371 lines
14 KiB
C++
371 lines
14 KiB
C++
//===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines several CodeGen-specific LLVM IR analysis utilties.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Analysis.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Module.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/SelectionDAG.h"
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#include "llvm/DataLayout.h"
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#include "llvm/Target/TargetLowering.h"
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#include "llvm/Target/TargetOptions.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/MathExtras.h"
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using namespace llvm;
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/// ComputeLinearIndex - Given an LLVM IR aggregate type and a sequence
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/// of insertvalue or extractvalue indices that identify a member, return
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/// the linearized index of the start of the member.
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///
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unsigned llvm::ComputeLinearIndex(Type *Ty,
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const unsigned *Indices,
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const unsigned *IndicesEnd,
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unsigned CurIndex) {
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// Base case: We're done.
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if (Indices && Indices == IndicesEnd)
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return CurIndex;
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// Given a struct type, recursively traverse the elements.
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if (StructType *STy = dyn_cast<StructType>(Ty)) {
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for (StructType::element_iterator EB = STy->element_begin(),
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EI = EB,
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EE = STy->element_end();
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EI != EE; ++EI) {
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if (Indices && *Indices == unsigned(EI - EB))
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return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
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CurIndex = ComputeLinearIndex(*EI, 0, 0, CurIndex);
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}
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return CurIndex;
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}
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// Given an array type, recursively traverse the elements.
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else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
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Type *EltTy = ATy->getElementType();
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for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i) {
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if (Indices && *Indices == i)
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return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
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CurIndex = ComputeLinearIndex(EltTy, 0, 0, CurIndex);
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}
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return CurIndex;
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}
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// We haven't found the type we're looking for, so keep searching.
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return CurIndex + 1;
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}
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/// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
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/// EVTs that represent all the individual underlying
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/// non-aggregate types that comprise it.
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///
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/// If Offsets is non-null, it points to a vector to be filled in
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/// with the in-memory offsets of each of the individual values.
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///
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void llvm::ComputeValueVTs(const TargetLowering &TLI, Type *Ty,
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SmallVectorImpl<EVT> &ValueVTs,
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SmallVectorImpl<uint64_t> *Offsets,
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uint64_t StartingOffset) {
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// Given a struct type, recursively traverse the elements.
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if (StructType *STy = dyn_cast<StructType>(Ty)) {
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const StructLayout *SL = TLI.getDataLayout()->getStructLayout(STy);
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for (StructType::element_iterator EB = STy->element_begin(),
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EI = EB,
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EE = STy->element_end();
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EI != EE; ++EI)
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ComputeValueVTs(TLI, *EI, ValueVTs, Offsets,
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StartingOffset + SL->getElementOffset(EI - EB));
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return;
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}
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// Given an array type, recursively traverse the elements.
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if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
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Type *EltTy = ATy->getElementType();
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uint64_t EltSize = TLI.getDataLayout()->getTypeAllocSize(EltTy);
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for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
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ComputeValueVTs(TLI, EltTy, ValueVTs, Offsets,
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StartingOffset + i * EltSize);
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return;
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}
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// Interpret void as zero return values.
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if (Ty->isVoidTy())
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return;
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// Base case: we can get an EVT for this LLVM IR type.
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ValueVTs.push_back(TLI.getValueType(Ty));
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if (Offsets)
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Offsets->push_back(StartingOffset);
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}
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/// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
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GlobalVariable *llvm::ExtractTypeInfo(Value *V) {
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V = V->stripPointerCasts();
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GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
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if (GV && GV->getName() == "llvm.eh.catch.all.value") {
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assert(GV->hasInitializer() &&
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"The EH catch-all value must have an initializer");
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Value *Init = GV->getInitializer();
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GV = dyn_cast<GlobalVariable>(Init);
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if (!GV) V = cast<ConstantPointerNull>(Init);
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}
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assert((GV || isa<ConstantPointerNull>(V)) &&
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"TypeInfo must be a global variable or NULL");
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return GV;
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}
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/// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
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/// processed uses a memory 'm' constraint.
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bool
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llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
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const TargetLowering &TLI) {
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for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
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InlineAsm::ConstraintInfo &CI = CInfos[i];
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for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
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TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
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if (CType == TargetLowering::C_Memory)
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return true;
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}
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// Indirect operand accesses access memory.
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if (CI.isIndirect)
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return true;
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}
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return false;
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}
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/// getFCmpCondCode - Return the ISD condition code corresponding to
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/// the given LLVM IR floating-point condition code. This includes
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/// consideration of global floating-point math flags.
