[llvm] r234462 - [AArch64] Teach AArch64TargetLowering::getOptimalMemOpType to consider alignment

[Lang Hames]

Author: lhames
Date: Wed Apr  8 22:40:33 2015
New Revision: 234462

URL: http://llvm.org/viewvc/llvm-project?rev=234462&view=rev
Log:
[AArch64] Teach AArch64TargetLowering::getOptimalMemOpType to consider alignment
restrictions when choosing a type for small-memcpy inlining in
SelectionDAGBuilder.

This ensures that the loads and stores output for the memcpy won't be further
expanded during legalization, which would cause the total number of instructions
for the memcpy to exceed (often significantly) the inlining thresholds.

<rdar://problem/17829180>


Added:
    llvm/trunk/test/CodeGen/AArch64/arm64-misaligned-memcpy-inline.ll
Modified:
    llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp

Modified: llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp?rev=234462&r1=234461&r2=234462&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp Wed Apr  8 22:40:33 2015
@@ -6664,7 +6664,17 @@ EVT AArch64TargetLowering::getOptimalMem
        (allowsMisalignedMemoryAccesses(MVT::f128, 0, 1, &Fast) && Fast)))
     return MVT::f128;
 
-  return Size >= 8 ? MVT::i64 : MVT::i32;
+  if (Size >= 8 &&
+      (memOpAlign(SrcAlign, DstAlign, 8) ||
+       (allowsMisalignedMemoryAccesses(MVT::i64, 0, 1, &Fast) && Fast)))
+    return MVT::i64;
+
+  if (Size >= 4 &&
+      (memOpAlign(SrcAlign, DstAlign, 4) ||
+       (allowsMisalignedMemoryAccesses(MVT::i32, 0, 1, &Fast) && Fast)))
+    return MVT::i64;
+
+  return MVT::Other;
 }
 
 // 12-bit optionally shifted immediates are legal for adds.

Added: llvm/trunk/test/CodeGen/AArch64/arm64-misaligned-memcpy-inline.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/arm64-misaligned-memcpy-inline.ll?rev=234462&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/arm64-misaligned-memcpy-inline.ll (added)
+++ llvm/trunk/test/CodeGen/AArch64/arm64-misaligned-memcpy-inline.ll Wed Apr  8 22:40:33 2015
@@ -0,0 +1,14 @@
+; RUN: llc -march=arm64 -aarch64-strict-align < %s | FileCheck %s
+
+; Small (16-bytes here) unaligned memcpys should stay memcpy calls if
+; strict-alignment is turned on.
+define void @t0(i8* %out, i8* %in) {
+; CHECK-LABEL: t0:
+; CHECK:         orr w2, wzr, #0x10
+; CHECK-NEXT:    bl _memcpy
+entry:
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %out, i8* %in, i64 16, i32 1, i1 false)
+  ret void
+}
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1)