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Revert "[DSE] Enable removal of lifetime intrinsics in terminating blocks" 

llvm-svn: 245543
This commit is contained in:
Bjorn Steinbrink 2015-08-20 08:58:47 +00:00
parent cc7e8a9705
commit 2e2f66557e
2 changed files with 5 additions and 81 deletions
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33
llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -788,33 +788,15 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
const DataLayout &DL = BB.getModule()->getDataLayout();
// becomes false once lifetime intrinsics are observable or useful for stack
// coloring
bool canRemoveLifetimeIntrinsics = true;
// Scan the basic block backwards
for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ){
--BBI;
Value *V = nullptr;
if (canRemoveLifetimeIntrinsics)
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
V = II->getArgOperand(1);
break;
}
if (!V && hasMemoryWrite(BBI, *TLI) && isRemovable(BBI))
V = getStoredPointerOperand(BBI);
// If we found a store, check to see if it points into a dead stack value.
if (V) {
// If we find a store, check to see if it points into a dead stack value.
if (hasMemoryWrite(BBI, *TLI) && isRemovable(BBI)) {
// See through pointer-to-pointer bitcasts
SmallVector<Value *, 4> Pointers;
GetUnderlyingObjects(V, Pointers, DL);
GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers, DL);
// Stores to stack values are valid candidates for removal.
bool AllDead = true;
@ -862,15 +844,6 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
continue;
}
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
// We found a lifetime start for a live object, which we could not
// remove. So we must stop removing lifetime intrinsics from this block
// because they're useful for stack coloring again
canRemoveLifetimeIntrinsics = false;
continue;
}
if (auto CS = CallSite(BBI)) {
// Remove allocation function calls from the list of dead stack objects;
// there can't be any references before the definition.

53
llvm/test/Transforms/DeadStoreElimination/lifetime.ll
View File

@ -5,16 +5,14 @@ target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:1
declare void @llvm.lifetime.start(i64, i8* nocapture) nounwind
declare void @llvm.lifetime.end(i64, i8* nocapture) nounwind
declare void @llvm.memset.p0i8.i8(i8* nocapture, i8, i8, i32, i1) nounwind
declare void @callee(i8*)
define void @test1() {
; CHECK-LABEL: @test1(
%A = alloca i8
store i8 0, i8* %A ;; Written to by memset
; CHECK-NOT: store
call void @llvm.lifetime.end(i64 1, i8* %A)
; CHECK-NOT: lifetime.end
; CHECK: lifetime.end
call void @llvm.memset.p0i8.i8(i8* %A, i8 0, i8 -1, i32 0, i1 false)
; CHECK-NOT: memset
@ -24,7 +22,7 @@ define void @test1() {
}
define void @test2(i32* %P) {
; CHECK-LABEL: test2
; CHECK: test2
%Q = getelementptr i32, i32* %P, i32 1
%R = bitcast i32* %Q to i8*
call void @llvm.lifetime.start(i64 4, i8* %R)
@ -36,51 +34,4 @@ define void @test2(i32* %P) {
ret void
}
define void @test3(i8*) {
; CHECK-LABEL: test3
%a = alloca i8
call void @llvm.lifetime.start(i64 1, i8* %a)
; CHECK-NOT: lifetime.start
call void @llvm.lifetime.end(i64 1, i8* %a)
; CHECK-NOT: lifetime.end
call void @llvm.lifetime.start(i64 1, i8* undef)
; CHECK-NOT: lifetime.start
call void @llvm.lifetime.end(i64 1, i8* undef)
; CHECK-NOT: lifetime.end
ret void
}
define void @test4(i8*) {
; CHECK-LABEL: test4
%a = alloca i8
call void @llvm.lifetime.start(i64 1, i8* %a)
; CHECK: lifetime.start
call void @llvm.lifetime.end(i64 1, i8* %a)
; CHECK: lifetime.end
call void @llvm.lifetime.start(i64 1, i8* %0)
; CHECK: lifetime.start
call void @llvm.lifetime.end(i64 1, i8* %0)
; CHECK: lifetime.end
call void @llvm.lifetime.start(i64 1, i8* %a)
; CHECK-NOT: lifetime.start
call void @llvm.lifetime.end(i64 1, i8* %a)
; CHECK-NOT: lifetime.end
ret void
}
define void @test5() {
; CHECK-LABEL: test5
%a = alloca i8
%b = alloca i8
call void @llvm.lifetime.start(i64 1, i8* %a)
; CHECK: lifetime.start
call void @llvm.lifetime.end(i64 1, i8* %a)
; CHECK: lifetime.end
call void @llvm.lifetime.start(i64 1, i8* %b)
; CHECK: lifetime.start
call void @callee(i8* %b)
; CHECK: call void @callee
call void @llvm.lifetime.end(i64 1, i8* %b)
; CHECK-NOT: lifetime.end
ret void
}