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609 lines
24 KiB
C++
609 lines
24 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/CodeGen/MachineFunction.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Target/TargetLowering.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, nullptr, nullptr, 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, nullptr, nullptr, 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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static bool isNoopBitcast(Type *T1, Type *T2,
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const TargetLoweringBase& TLI) {
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return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) ||
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(isa<VectorType>(T1) && isa<VectorType>(T2) &&
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TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2)));
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}
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/// Look through operations that will be free to find the earliest source of
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/// this value.
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///
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/// @param ValLoc If V has aggegate type, we will be interested in a particular
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/// scalar component. This records its address; the reverse of this list gives a
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/// sequence of indices appropriate for an extractvalue to locate the important
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/// value. This value is updated during the function and on exit will indicate
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/// similar information for the Value returned.
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///
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/// @param DataBits If this function looks through truncate instructions, this
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/// will record the smallest size attained.
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static const Value *getNoopInput(const Value *V,
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SmallVectorImpl<unsigned> &ValLoc,
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unsigned &DataBits,
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const TargetLoweringBase &TLI) {
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while (true) {
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// Try to look through V1; if V1 is not an instruction, it can't be looked
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// through.
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const Instruction *I = dyn_cast<Instruction>(V);
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if (!I || I->getNumOperands() == 0) return V;
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const Value *NoopInput = nullptr;
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Value *Op = I->getOperand(0);
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if (isa<BitCastInst>(I)) {
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// Look through truly no-op bitcasts.
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if (isNoopBitcast(Op->getType(), I->getType(), TLI))
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NoopInput = Op;
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} else if (isa<GetElementPtrInst>(I)) {
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// Look through getelementptr
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if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
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NoopInput = Op;
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} else if (isa<IntToPtrInst>(I)) {
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// Look through inttoptr.
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// Make sure this isn't a truncating or extending cast. We could
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// support this eventually, but don't bother for now.
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if (!isa<VectorType>(I->getType()) &&
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TLI.getPointerTy().getSizeInBits() ==
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cast<IntegerType>(Op->getType())->getBitWidth())
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NoopInput = Op;
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} else if (isa<PtrToIntInst>(I)) {
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// Look through ptrtoint.
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// Make sure this isn't a truncating or extending cast. We could
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// support this eventually, but don't bother for now.
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if (!isa<VectorType>(I->getType()) &&
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TLI.getPointerTy().getSizeInBits() ==
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cast<IntegerType>(I->getType())->getBitWidth())
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NoopInput = Op;
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} else if (isa<TruncInst>(I) &&
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TLI.allowTruncateForTailCall(Op->getType(), I->getType())) {
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DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits());
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NoopInput = Op;
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} else if (isa<CallInst>(I)) {
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// Look through call (skipping callee)
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for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 1;
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i != e; ++i) {
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unsigned attrInd = i - I->op_begin() + 1;
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if (cast<CallInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
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isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
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NoopInput = *i;
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break;
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}
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}
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} else if (isa<InvokeInst>(I)) {
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// Look through invoke (skipping BB, BB, Callee)
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for (User::const_op_iterator i = I->op_begin(), e = I->op_end() - 3;
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i != e; ++i) {
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unsigned attrInd = i - I->op_begin() + 1;
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if (cast<InvokeInst>(I)->paramHasAttr(attrInd, Attribute::Returned) &&
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isNoopBitcast((*i)->getType(), I->getType(), TLI)) {
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NoopInput = *i;
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break;
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}
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}
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} else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(V)) {
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// Value may come from either the aggregate or the scalar
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ArrayRef<unsigned> InsertLoc = IVI->getIndices();
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if (std::equal(InsertLoc.rbegin(), InsertLoc.rend(),
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ValLoc.rbegin())) {
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// The type being inserted is a nested sub-type of the aggregate; we
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// have to remove those initial indices to get the location we're
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// interested in for the operand.
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ValLoc.resize(ValLoc.size() - InsertLoc.size());
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NoopInput = IVI->getInsertedValueOperand();
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} else {
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// The struct we're inserting into has the value we're interested in, no
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// change of address.
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NoopInput = Op;
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}
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} else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
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// The part we're interested in will inevitably be some sub-section of the
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// previous aggregate. Combine the two paths to obtain the true address of
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// our element.
