From cc10244d7725f191bdc91cd62befff0c97257c7b Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 6 Dec 2010 01:48:06 +0000 Subject: Fix PR8728, a miscompilation I recently introduced. When optimizing memcpy's like: memcpy(A, B) memcpy(A, C) we cannot delete the first memcpy as dead if A and C might be aliases. If so, we actually get: memcpy(A, B) memcpy(A, A) which is not correct to transform into: memcpy(A, A) This patch was heavily influenced by Jakub Staszak's patch in PR8728, thanks Jakub! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120974 91177308-0d34-0410-b5e6-96231b3b80d8 --- test/Transforms/DeadStoreElimination/simple.ll | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) (limited to 'test/Transforms/DeadStoreElimination') diff --git a/test/Transforms/DeadStoreElimination/simple.ll b/test/Transforms/DeadStoreElimination/simple.ll index 203cf37193..a61eac9729 100644 --- a/test/Transforms/DeadStoreElimination/simple.ll +++ b/test/Transforms/DeadStoreElimination/simple.ll @@ -203,7 +203,7 @@ define void @test16(i8* %P, i8* %Q) nounwind ssp { } ;; Overwrite of memset by memcpy. -define void @test17(i8* %P, i8* %Q) nounwind ssp { +define void @test17(i8* %P, i8* noalias %Q) nounwind ssp { tail call void @llvm.memset.i64(i8* %P, i8 42, i64 8, i32 1) tail call void @llvm.memcpy.i64(i8* %P, i8* %Q, i64 12, i32 1) ret void @@ -222,3 +222,17 @@ define void @test17v(i8* %P, i8* %Q) nounwind ssp { ; CHECK-NEXT: call void @llvm.memcpy ; CHECK-NEXT: ret } + +; PR8728 +; Do not delete instruction where possible situation is: +; A = B +; A = A +define void @test18(i8* %P, i8* %Q, i8* %R) nounwind ssp { + tail call void @llvm.memcpy.i64(i8* %P, i8* %Q, i64 12, i32 1) + tail call void @llvm.memcpy.i64(i8* %P, i8* %R, i64 12, i32 1) + ret void +; CHECK: @test18 +; CHECK-NEXT: call void @llvm.memcpy +; CHECK-NEXT: call void @llvm.memcpy +; CHECK-NEXT: ret +} -- cgit v1.2.3