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;
- // If we find a store, check to see if it points into a dead stack value.
- if (hasMemoryWrite(BBI, *TLI) && isRemovable(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) {
// See through pointer-to-pointer bitcasts
SmallVector<Value *, 4> Pointers;
- GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers, DL);
+ GetUnderlyingObjects(V, Pointers, DL);
// Stores to stack values are valid candidates for removal.
bool AllDead = true;
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.
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: lifetime.end
+; CHECK-NOT: lifetime.end
call void @llvm.memset.p0i8.i8(i8* %A, i8 0, i8 -1, i32 0, i1 false)
; CHECK-NOT: memset
}
define void @test2(i32* %P) {
-; CHECK: test2
+; CHECK-LABEL: test2
%Q = getelementptr i32, i32* %P, i32 1
%R = bitcast i32* %Q to i8*
call void @llvm.lifetime.start(i64 4, i8* %R)
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
+}