X86: Disable generation of rep;movsl when %esi is used as a base pointer.
This happens when there is both stack realignment and a dynamic alloca in the
function. If we overwrite %esi (rep;movsl uses fixed registers) we'll lose the
base pointer and the next register spill will write into oblivion.
Fixes PR15249 and unbreaks firefox on i386/freebsd. Mozilla uses dynamic allocas
and freebsd a 4 byte stack alignment.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175057 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/X86/stack-align-memcpy.ll b/test/CodeGen/X86/stack-align-memcpy.ll
new file mode 100644
index 0000000..74945e5
--- /dev/null
+++ b/test/CodeGen/X86/stack-align-memcpy.ll
@@ -0,0 +1,18 @@
+; RUN: llc < %s -force-align-stack -mtriple i386-apple-darwin -mcpu=i486 | FileCheck %s
+
+%struct.foo = type { [88 x i8] }
+
+; PR15249
+; We can't use rep;movsl here because it clobbers the base pointer in %esi.
+define void @test1(%struct.foo* nocapture %x, i32 %y) nounwind {
+ %dynalloc = alloca i8, i32 %y, align 1
+ call void @bar(i8* %dynalloc, %struct.foo* align 4 byval %x)
+ ret void
+
+; CHECK: test1:
+; CHECK: andl $-16, %esp
+; CHECK: movl %esp, %esi
+; CHECK-NOT: rep;movsl
+}
+
+declare void @bar(i8* nocapture, %struct.foo* align 4 byval) nounwind