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//===- CallPromotionUtils.cpp - Utilities for call promotion ----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements utilities useful for promoting indirect call sites to
// direct call sites.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/CallPromotionUtils.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/TypeMetadataUtils.h"
#include "llvm/IR/AttributeMask.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
#define DEBUG_TYPE "call-promotion-utils"
/// Fix-up phi nodes in an invoke instruction's normal destination.
///
/// After versioning an invoke instruction, values coming from the original
/// block will now be coming from the "merge" block. For example, in the code
/// below:
///
/// then_bb:
/// %t0 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
///
/// else_bb:
/// %t1 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
///
/// merge_bb:
/// %t2 = phi i32 [ %t0, %then_bb ], [ %t1, %else_bb ]
/// br %normal_dst
///
/// normal_dst:
/// %t3 = phi i32 [ %x, %orig_bb ], ...
///
/// "orig_bb" is no longer a predecessor of "normal_dst", so the phi nodes in
/// "normal_dst" must be fixed to refer to "merge_bb":
///
/// normal_dst:
/// %t3 = phi i32 [ %x, %merge_bb ], ...
///
static void fixupPHINodeForNormalDest(InvokeInst *Invoke, BasicBlock *OrigBlock,
BasicBlock *MergeBlock) {
for (PHINode &Phi : Invoke->getNormalDest()->phis()) {
int Idx = Phi.getBasicBlockIndex(OrigBlock);
if (Idx == -1)
continue;
Phi.setIncomingBlock(Idx, MergeBlock);
}
}
/// Fix-up phi nodes in an invoke instruction's unwind destination.
///
/// After versioning an invoke instruction, values coming from the original
/// block will now be coming from either the "then" block or the "else" block.
/// For example, in the code below:
///
/// then_bb:
/// %t0 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
///
/// else_bb:
/// %t1 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
///
/// unwind_dst:
/// %t3 = phi i32 [ %x, %orig_bb ], ...
///
/// "orig_bb" is no longer a predecessor of "unwind_dst", so the phi nodes in
/// "unwind_dst" must be fixed to refer to "then_bb" and "else_bb":
///
/// unwind_dst:
/// %t3 = phi i32 [ %x, %then_bb ], [ %x, %else_bb ], ...
///
static void fixupPHINodeForUnwindDest(InvokeInst *Invoke, BasicBlock *OrigBlock,
BasicBlock *ThenBlock,
BasicBlock *ElseBlock) {
for (PHINode &Phi : Invoke->getUnwindDest()->phis()) {
int Idx = Phi.getBasicBlockIndex(OrigBlock);
if (Idx == -1)
continue;
auto *V = Phi.getIncomingValue(Idx);
Phi.setIncomingBlock(Idx, ThenBlock);
Phi.addIncoming(V, ElseBlock);
}
}
/// Create a phi node for the returned value of a call or invoke instruction.
///
/// After versioning a call or invoke instruction that returns a value, we have
/// to merge the value of the original and new instructions. We do this by
/// creating a phi node and replacing uses of the original instruction with this
/// phi node.
///
/// For example, if \p OrigInst is defined in "else_bb" and \p NewInst is
/// defined in "then_bb", we create the following phi node:
///
/// ; Uses of the original instruction are replaced by uses of the phi node.
/// %t0 = phi i32 [ %orig_inst, %else_bb ], [ %new_inst, %then_bb ],
///
static void createRetPHINode(Instruction *OrigInst, Instruction *NewInst,
BasicBlock *MergeBlock, IRBuilder<> &Builder) {
if (OrigInst->getType()->isVoidTy() || OrigInst->use_empty())
return;
Builder.SetInsertPoint(MergeBlock, MergeBlock->begin());
PHINode *Phi = Builder.CreatePHI(OrigInst->getType(), 0);
SmallVector<User *, 16> UsersToUpdate(OrigInst->users());
for (User *U : UsersToUpdate)
U->replaceUsesOfWith(OrigInst, Phi);
Phi->addIncoming(OrigInst, OrigInst->getParent());
Phi->addIncoming(NewInst, NewInst->getParent());
}
/// Cast a call or invoke instruction to the given type.
