Fix the root cause of PR15348 by correctly handling alignment 0 on

memory intrinsics in the SDAG builder.

When alignment is zero, the lang ref says that *no* alignment
assumptions can be made. This is the exact opposite of the internal API
contracts of the DAG where alignment 0 indicates that the alignment can
be made to be anything desired.

There is another, more explicit alignment that is better suited for the
role of "no alignment at all": an alignment of 1. Map the intrinsic
alignment to this early so that we don't end up generating aligned DAGs.

It is really terrifying that we've never seen this before, but we
suddenly started generating a large number of alignment 0 memcpys due to
the new code to do memcpy-based copying of POD class members. That patch
contains a bug that rounds bitfield alignments down when they are the
first field. This can in turn produce zero alignments.

This fixes weird crashes I've seen in library users of LLVM on 32-bit
hosts, etc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176022 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 29 insertions, 0 deletions

diff --git a/test/CodeGen/X86/memcpy.ll b/test/CodeGen/X86/memcpy.ll
index 2e02e45..3372a4a 100644
--- a/test/CodeGen/X86/memcpy.ll
+++ b/test/CodeGen/X86/memcpy.ll
@@ -105,3 +105,16 @@ entry:
   ret void
 }
 
+define void @PR15348(i8* %a, i8* %b) {
+; Ensure that alignment of '0' in an @llvm.memcpy intrinsic results in
+; unaligned loads and stores.
+; LINUX: PR15348
+; LINUX: movb
+; LINUX: movb
+; LINUX: movq
+; LINUX: movq
+; LINUX: movq
+; LINUX: movq
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %a, i8* %b, i64 17, i32 0, i1 false)
+  ret void
+}
diff --git a/test/CodeGen/X86/memset.ll b/test/CodeGen/X86/memset.ll
index b35f261..0d479f0 100644
--- a/test/CodeGen/X86/memset.ll
+++ b/test/CodeGen/X86/memset.ll
@@ -20,15 +20,18 @@ entry:
 ; X86: movl $0,
 ; X86: movl $0,
 ; X86-NOT: movl $0,
+; X86: ret
 
 ; XMM: xorps %xmm{{[0-9]+}}, [[Z:%xmm[0-9]+]]
 ; XMM: movaps [[Z]],
 ; XMM: movaps [[Z]],
 ; XMM-NOT: movaps
+; XMM: ret
 
 ; YMM: vxorps %ymm{{[0-9]+}}, %ymm{{[0-9]+}}, [[Z:%ymm[0-9]+]]
 ; YMM: vmovaps [[Z]],
 ; YMM-NOT: movaps
+; YMM: ret
 
 	call void @foo( %struct.x* %up_mvd116 ) nounwind 
 	ret void
@@ -37,3 +40,16 @@ entry:
 declare void @foo(%struct.x*)
 
 declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
+
+define void @PR15348(i8* %a) {
+; Ensure that alignment of '0' in an @llvm.memset intrinsic results in
+; unaligned loads and stores.
+; XMM: PR15348
+; XMM: movb $0,
+; XMM: movl $0,
+; XMM: movl $0,
+; XMM: movl $0,
+; XMM: movl $0,
+  call void @llvm.memset.p0i8.i64(i8* %a, i8 0, i64 17, i32 0, i1 false)
+  ret void
+}