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Teach InstCombine that lifetime intrincs aren't a real user on the result of a

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malloc call.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136732 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-08-02 22:08:01 +00:00
parent 0e0a8806d4
commit d8030c79fd
2 changed files with 48 additions and 12 deletions
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46
lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -1043,7 +1043,10 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
static bool IsOnlyNullComparedAndFreed(const Value &V) {
static bool IsOnlyNullComparedAndFreed(const Value &V, int Depth = 0) {
if (Depth == 8)
return false;
for (Value::const_use_iterator UI = V.use_begin(), UE = V.use_end();
UI != UE; ++UI) {
const User *U = *UI;
@ -1052,6 +1055,20 @@ static bool IsOnlyNullComparedAndFreed(const Value &V) {
if (const ICmpInst *ICI = dyn_cast<ICmpInst>(U))
if (ICI->isEquality() && isa<ConstantPointerNull>(ICI->getOperand(1)))
continue;
if (const BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
if (IsOnlyNullComparedAndFreed(*BCI, Depth+1))
continue;
}
if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
if (GEPI->hasAllZeroIndices() &&
IsOnlyNullComparedAndFreed(*GEPI, Depth+1))
continue;
}
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end)
continue;
}
return false;
}
return true;
@ -1064,22 +1081,29 @@ Instruction *InstCombiner::visitMalloc(Instruction &MI) {
if (IsOnlyNullComparedAndFreed(MI)) {
for (Value::use_iterator UI = MI.use_begin(), UE = MI.use_end();
UI != UE;) {
// We can assume that every remaining use is a free call or an icmp eq/ne
// to null, so the cast is safe.
// All the users permitted by IsOnlyNullComparedAndFreed are Instructions.
Instruction *I = cast<Instruction>(*UI);
// Early increment here, as we're about to get rid of the user.
++UI;
if (isFreeCall(I)) {
EraseInstFromFunction(*cast<CallInst>(I));
continue;
if (CallInst *CI = isFreeCall(I)) {
if (CI != I)
EraseInstFromFunction(*CI);
EraseInstFromFunction(*I);
} else if (ICmpInst *C = dyn_cast<ICmpInst>(I)) {
ReplaceInstUsesWith(*C,
ConstantInt::get(Type::getInt1Ty(C->getContext()),
C->isFalseWhenEqual()));
EraseInstFromFunction(*C);
} else if (I->getType()->isVoidTy()) {
// An all-zero GEP or a bitcast.
ReplaceInstUsesWith(*I, UndefValue::get(I->getType()));
EraseInstFromFunction(*I);
} else {
// A lifetime intrinsic.
EraseInstFromFunction(*I);
}
// Again, the cast is safe.
ICmpInst *C = cast<ICmpInst>(I);
ReplaceInstUsesWith(*C, ConstantInt::get(Type::getInt1Ty(C->getContext()),
C->isFalseWhenEqual()));
EraseInstFromFunction(*C);
}
return EraseInstFromFunction(MI);
}

14
test/Transforms/InstCombine/malloc-free-delete.ll
View File

@ -12,7 +12,7 @@ define i32 @main(i32 %argc, i8** %argv) {
; CHECK: ret i32 0
}
declare i8* @malloc(i32)
declare noalias i8* @malloc(i32)
declare void @free(i8*)
define i1 @foo() {
@ -23,3 +23,15 @@ define i1 @foo() {
call void @free(i8* %m)
ret i1 %z
}
declare void @llvm.lifetime.start(i64, i8*)
declare void @llvm.lifetime.end(i64, i8*)
define void @test3() {
; CHECK: @test3
; CHECK-NEXT: ret void
%a = call noalias i8* @malloc(i32 10)
call void @llvm.lifetime.start(i64 10, i8* %a)
call void @llvm.lifetime.end(i64 10, i8* %a)
ret void
}