///
/// When promoting a call site, the return type of the call site might not match
/// that of the callee. If this is the case, we have to cast the returned value
/// to the correct type. The location of the cast depends on if we have a call
/// or invoke instruction.
///
/// For example, if the call instruction below requires a bitcast after
/// promotion:
///
/// orig_bb:
/// %t0 = call i32 @func()
/// ...
///
/// The bitcast is placed after the call instruction:
///
/// orig_bb:
/// ; Uses of the original return value are replaced by uses of the bitcast.
/// %t0 = call i32 @func()
/// %t1 = bitcast i32 %t0 to ...
/// ...
///
/// A similar transformation is performed for invoke instructions. However,
/// since invokes are terminating, a new block is created for the bitcast. For
/// example, if the invoke instruction below requires a bitcast after promotion:
///
/// orig_bb:
/// %t0 = invoke i32 @func() to label %normal_dst unwind label %unwind_dst
///
/// The edge between the original block and the invoke's normal destination is
/// split, and the bitcast is placed there:
///
/// orig_bb:
/// %t0 = invoke i32 @func() to label %split_bb unwind label %unwind_dst
///
/// split_bb:
/// ; Uses of the original return value are replaced by uses of the bitcast.
/// %t1 = bitcast i32 %t0 to ...
/// br label %normal_dst
///
static void createRetBitCast(CallBase &CB, Type *RetTy, CastInst **RetBitCast) {
// Save the users of the calling instruction. These uses will be changed to
// use the bitcast after we create it.
SmallVector<User *, 16> UsersToUpdate(CB.users());
// Determine an appropriate location to create the bitcast for the return
// value. The location depends on if we have a call or invoke instruction.
BasicBlock::iterator InsertBefore;
if (auto *Invoke = dyn_cast<InvokeInst>(&CB))
InsertBefore =
SplitEdge(Invoke->getParent(), Invoke->getNormalDest())->begin();
else
InsertBefore = std::next(CB.getIterator());
// Bitcast the return value to the correct type.
auto *Cast = CastInst::CreateBitOrPointerCast(&CB, RetTy, "", InsertBefore);
if (RetBitCast)
*RetBitCast = Cast;
// Replace all the original uses of the calling instruction with the bitcast.
for (User *U : UsersToUpdate)
U->replaceUsesOfWith(&CB, Cast);
}
/// Predicate and clone the given call site.
///
/// This function creates an if-then-else structure at the location of the call
/// site. The "if" condition is specified by `Cond`.
/// The original call site is moved into the "else" block, and a clone of the
/// call site is placed in the "then" block. The cloned instruction is returned.
///
/// For example, the call instruction below:
///
/// orig_bb:
/// %t0 = call i32 %ptr()
/// ...
///
/// Is replace by the following:
///
/// orig_bb:
/// %cond = Cond
/// br i1 %cond, %then_bb, %else_bb
///
/// then_bb:
/// ; The clone of the original call instruction is placed in the "then"
/// ; block. It is not yet promoted.
/// %t1 = call i32 %ptr()
/// br merge_bb
///
/// else_bb:
/// ; The original call instruction is moved to the "else" block.
/// %t0 = call i32 %ptr()
/// br merge_bb
///
/// merge_bb:
/// ; Uses of the original call instruction are replaced by uses of the phi
/// ; node.
/// %t2 = phi i32 [ %t0, %else_bb ], [ %t1, %then_bb ]
/// ...
///
/// A similar transformation is performed for invoke instructions. However,
/// since invokes are terminating, more work is required. For example, the
/// invoke instruction below:
///
/// orig_bb:
/// %t0 = invoke %ptr() to label %normal_dst unwind label %unwind_dst
///
/// Is replace by the following:
///
/// orig_bb:
/// %cond = Cond
/// br i1 %cond, %then_bb, %else_bb
///
/// then_bb:
/// ; The clone of the original invoke instruction is placed in the "then"
/// ; block, and its normal destination is set to the "merge" block. It is
/// ; not yet promoted.
/// %t1 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
///
/// else_bb:
/// ; The original invoke instruction is moved into the "else" block, and
/// ; its normal destination is set to the "merge" block.
