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Teach DSE to eliminate useless trampolines.

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llvm-svn: 86683
This commit is contained in:
Duncan Sands 2009-11-10 13:49:50 +00:00
parent a25c87ef1f
commit 732a2ed037
2 changed files with 35 additions and 6 deletions
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25
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -87,13 +87,13 @@ static bool doesClobberMemory(Instruction *I) {
switch (II->getIntrinsicID()) {
default: return false;
case Intrinsic::memset: case Intrinsic::memmove: case Intrinsic::memcpy:
case Intrinsic::lifetime_end: return true;
case Intrinsic::init_trampoline: case Intrinsic::lifetime_end: return true;
}
}
return false;
}
/// isElidable - If the memory this instruction and the memory it writes to is
/// isElidable - If the value of this instruction and the memory it writes to is
/// unused, may we delete this instrtction?
static bool isElidable(Instruction *I) {
assert(doesClobberMemory(I));
@ -111,8 +111,15 @@ static Value *getPointerOperand(Instruction *I) {
return SI->getPointerOperand();
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(I))
return MI->getOperand(1);
assert(cast<IntrinsicInst>(I)->getIntrinsicID() == Intrinsic::lifetime_end);
return cast<IntrinsicInst>(I)->getOperand(2);
IntrinsicInst *II = cast<IntrinsicInst>(I);
switch (II->getIntrinsicID()) {
default:
assert(false && "Unexpected intrinsic!");
case Intrinsic::init_trampoline:
return II->getOperand(1);
case Intrinsic::lifetime_end:
return II->getOperand(2);
}
}
/// getStoreSize - Return the length in bytes of the write by the clobbering
@ -129,8 +136,14 @@ static unsigned getStoreSize(Instruction *I, const TargetData *TD) {
Len = MI->getLength();
} else {
IntrinsicInst *II = cast<IntrinsicInst>(I);
assert(II->getIntrinsicID() == Intrinsic::lifetime_end);
Len = II->getOperand(0);
switch (II->getIntrinsicID()) {
default:
assert(false && "Unexpected intrinsic!");
case Intrinsic::init_trampoline:
return -1u;
case Intrinsic::lifetime_end:
Len = II->getOperand(0);
}
}
if (ConstantInt *LenCI = dyn_cast<ConstantInt>(Len))
if (!LenCI->isAllOnesValue())

16
test/Transforms/DeadStoreElimination/2009-11-10-Trampoline.ll Normal file
View File

@ -0,0 +1,16 @@
; RUN: opt -S -dse < %s | FileCheck %s
declare i8* @llvm.init.trampoline(i8*, i8*, i8*)
declare void @f()
define void @unused_trampoline() {
; CHECK: @unused_trampoline
%storage = alloca [10 x i8], align 16 ; <[10 x i8]*> [#uses=1]
; CHECK-NOT: alloca
%cast = getelementptr [10 x i8]* %storage, i32 0, i32 0 ; <i8*> [#uses=1]
%tramp = call i8* @llvm.init.trampoline( i8* %cast, i8* bitcast (void ()* @f to i8*), i8* null ) ; <i8*> [#uses=1]
; CHECK-NOT: trampoline
ret void
; CHECK: ret void
}