From 85937de26b7553768abe958ee51b1cc19417b950 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Tue, 24 Feb 2009 02:17:42 +0000 Subject: [PATCH] Add a testcase for the problem fixed in r65289. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65365 91177308-0d34-0410-b5e6-96231b3b80d8 --- .../Transforms/InstCombine/stack-overalign.ll | 29 +++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 test/Transforms/InstCombine/stack-overalign.ll diff --git a/test/Transforms/InstCombine/stack-overalign.ll b/test/Transforms/InstCombine/stack-overalign.ll new file mode 100644 index 00000000000..45bdc2e0cbe --- /dev/null +++ b/test/Transforms/InstCombine/stack-overalign.ll @@ -0,0 +1,29 @@ +; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {align 32} | count 1 + +; It's tempting to have an instcombine in which the src pointer of a +; memcpy is aligned up to the alignment of the destination, however +; there are pitfalls. If the src is an alloca, aligning it beyond what +; the target's stack pointer is aligned at will require dynamic +; stack realignment, which can require functions that don't otherwise +; need a frame pointer to need one. +; +; Abstaining from this transform is not the only way to approach this +; issue. Some late phase could be smart enough to reduce alloca +; alignments when they are greater than they need to be. Or, codegen +; could do dynamic alignment for just the one alloca, and leave the +; main stack pointer at its standard alignment. + +@dst = global [1024 x i8] zeroinitializer, align 32 + +define void @foo() nounwind { +entry: + %src = alloca [1024 x i8], align 1 + %src1 = getelementptr [1024 x i8]* %src, i32 0, i32 0 + call void @llvm.memcpy.i32(i8* getelementptr ([1024 x i8]* @dst, i32 0, i32 0), i8* %src1, i32 1024, i32 1) + call void @frob(i8* %src1) nounwind + ret void +} + +declare void @llvm.memcpy.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind + +declare void @frob(i8*)