/// %t0 = invoke i32 %ptr() to label %merge_bb unwind label %unwind_dst
///
/// merge_bb:
/// ; Uses of the original invoke instruction are replaced by uses of the
/// ; phi node, and the merge block branches to the normal destination.
/// %t2 = phi i32 [ %t0, %else_bb ], [ %t1, %then_bb ]
/// br %normal_dst
///
/// An indirect musttail call is processed slightly differently in that:
/// 1. No merge block needed for the orginal and the cloned callsite, since
/// either one ends the flow. No phi node is needed either.
/// 2. The return statement following the original call site is duplicated too
/// and placed immediately after the cloned call site per the IR convention.
///
/// For example, the musttail call instruction below:
///
/// orig_bb:
/// %t0 = musttail call i32 %ptr()
/// ...
///
/// Is replaced by the following:
///
/// cond_bb:
/// %cond = Cond
/// br i1 %cond, %then_bb, %orig_bb
///
/// then_bb:
/// ; The clone of the original call instruction is placed in the "then"
/// ; block. It is not yet promoted.
/// %t1 = musttail call i32 %ptr()
/// ret %t1
///
/// orig_bb:
/// ; The original call instruction stays in its original block.
/// %t0 = musttail call i32 %ptr()
/// ret %t0
static CallBase &versionCallSiteWithCond(CallBase &CB, Value *Cond,
MDNode *BranchWeights) {
IRBuilder<> Builder(&CB);
CallBase *OrigInst = &CB;
BasicBlock *OrigBlock = OrigInst->getParent();
if (OrigInst->isMustTailCall()) {
// Create an if-then structure. The original instruction stays in its block,
// and a clone of the original instruction is placed in the "then" block.
Instruction *ThenTerm =
SplitBlockAndInsertIfThen(Cond, &CB, false, BranchWeights);
BasicBlock *ThenBlock = ThenTerm->getParent();
ThenBlock->setName("if.true.direct_targ");
CallBase *NewInst = cast<CallBase>(OrigInst->clone());
NewInst->insertBefore(ThenTerm);
// Place a clone of the optional bitcast after the new call site.
Value *NewRetVal = NewInst;
auto Next = OrigInst->getNextNode();
if (auto *BitCast = dyn_cast_or_null<BitCastInst>(Next)) {
assert(BitCast->getOperand(0) == OrigInst &&
"bitcast following musttail call must use the call");
auto NewBitCast = BitCast->clone();
NewBitCast->replaceUsesOfWith(OrigInst, NewInst);
NewBitCast->insertBefore(ThenTerm);
NewRetVal = NewBitCast;
Next = BitCast->getNextNode();
}
// Place a clone of the return instruction after the new call site.
ReturnInst *Ret = dyn_cast_or_null<ReturnInst>(Next);
assert(Ret && "musttail call must precede a ret with an optional bitcast");
auto NewRet = Ret->clone();
if (Ret->getReturnValue())
NewRet->replaceUsesOfWith(Ret->getReturnValue(), NewRetVal);
NewRet->insertBefore(ThenTerm);
// A return instructions is terminating, so we don't need the terminator
// instruction just created.
ThenTerm->eraseFromParent();
return *NewInst;
}
// Create an if-then-else structure. The original instruction is moved into
// the "else" block, and a clone of the original instruction is placed in the
// "then" block.
Instruction *ThenTerm = nullptr;
Instruction *ElseTerm = nullptr;
SplitBlockAndInsertIfThenElse(Cond, &CB, &ThenTerm, &ElseTerm, BranchWeights);
BasicBlock *ThenBlock = ThenTerm->getParent();
BasicBlock *ElseBlock = ElseTerm->getParent();
BasicBlock *MergeBlock = OrigInst->getParent();
ThenBlock->setName("if.true.direct_targ");
ElseBlock->setName("if.false.orig_indirect");
MergeBlock->setName("if.end.icp");
CallBase *NewInst = cast<CallBase>(OrigInst->clone());
OrigInst->moveBefore(ElseTerm);
NewInst->insertBefore(ThenTerm);
// If the original call site is an invoke instruction, we have extra work to
// do since invoke instructions are terminating. We have to fix-up phi nodes
// in the invoke's normal and unwind destinations.
if (auto *OrigInvoke = dyn_cast<InvokeInst>(OrigInst)) {
auto *NewInvoke = cast<InvokeInst>(NewInst);
// Invoke instructions are terminating, so we don't need the terminator
// instructions that were just created.