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ArrayRef<unsigned> ExtractLoc = EVI->getIndices();
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std::copy(ExtractLoc.rbegin(), ExtractLoc.rend(),
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std::back_inserter(ValLoc));
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NoopInput = Op;
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}
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// Terminate if we couldn't find anything to look through.
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if (!NoopInput)
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return V;
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V = NoopInput;
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}
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}
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/// Return true if this scalar return value only has bits discarded on its path
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/// from the "tail call" to the "ret". This includes the obvious noop
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/// instructions handled by getNoopInput above as well as free truncations (or
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/// extensions prior to the call).
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static bool slotOnlyDiscardsData(const Value *RetVal, const Value *CallVal,
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SmallVectorImpl<unsigned> &RetIndices,
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SmallVectorImpl<unsigned> &CallIndices,
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bool AllowDifferingSizes,
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const TargetLoweringBase &TLI) {
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// Trace the sub-value needed by the return value as far back up the graph as
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// possible, in the hope that it will intersect with the value produced by the
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// call. In the simple case with no "returned" attribute, the hope is actually
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// that we end up back at the tail call instruction itself.
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unsigned BitsRequired = UINT_MAX;
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RetVal = getNoopInput(RetVal, RetIndices, BitsRequired, TLI);
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// If this slot in the value returned is undef, it doesn't matter what the
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// call puts there, it'll be fine.
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if (isa<UndefValue>(RetVal))
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return true;
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// Now do a similar search up through the graph to find where the value
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// actually returned by the "tail call" comes from. In the simple case without
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// a "returned" attribute, the search will be blocked immediately and the loop
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// a Noop.
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unsigned BitsProvided = UINT_MAX;
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CallVal = getNoopInput(CallVal, CallIndices, BitsProvided, TLI);
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// There's no hope if we can't actually trace them to (the same part of!) the
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// same value.
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if (CallVal != RetVal || CallIndices != RetIndices)
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return false;
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// However, intervening truncates may have made the call non-tail. Make sure
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// all the bits that are needed by the "ret" have been provided by the "tail
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// call". FIXME: with sufficiently cunning bit-tracking, we could look through
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// extensions too.
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if (BitsProvided < BitsRequired ||
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(!AllowDifferingSizes && BitsProvided != BitsRequired))
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return false;
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return true;
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}
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/// For an aggregate type, determine whether a given index is within bounds or
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/// not.
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static bool indexReallyValid(CompositeType *T, unsigned Idx) {
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if (ArrayType *AT = dyn_cast<ArrayType>(T))
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return Idx < AT->getNumElements();
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return Idx < cast<StructType>(T)->getNumElements();
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}
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/// Move the given iterators to the next leaf type in depth first traversal.
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///
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/// Performs a depth-first traversal of the type as specified by its arguments,
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/// stopping at the next leaf node (which may be a legitimate scalar type or an
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/// empty struct or array).
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///
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/// @param SubTypes List of the partial components making up the type from
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/// outermost to innermost non-empty aggregate. The element currently
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/// represented is SubTypes.back()->getTypeAtIndex(Path.back() - 1).
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///
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/// @param Path Set of extractvalue indices leading from the outermost type
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/// (SubTypes[0]) to the leaf node currently represented.
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///
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/// @returns true if a new type was found, false otherwise. Calling this
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/// function again on a finished iterator will repeatedly return
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/// false. SubTypes.back()->getTypeAtIndex(Path.back()) is either an empty
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/// aggregate or a non-aggregate
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static bool advanceToNextLeafType(SmallVectorImpl<CompositeType *> &SubTypes,
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SmallVectorImpl<unsigned> &Path) {
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// First march back up the tree until we can successfully increment one of the
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// coordinates in Path.
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while (!Path.empty() && !indexReallyValid(SubTypes.back(), Path.back() + 1)) {
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Path.pop_back();
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SubTypes.pop_back();
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}
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// If we reached the top, then the iterator is done.
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if (Path.empty())
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return false;
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// We know there's *some* valid leaf now, so march back down the tree picking
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// out the left-most element at each node.
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++Path.back();
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Type *DeeperType = SubTypes.back()->getTypeAtIndex(Path.back());
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while (DeeperType->isAggregateType()) {
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CompositeType *CT = cast<CompositeType>(DeeperType);
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if (!indexReallyValid(CT, 0))
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return true;
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SubTypes.push_back(CT);
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Path.push_back(0);
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DeeperType = CT->getTypeAtIndex(0U);
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}
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return true;
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}
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/// Find the first non-empty, scalar-like type in Next and setup the iterator
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/// components.
