diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 8 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/sink-alloca.ll | 52 |
2 files changed, 57 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp index be7d43bbcf2..f530ee1246e 100644 --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -3065,9 +3065,11 @@ static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) { I->isTerminator()) return false; - // Do not sink alloca instructions out of the entry block. - if (isa<AllocaInst>(I) && I->getParent() == - &DestBlock->getParent()->getEntryBlock()) + // Do not sink static or dynamic alloca instructions. Static allocas must + // remain in the entry block, and dynamic allocas must not be sunk in between + // a stacksave / stackrestore pair, which would incorrectly shorten its + // lifetime. + if (isa<AllocaInst>(I)) return false; // Do not sink into catchswitch blocks. diff --git a/llvm/test/Transforms/InstCombine/sink-alloca.ll b/llvm/test/Transforms/InstCombine/sink-alloca.ll new file mode 100644 index 00000000000..f2de74ff533 --- /dev/null +++ b/llvm/test/Transforms/InstCombine/sink-alloca.ll @@ -0,0 +1,52 @@ +; RUN: opt -instcombine -S < %s | FileCheck %s + +target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128" +target triple = "i686-unknown-linux-gnu" + +; Check that instcombine doesn't sink dynamic allocas across llvm.stacksave. + +; Helper to generate branch conditions. +declare i1 @cond() + +declare i32* @use_and_return(i32*) + +declare i8* @llvm.stacksave() #0 + +declare void @llvm.stackrestore(i8*) #0 + +define void @foo(i32 %x) { +entry: + %c1 = call i1 @cond() + br i1 %c1, label %ret, label %nonentry + +nonentry: ; preds = %entry + %argmem = alloca i32, i32 %x, align 4 + %sp = call i8* @llvm.stacksave() + %c2 = call i1 @cond() + br i1 %c2, label %ret, label %sinktarget + +sinktarget: ; preds = %nonentry + ; Arrange for there to be a single use of %argmem by returning it. + %p = call i32* @use_and_return(i32* nonnull %argmem) + store i32 13, i32* %p, align 4 + call void @llvm.stackrestore(i8* %sp) + %0 = call i32* @use_and_return(i32* %p) + br label %ret + +ret: ; preds = %sinktarget, %nonentry, %entry + ret void +} + +; CHECK-LABEL: define void @foo(i32 %x) +; CHECK: nonentry: +; CHECK: %argmem = alloca i32, i32 %x +; CHECK: %sp = call i8* @llvm.stacksave() +; CHECK: %c2 = call i1 @cond() +; CHECK: br i1 %c2, label %ret, label %sinktarget +; CHECK: sinktarget: +; CHECK: %p = call i32* @use_and_return(i32* nonnull %argmem) +; CHECK: store i32 13, i32* %p +; CHECK: call void @llvm.stackrestore(i8* %sp) +; CHECK: %0 = call i32* @use_and_return(i32* %p) + +attributes #0 = { nounwind } |