ThenTerm->eraseFromParent();
ElseTerm->eraseFromParent();
// Branch from the "merge" block to the original normal destination.
Builder.SetInsertPoint(MergeBlock);
Builder.CreateBr(OrigInvoke->getNormalDest());
// Fix-up phi nodes in the original invoke's normal and unwind destinations.
fixupPHINodeForNormalDest(OrigInvoke, OrigBlock, MergeBlock);
fixupPHINodeForUnwindDest(OrigInvoke, MergeBlock, ThenBlock, ElseBlock);
// Now set the normal destinations of the invoke instructions to be the
// "merge" block.
OrigInvoke->setNormalDest(MergeBlock);
NewInvoke->setNormalDest(MergeBlock);
}
// Create a phi node for the returned value of the call site.
createRetPHINode(OrigInst, NewInst, MergeBlock, Builder);
return *NewInst;
}
// Predicate and clone the given call site using condition `CB.callee ==
// Callee`. See the comment `versionCallSiteWithCond` for the transformation.
CallBase &llvm::versionCallSite(CallBase &CB, Value *Callee,
MDNode *BranchWeights) {
IRBuilder<> Builder(&CB);
// Create the compare. The called value and callee must have the same type to
// be compared.
if (CB.getCalledOperand()->getType() != Callee->getType())
Callee = Builder.CreateBitCast(Callee, CB.getCalledOperand()->getType());
auto *Cond = Builder.CreateICmpEQ(CB.getCalledOperand(), Callee);
return versionCallSiteWithCond(CB, Cond, BranchWeights);
}
bool llvm::isLegalToPromote(const CallBase &CB, Function *Callee,
const char **FailureReason) {
assert(!CB.getCalledFunction() && "Only indirect call sites can be promoted");
auto &DL = Callee->getParent()->getDataLayout();
// Check the return type. The callee's return value type must be bitcast
// compatible with the call site's type.
Type *CallRetTy = CB.getType();
Type *FuncRetTy = Callee->getReturnType();
if (CallRetTy != FuncRetTy)
if (!CastInst::isBitOrNoopPointerCastable(FuncRetTy, CallRetTy, DL)) {
if (FailureReason)
*FailureReason = "Return type mismatch";
return false;
}
// The number of formal arguments of the callee.
unsigned NumParams = Callee->getFunctionType()->getNumParams();
// The number of actual arguments in the call.
unsigned NumArgs = CB.arg_size();
// Check the number of arguments. The callee and call site must agree on the
// number of arguments.
if (NumArgs != NumParams && !Callee->isVarArg()) {
if (FailureReason)
*FailureReason = "The number of arguments mismatch";
return false;
}
// Check the argument types. The callee's formal argument types must be
// bitcast compatible with the corresponding actual argument types of the call
// site.
unsigned I = 0;
for (; I < NumParams; ++I) {
// Make sure that the callee and call agree on byval/inalloca. The types do
// not have to match.
if (Callee->hasParamAttribute(I, Attribute::ByVal) !=
CB.getAttributes().hasParamAttr(I, Attribute::ByVal)) {
if (FailureReason)
*FailureReason = "byval mismatch";
return false;
}
if (Callee->hasParamAttribute(I, Attribute::InAlloca) !=
CB.getAttributes().hasParamAttr(I, Attribute::InAlloca)) {
if (FailureReason)
*FailureReason = "inalloca mismatch";
return false;
}
Type *FormalTy = Callee->getFunctionType()->getFunctionParamType(I);
Type *ActualTy = CB.getArgOperand(I)->getType();
if (FormalTy == ActualTy)
continue;
if (!CastInst::isBitOrNoopPointerCastable(ActualTy, FormalTy, DL)) {
if (FailureReason)
*FailureReason = "Argument type mismatch";
return false;
}
// MustTail call needs stricter type match. See
// Verifier::verifyMustTailCall().