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///
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/// Assuming Next is an aggregate of some kind, this function will traverse the
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/// tree from left to right (i.e. depth-first) looking for the first
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/// non-aggregate type which will play a role in function return.
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///
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/// For example, if Next was {[0 x i64], {{}, i32, {}}, i32} then we would setup
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/// Path as [1, 1] and SubTypes as [Next, {{}, i32, {}}] to represent the first
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/// i32 in that type.
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static bool firstRealType(Type *Next,
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SmallVectorImpl<CompositeType *> &SubTypes,
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SmallVectorImpl<unsigned> &Path) {
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// First initialise the iterator components to the first "leaf" node
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// (i.e. node with no valid sub-type at any index, so {} does count as a leaf
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// despite nominally being an aggregate).
|
|
while (Next->isAggregateType() &&
|
|
indexReallyValid(cast<CompositeType>(Next), 0)) {
|
|
SubTypes.push_back(cast<CompositeType>(Next));
|
|
Path.push_back(0);
|
|
Next = cast<CompositeType>(Next)->getTypeAtIndex(0U);
|
|
}
|
|
|
|
// If there's no Path now, Next was originally scalar already (or empty
|
|
// leaf). We're done.
|
|
if (Path.empty())
|
|
return true;
|
|
|
|
// Otherwise, use normal iteration to keep looking through the tree until we
|
|
// find a non-aggregate type.
|
|
while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()) {
|
|
if (!advanceToNextLeafType(SubTypes, Path))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/// Set the iterator data-structures to the next non-empty, non-aggregate
|
|
/// subtype.
|
|
static bool nextRealType(SmallVectorImpl<CompositeType *> &SubTypes,
|
|
SmallVectorImpl<unsigned> &Path) {
|
|
do {
|
|
if (!advanceToNextLeafType(SubTypes, Path))
|
|
return false;
|
|
|
|
assert(!Path.empty() && "found a leaf but didn't set the path?");
|
|
} while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType());
|
|
|
|
return true;
|
|
}
|
|
|
|
|
|
/// Test if the given instruction is in a position to be optimized
|
|
/// with a tail-call. This roughly means that it's in a block with
|
|
/// a return and there's nothing that needs to be scheduled
|
|
/// between it and the return.
|
|
///
|
|
/// This function only tests target-independent requirements.
|
|
bool llvm::isInTailCallPosition(ImmutableCallSite CS,
|
|
const TargetLowering &TLI) {
|
|
const Instruction *I = CS.getInstruction();
|
|
const BasicBlock *ExitBB = I->getParent();
|
|
const TerminatorInst *Term = ExitBB->getTerminator();
|
|
const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
|
|
|
|
// The block must end in a return statement or unreachable.
|
|
//
|
|
// FIXME: Decline tailcall if it's not guaranteed and if the block ends in
|
|
// an unreachable, for now. The way tailcall optimization is currently
|
|
// implemented means it will add an epilogue followed by a jump. That is
|
|
// not profitable. Also, if the callee is a special function (e.g.
|
|
// longjmp on x86), it can end up causing miscompilation that has not
|
|
// been fully understood.
|
|
if (!Ret &&
|
|
(!TLI.getTargetMachine().Options.GuaranteedTailCallOpt ||
|
|
!isa<UnreachableInst>(Term)))
|
|
return false;
|
|
|
|
// If I will have a chain, make sure no other instruction that will have a
|
|
// chain interposes between I and the return.
|
|
if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
|
|
!isSafeToSpeculativelyExecute(I))
|
|
for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
|
|
if (&*BBI == I)
|
|
break;
|
|
// Debug info intrinsics do not get in the way of tail call optimization.
|
|
if (isa<DbgInfoIntrinsic>(BBI))
|
|
continue;
|
|
if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
|
|
!isSafeToSpeculativelyExecute(BBI))
|
|
return false;
|
|
}
|
|
|
|
return returnTypeIsEligibleForTailCall(ExitBB->getParent(), I, Ret, TLI);
|
|
}
|
|
|
|
bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
|
|
const Instruction *I,
|
|
const ReturnInst *Ret,
|
|
const TargetLoweringBase &TLI) {
|
|
// If the block ends with a void return or unreachable, it doesn't matter
|
|
// what the call's return type is.
|
|
if (!Ret || Ret->getNumOperands() == 0) return true;
|
|
|
|
// If the return value is undef, it doesn't matter what the call's
|
|
// return type is.