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///
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ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
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switch (Pred) {
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case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
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case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
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case FCmpInst::FCMP_OGT: return ISD::SETOGT;
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case FCmpInst::FCMP_OGE: return ISD::SETOGE;
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case FCmpInst::FCMP_OLT: return ISD::SETOLT;
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case FCmpInst::FCMP_OLE: return ISD::SETOLE;
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case FCmpInst::FCMP_ONE: return ISD::SETONE;
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case FCmpInst::FCMP_ORD: return ISD::SETO;
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case FCmpInst::FCMP_UNO: return ISD::SETUO;
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case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
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case FCmpInst::FCMP_UGT: return ISD::SETUGT;
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case FCmpInst::FCMP_UGE: return ISD::SETUGE;
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case FCmpInst::FCMP_ULT: return ISD::SETULT;
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case FCmpInst::FCMP_ULE: return ISD::SETULE;
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case FCmpInst::FCMP_UNE: return ISD::SETUNE;
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case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
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default: llvm_unreachable("Invalid FCmp predicate opcode!");
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}
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}
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ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
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switch (CC) {
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case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
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case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
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case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
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case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
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case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
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case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
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default: return CC;
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}
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}
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/// getICmpCondCode - Return the ISD condition code corresponding to
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/// the given LLVM IR integer condition code.
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///
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ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
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switch (Pred) {
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case ICmpInst::ICMP_EQ: return ISD::SETEQ;
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case ICmpInst::ICMP_NE: return ISD::SETNE;
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case ICmpInst::ICMP_SLE: return ISD::SETLE;
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case ICmpInst::ICMP_ULE: return ISD::SETULE;
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case ICmpInst::ICMP_SGE: return ISD::SETGE;
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case ICmpInst::ICMP_UGE: return ISD::SETUGE;
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case ICmpInst::ICMP_SLT: return ISD::SETLT;
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case ICmpInst::ICMP_ULT: return ISD::SETULT;
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case ICmpInst::ICMP_SGT: return ISD::SETGT;
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case ICmpInst::ICMP_UGT: return ISD::SETUGT;
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default:
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llvm_unreachable("Invalid ICmp predicate opcode!");
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}
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}
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/// getNoopInput - If V is a noop (i.e., lowers to no machine code), look
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/// through it (and any transitive noop operands to it) and return its input
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/// value. This is used to determine if a tail call can be formed.
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///
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static const Value *getNoopInput(const Value *V, const TargetLowering &TLI) {
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// If V is not an instruction, it can't be looked through.
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const Instruction *I = dyn_cast<Instruction>(V);
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if (I == 0 || !I->hasOneUse() || I->getNumOperands() == 0) return V;
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Value *Op = I->getOperand(0);
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// Look through truly no-op truncates.
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if (isa<TruncInst>(I) &&
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TLI.isTruncateFree(I->getOperand(0)->getType(), I->getType()))
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return getNoopInput(I->getOperand(0), TLI);
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// Look through truly no-op bitcasts.
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if (isa<BitCastInst>(I)) {
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// No type change at all.
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if (Op->getType() == I->getType())
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return getNoopInput(Op, TLI);
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// Pointer to pointer cast.
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if (Op->getType()->isPointerTy() && I->getType()->isPointerTy())
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return getNoopInput(Op, TLI);
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if (isa<VectorType>(Op->getType()) && isa<VectorType>(I->getType()) &&
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TLI.isTypeLegal(EVT::getEVT(Op->getType())) &&
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TLI.isTypeLegal(EVT::getEVT(I->getType())))
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return getNoopInput(Op, TLI);
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}
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// Look through inttoptr.
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if (isa<IntToPtrInst>(I) && !isa<VectorType>(I->getType())) {
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// Make sure this isn't a truncating or extending cast. We could support
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// this eventually, but don't bother for now.
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if (TLI.getPointerTy().getSizeInBits() ==
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cast<IntegerType>(Op->getType())->getBitWidth())
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return getNoopInput(Op, TLI);
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}
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// Look through ptrtoint.
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if (isa<PtrToIntInst>(I) && !isa<VectorType>(I->getType())) {
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// Make sure this isn't a truncating or extending cast. We could support
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// this eventually, but don't bother for now.
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if (TLI.getPointerTy().getSizeInBits() ==
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cast<IntegerType>(I->getType())->getBitWidth())
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return getNoopInput(Op, TLI);
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}
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// Otherwise it's not something we can look through.