if (CB.isMustTailCall()) {
PointerType *PF = dyn_cast<PointerType>(FormalTy);
PointerType *PA = dyn_cast<PointerType>(ActualTy);
if (!PF || !PA || PF->getAddressSpace() != PA->getAddressSpace()) {
if (FailureReason)
*FailureReason = "Musttail call Argument type mismatch";
return false;
}
}
}
for (; I < NumArgs; I++) {
// Vararg functions can have more arguments than parameters.
assert(Callee->isVarArg());
if (CB.paramHasAttr(I, Attribute::StructRet)) {
if (FailureReason)
*FailureReason = "SRet arg to vararg function";
return false;
}
}
return true;
}
CallBase &llvm::promoteCall(CallBase &CB, Function *Callee,
CastInst **RetBitCast) {
assert(!CB.getCalledFunction() && "Only indirect call sites can be promoted");
// Set the called function of the call site to be the given callee (but don't
// change the type).
CB.setCalledOperand(Callee);
// Since the call site will no longer be direct, we must clear metadata that
// is only appropriate for indirect calls. This includes !prof and !callees
// metadata.
CB.setMetadata(LLVMContext::MD_prof, nullptr);
CB.setMetadata(LLVMContext::MD_callees, nullptr);
// If the function type of the call site matches that of the callee, no
// additional work is required.
if (CB.getFunctionType() == Callee->getFunctionType())
return CB;
// Save the return types of the call site and callee.
Type *CallSiteRetTy = CB.getType();
Type *CalleeRetTy = Callee->getReturnType();
// Change the function type of the call site the match that of the callee.
CB.mutateFunctionType(Callee->getFunctionType());
// Inspect the arguments of the call site. If an argument's type doesn't
// match the corresponding formal argument's type in the callee, bitcast it
// to the correct type.
auto CalleeType = Callee->getFunctionType();
auto CalleeParamNum = CalleeType->getNumParams();
LLVMContext &Ctx = Callee->getContext();
const AttributeList &CallerPAL = CB.getAttributes();
// The new list of argument attributes.
SmallVector<AttributeSet, 4> NewArgAttrs;
bool AttributeChanged = false;
for (unsigned ArgNo = 0; ArgNo < CalleeParamNum; ++ArgNo) {
auto *Arg = CB.getArgOperand(ArgNo);
Type *FormalTy = CalleeType->getParamType(ArgNo);
Type *ActualTy = Arg->getType();
if (FormalTy != ActualTy) {
auto *Cast =
CastInst::CreateBitOrPointerCast(Arg, FormalTy, "", CB.getIterator());
CB.setArgOperand(ArgNo, Cast);
// Remove any incompatible attributes for the argument.
AttrBuilder ArgAttrs(Ctx, CallerPAL.getParamAttrs(ArgNo));
ArgAttrs.remove(AttributeFuncs::typeIncompatible(FormalTy));
// We may have a different byval/inalloca type.
if (ArgAttrs.getByValType())
ArgAttrs.addByValAttr(Callee->getParamByValType(ArgNo));
if (ArgAttrs.getInAllocaType())
ArgAttrs.addInAllocaAttr(Callee->getParamInAllocaType(ArgNo));
NewArgAttrs.push_back(AttributeSet::get(Ctx, ArgAttrs));
AttributeChanged = true;
} else
NewArgAttrs.push_back(CallerPAL.getParamAttrs(ArgNo));
}
// If the return type of the call site doesn't match that of the callee, cast
// the returned value to the appropriate type.
// Remove any incompatible return value attribute.
AttrBuilder RAttrs(Ctx, CallerPAL.getRetAttrs());
if (!CallSiteRetTy->isVoidTy() && CallSiteRetTy != CalleeRetTy) {
createRetBitCast(CB, CallSiteRetTy, RetBitCast);
RAttrs.remove(AttributeFuncs::typeIncompatible(CalleeRetTy));
AttributeChanged = true;
}
// Set the new callsite attribute.
if (AttributeChanged)
CB.setAttributes(AttributeList::get(Ctx, CallerPAL.getFnAttrs(),
AttributeSet::get(Ctx, RAttrs),
NewArgAttrs));
return CB;
}
CallBase &llvm::promoteCallWithIfThenElse(CallBase &CB, Function *Callee,
MDNode *BranchWeights) {
// Version the indirect call site. If the called value is equal to the given
// callee, 'NewInst' will be executed, otherwise the original call site will
// be executed.