|
|
if (isa<UndefValue>(Ret->getOperand(0))) return true;
|
|
|
|
// Make sure the attributes attached to each return are compatible.
|
|
AttrBuilder CallerAttrs(F->getAttributes(),
|
|
AttributeSet::ReturnIndex);
|
|
AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
|
|
AttributeSet::ReturnIndex);
|
|
|
|
// Noalias is completely benign as far as calling convention goes, it
|
|
// shouldn't affect whether the call is a tail call.
|
|
CallerAttrs = CallerAttrs.removeAttribute(Attribute::NoAlias);
|
|
CalleeAttrs = CalleeAttrs.removeAttribute(Attribute::NoAlias);
|
|
|
|
bool AllowDifferingSizes = true;
|
|
if (CallerAttrs.contains(Attribute::ZExt)) {
|
|
if (!CalleeAttrs.contains(Attribute::ZExt))
|
|
return false;
|
|
|
|
AllowDifferingSizes = false;
|
|
CallerAttrs.removeAttribute(Attribute::ZExt);
|
|
CalleeAttrs.removeAttribute(Attribute::ZExt);
|
|
} else if (CallerAttrs.contains(Attribute::SExt)) {
|
|
if (!CalleeAttrs.contains(Attribute::SExt))
|
|
return false;
|
|
|
|
AllowDifferingSizes = false;
|
|
CallerAttrs.removeAttribute(Attribute::SExt);
|
|
CalleeAttrs.removeAttribute(Attribute::SExt);
|
|
}
|
|
|
|
// If they're still different, there's some facet we don't understand
|
|
// (currently only "inreg", but in future who knows). It may be OK but the
|
|
// only safe option is to reject the tail call.
|
|
if (CallerAttrs != CalleeAttrs)
|
|
return false;
|
|
|
|
const Value *RetVal = Ret->getOperand(0), *CallVal = I;
|
|
SmallVector<unsigned, 4> RetPath, CallPath;
|
|
SmallVector<CompositeType *, 4> RetSubTypes, CallSubTypes;
|
|
|
|
bool RetEmpty = !firstRealType(RetVal->getType(), RetSubTypes, RetPath);
|
|
bool CallEmpty = !firstRealType(CallVal->getType(), CallSubTypes, CallPath);
|
|
|
|
// Nothing's actually returned, it doesn't matter what the callee put there
|
|
// it's a valid tail call.
|
|
if (RetEmpty)
|
|
return true;
|
|
|
|
// Iterate pairwise through each of the value types making up the tail call
|
|
// and the corresponding return. For each one we want to know whether it's
|
|
// essentially going directly from the tail call to the ret, via operations
|
|
// that end up not generating any code.
|
|
//
|
|
// We allow a certain amount of covariance here. For example it's permitted
|
|
// for the tail call to define more bits than the ret actually cares about
|
|
// (e.g. via a truncate).
|
|
do {
|
|
if (CallEmpty) {
|
|
// We've exhausted the values produced by the tail call instruction, the
|
|
// rest are essentially undef. The type doesn't really matter, but we need
|
|
// *something*.
|
|
Type *SlotType = RetSubTypes.back()->getTypeAtIndex(RetPath.back());
|
|
CallVal = UndefValue::get(SlotType);
|
|
}
|
|
|
|
// The manipulations performed when we're looking through an insertvalue or
|
|
// an extractvalue would happen at the front of the RetPath list, so since
|
|
// we have to copy it anyway it's more efficient to create a reversed copy.
|
|
using std::copy;
|
|
SmallVector<unsigned, 4> TmpRetPath, TmpCallPath;
|
|
copy(RetPath.rbegin(), RetPath.rend(), std::back_inserter(TmpRetPath));
|
|
copy(CallPath.rbegin(), CallPath.rend(), std::back_inserter(TmpCallPath));
|
|
|
|
// Finally, we can check whether the value produced by the tail call at this
|
|
// index is compatible with the value we return.
|
|
if (!slotOnlyDiscardsData(RetVal, CallVal, TmpRetPath, TmpCallPath,
|
|
AllowDifferingSizes, TLI))
|
|
return false;
|
|
|
|
CallEmpty = !nextRealType(CallSubTypes, CallPath);
|
|
} while(nextRealType(RetSubTypes, RetPath));
|
|
|
|
return true;
|
|
}
|