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return V;
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}
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/// Test if the given instruction is in a position to be optimized
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/// with a tail-call. This roughly means that it's in a block with
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/// a return and there's nothing that needs to be scheduled
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/// between it and the return.
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///
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/// This function only tests target-independent requirements.
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bool llvm::isInTailCallPosition(ImmutableCallSite CS, Attributes CalleeRetAttr,
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const TargetLowering &TLI) {
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const Instruction *I = CS.getInstruction();
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const BasicBlock *ExitBB = I->getParent();
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const TerminatorInst *Term = ExitBB->getTerminator();
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const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
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// The block must end in a return statement or unreachable.
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//
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// FIXME: Decline tailcall if it's not guaranteed and if the block ends in
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// an unreachable, for now. The way tailcall optimization is currently
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// implemented means it will add an epilogue followed by a jump. That is
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// not profitable. Also, if the callee is a special function (e.g.
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// longjmp on x86), it can end up causing miscompilation that has not
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// been fully understood.
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if (!Ret &&
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(!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
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!isa<UnreachableInst>(Term)))
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return false;
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// If I will have a chain, make sure no other instruction that will have a
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// chain interposes between I and the return.
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if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
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!isSafeToSpeculativelyExecute(I))
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for (BasicBlock::const_iterator BBI = prior(prior(ExitBB->end())); ;
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--BBI) {
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if (&*BBI == I)
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break;
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// Debug info intrinsics do not get in the way of tail call optimization.
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if (isa<DbgInfoIntrinsic>(BBI))
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continue;
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if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
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!isSafeToSpeculativelyExecute(BBI))
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return false;
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}
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// If the block ends with a void return or unreachable, it doesn't matter
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// what the call's return type is.
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if (!Ret || Ret->getNumOperands() == 0) return true;
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// If the return value is undef, it doesn't matter what the call's
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// return type is.
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if (isa<UndefValue>(Ret->getOperand(0))) return true;
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// Conservatively require the attributes of the call to match those of
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// the return. Ignore noalias because it doesn't affect the call sequence.
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const Function *F = ExitBB->getParent();
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Attributes CallerRetAttr = F->getAttributes().getRetAttributes();
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if (AttrBuilder(CalleeRetAttr).removeAttribute(Attributes::NoAlias) !=
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AttrBuilder(CallerRetAttr).removeAttribute(Attributes::NoAlias))
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return false;
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// It's not safe to eliminate the sign / zero extension of the return value.
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if (CallerRetAttr.hasAttribute(Attributes::ZExt) ||
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CallerRetAttr.hasAttribute(Attributes::SExt))
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return false;
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// Otherwise, make sure the unmodified return value of I is the return value.
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// We handle two cases: multiple return values + scalars.
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Value *RetVal = Ret->getOperand(0);
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if (!isa<InsertValueInst>(RetVal) || !isa<StructType>(RetVal->getType()))
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// Handle scalars first.
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return getNoopInput(Ret->getOperand(0), TLI) == I;
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// If this is an aggregate return, look through the insert/extract values and
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// see if each is transparent.
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for (unsigned i = 0, e =cast<StructType>(RetVal->getType())->getNumElements();
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i != e; ++i) {
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const Value *InScalar = FindInsertedValue(RetVal, i);
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if (InScalar == 0) return false;
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InScalar = getNoopInput(InScalar, TLI);
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// If the scalar value being inserted is an extractvalue of the right index
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// from the call, then everything is good.
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const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(InScalar);
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if (EVI == 0 || EVI->getOperand(0) != I || EVI->getNumIndices() != 1 ||
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EVI->getIndices()[0] != i)
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return false;
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}
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return true;
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}
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bool llvm::isInTailCallPosition(SelectionDAG &DAG, SDNode *Node,
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SDValue &Chain, const TargetLowering &TLI) {
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const Function *F = DAG.getMachineFunction().getFunction();
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// Conservatively require the attributes of the call to match those of
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// the return. Ignore noalias because it doesn't affect the call sequence.
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Attributes CallerRetAttr = F->getAttributes().getRetAttributes();
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if (AttrBuilder(CallerRetAttr)
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.removeAttribute(Attributes::NoAlias).hasAttributes())
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return false;
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// It's not safe to eliminate the sign / zero extension of the return value.
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if (CallerRetAttr.hasAttribute(Attributes::ZExt) ||
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CallerRetAttr.hasAttribute(Attributes::SExt))
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return false;
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// Check if the only use is a function return node.
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return TLI.isUsedByReturnOnly(Node, Chain);
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}
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