CallBase &NewInst = versionCallSite(CB, Callee, BranchWeights);
// Promote 'NewInst' so that it directly calls the desired function.
return promoteCall(NewInst, Callee);
}
CallBase &llvm::promoteCallWithVTableCmp(CallBase &CB, Instruction *VPtr,
Function *Callee,
ArrayRef<Constant *> AddressPoints,
MDNode *BranchWeights) {
assert(!AddressPoints.empty() && "Caller should guarantee");
IRBuilder<> Builder(&CB);
SmallVector<Value *, 2> ICmps;
for (auto &AddressPoint : AddressPoints)
ICmps.push_back(Builder.CreateICmpEQ(VPtr, AddressPoint));
// TODO: Perform tree height reduction if the number of ICmps is high.
Value *Cond = Builder.CreateOr(ICmps);
// Version the indirect call site. If Cond is true, 'NewInst' will be
// executed, otherwise the original call site will be executed.
CallBase &NewInst = versionCallSiteWithCond(CB, Cond, BranchWeights);
// Promote 'NewInst' so that it directly calls the desired function.
return promoteCall(NewInst, Callee);
}
bool llvm::tryPromoteCall(CallBase &CB) {
assert(!CB.getCalledFunction());
Module *M = CB.getCaller()->getParent();
const DataLayout &DL = M->getDataLayout();
Value *Callee = CB.getCalledOperand();
LoadInst *VTableEntryLoad = dyn_cast<LoadInst>(Callee);
if (!VTableEntryLoad)
return false; // Not a vtable entry load.
Value *VTableEntryPtr = VTableEntryLoad->getPointerOperand();
APInt VTableOffset(DL.getTypeSizeInBits(VTableEntryPtr->getType()), 0);
Value *VTableBasePtr = VTableEntryPtr->stripAndAccumulateConstantOffsets(
DL, VTableOffset, /* AllowNonInbounds */ true);
LoadInst *VTablePtrLoad = dyn_cast<LoadInst>(VTableBasePtr);
if (!VTablePtrLoad)
return false; // Not a vtable load.
Value *Object = VTablePtrLoad->getPointerOperand();
APInt ObjectOffset(DL.getTypeSizeInBits(Object->getType()), 0);
Value *ObjectBase = Object->stripAndAccumulateConstantOffsets(
DL, ObjectOffset, /* AllowNonInbounds */ true);
if (!(isa<AllocaInst>(ObjectBase) && ObjectOffset == 0))
// Not an Alloca or the offset isn't zero.
return false;
// Look for the vtable pointer store into the object by the ctor.
BasicBlock::iterator BBI(VTablePtrLoad);
Value *VTablePtr = FindAvailableLoadedValue(
VTablePtrLoad, VTablePtrLoad->getParent(), BBI, 0, nullptr, nullptr);
if (!VTablePtr)
return false; // No vtable found.
APInt VTableOffsetGVBase(DL.getTypeSizeInBits(VTablePtr->getType()), 0);
Value *VTableGVBase = VTablePtr->stripAndAccumulateConstantOffsets(
DL, VTableOffsetGVBase, /* AllowNonInbounds */ true);
GlobalVariable *GV = dyn_cast<GlobalVariable>(VTableGVBase);
if (!(GV && GV->isConstant() && GV->hasDefinitiveInitializer()))
// Not in the form of a global constant variable with an initializer.
return false;
APInt VTableGVOffset = VTableOffsetGVBase + VTableOffset;
if (!(VTableGVOffset.getActiveBits() <= 64))
return false; // Out of range.
Function *DirectCallee = nullptr;
std::tie(DirectCallee, std::ignore) =
getFunctionAtVTableOffset(GV, VTableGVOffset.getZExtValue(), *M);
if (!DirectCallee)
return false; // No function pointer found.
if (!isLegalToPromote(CB, DirectCallee))
return false;
// Success.
promoteCall(CB, DirectCallee);
return true;
}
#undef DEBUG_TYPE