigned Intrinsic);
void visitUserOp1(const Instruction &I) {
llvm_unreachable("UserOp1 should not exist at instruction selection time!");
void visitUserOp2(const Instruction &I) {
llvm_unreachable("UserOp2 should not exist at instruction selection time!");
void processIntegerCallValue(const Instruction &I,
SDValue Value, bool IsSigned);
void HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB);
void emitInlineAsmError(ImmutableCallSite CS, const Twine &Message);
/// If V is an function argument then create corresponding DBG_VALUE machine
/// instruction for it now. At the end of instruction selection, they will be
/// inserted to the entry BB.
bool EmitFuncArgumentDbgValue(const Value *V, DILocalVariable *Variable,
DIExpression *Expr, DILocation *DL,
bool IsDbgDeclare, const SDValue &N);
/// Return the next block after MBB, or nullptr if there is none.
MachineBasicBlock *NextBlock(MachineBasicBlock *MBB);
/// Update the DAG and DAG builder with the relevant information after
/// a new root node has been created which could be a tail call.
void updateDAGForMaybeTailCall(SDValue MaybeTC);
/// Return the appropriate SDDbgValue based on N.
SDDbgValue *getDbgValue(SDValue N, DILocalVariable *Variable,
DIExpression *Expr, const DebugLoc &dl,
unsigned DbgSDNodeOrder);
/// RegsForValue - This struct represents the registers (physical or virtual)
/// that a particular set of values is assigned, and the type information about
/// the value. The most common situation is to represent one value at a time,
/// but struct or array values are handled element-wise as multiple values. The
/// splitting of aggregates is performed recursively, so that we never have
/// aggregate-typed registers. The values at this point do not necessarily have
/// legal types, so each value may require one or more registers of some legal
/// type.
struct RegsForValue {
/// The value types of the values, which may not be legal, and
/// may need be promoted or synthesized from one or more registers.
SmallVector<EVT, 4> ValueVTs;
/// The value types of the registers. This is the same size as ValueVTs and it
/// records, for each value, what the type of the assigned register or
/// registers are. (Individual values are never synthesized from more than one
/// type of register.)
/// With virtual registers, the contents of RegVTs is redundant with TLI's
/// getRegisterType member function, however when with physical registers
/// it is necessary to have a separate record of the types.
SmallVector<MVT, 4> RegVTs;
/// This list holds the registers assigned to the values.
/// Each legal or promoted value requires one register, and each
/// expanded value requires multiple registers.
SmallVector<unsigned, 4> Regs;
/// This list holds the number of registers for each value.
SmallVector<unsigned, 4> RegCount;
/// Records if this value needs to be treated in an ABI dependant manner,
/// different to normal type legalization.
Optional<CallingConv::ID> CallConv;
RegsForValue() = default;
RegsForValue(const SmallVector<unsigned, 4> &regs, MVT regvt, EVT valuevt,
Optional<CallingConv::ID> CC = None);
RegsForValue(LLVMContext &Context, const TargetLowering &TLI,
const DataLayout &DL, unsigned Reg, Type *Ty,
Optional<CallingConv::ID> CC);
bool isABIMangled() const {
return CallConv.hasValue();
/// Add the specified values to this one.
void append(const RegsForValue &RHS) {
ValueVTs.append(RHS.ValueVTs.begin(), RHS.ValueVTs.end());
RegVTs.append(RHS.RegVTs.begin(), RHS.RegVTs.end());
Regs.append(RHS.Regs.begin(), RHS.Regs.end());
/// Emit a series of CopyFromReg nodes that copies from this value and returns
/// the result as a ValueVTs value. This uses Chain/Flag as the input and
/// updates them for the output Chain/Flag. If the Flag pointer is NULL, no
/// flag is used.
SDValue getCopyFromRegs(SelectionDAG &DAG, FunctionLoweringInfo &FuncInfo,
const SDLoc &dl, SDValue &Chain, SDValue *Flag,
const Value *V = nullptr) const;
/// Emit a series of CopyToReg nodes that copies the specified value into the
/// registers specified by this object. This uses Chain/Flag as the input and
/// updates them for the output Chain/Flag. If the Flag pointer is nullptr, no
/// flag is used. If V is not nullptr, then it is used in printing better
/// diagnostic messages on error.
void getCopyToRegs(SDValue Val, SelectionDAG &DAG, const SDLoc &dl,
SDValue &Chain, SDValue *Flag, const Value *V = nullptr,
ISD::NodeType PreferredExtendType = ISD::ANY_EXTEND) const;
/// Add this value to the specified inlineasm node operand list. This adds the
/// code marker, matching input operand index (if applicable), and includes
/// the number of values added into it.
void AddInlineAsmOperands(unsigned Code, bool HasMatching,
unsigned MatchingIdx, const SDLoc &dl,
SelectionDAG &DAG, std::vector<SDValue> &Ops) const;
/// Check if the total RegCount is greater than one.
bool occupiesMultipleRegs() const {
return std::accumulate(RegCount.begin(), RegCount.end(), 0) > 1;
/// Return a list of registers and their sizes.
SmallVector<std::pair<unsigned, unsigned>, 4> getRegsAndSizes() const;
} // end namespace llvm