[llvm] r223074 - [AArch64] Fix v2i8->i16 bitcast legalization.

[Ahmed Bougacha]

Author: ab
Date: Mon Dec  1 14:52:32 2014
New Revision: 223074

URL: http://llvm.org/viewvc/llvm-project?rev=223074&view=rev
Log:
[AArch64] Fix v2i8->i16 bitcast legalization.

r213378 improved f16 bitcasts, so that they go directly through subregs,
instead of through the stack.  That code now causes an assertion failure
for bitcasts from other 16-bits types (most importantly v2i8).

Correct that by doing the custom lowering for i16 bitcasts only when the
input is an f16.

Part of PR21549.

Differential Revision: http://reviews.llvm.org/D6307

Added:
    llvm/trunk/test/CodeGen/AArch64/bitcast-v2i8.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=223074&r1=223073&r2=223074&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ISelLowering.cpp Mon Dec  1 14:52:32 2014
@@ -8697,13 +8697,12 @@ bool AArch64TargetLowering::getPostIndex
 
 static void ReplaceBITCASTResults(SDNode *N, SmallVectorImpl<SDValue> &Results,
                                   SelectionDAG &DAG) {
-  if (N->getValueType(0) != MVT::i16)
-    return;
-
   SDLoc DL(N);
   SDValue Op = N->getOperand(0);
-  assert(Op.getValueType() == MVT::f16 &&
-         "Inconsistent bitcast? Only 16-bit types should be i16 or f16");
+
+  if (N->getValueType(0) != MVT::i16 || Op.getValueType() != MVT::f16)
+    return;
+
   Op = SDValue(
       DAG.getMachineNode(TargetOpcode::INSERT_SUBREG, DL, MVT::f32,
                          DAG.getUNDEF(MVT::i32), Op,

Added: llvm/trunk/test/CodeGen/AArch64/bitcast-v2i8.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/bitcast-v2i8.ll?rev=223074&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/bitcast-v2i8.ll (added)
+++ llvm/trunk/test/CodeGen/AArch64/bitcast-v2i8.ll Mon Dec  1 14:52:32 2014
@@ -0,0 +1,15 @@
+; RUN: llc < %s -mtriple=aarch64-apple-ios | FileCheck %s
+
+; Part of PR21549: going through the stack isn't ideal but is correct.
+
+define i16 @test_bitcast_v2i8_to_i16(<2 x i8> %a) {
+; CHECK-LABEL: test_bitcast_v2i8_to_i16
+; CHECK:      mov.s   [[WREG_HI:w[0-9]+]], v0[1]
+; CHECK-NEXT: fmov    [[WREG_LO:w[0-9]+]], s0
+; CHECK-NEXT: strb    [[WREG_HI]], [sp, #15]
+; CHECK-NEXT: strb    [[WREG_LO]], [sp, #14]
+; CHECK-NEXT: ldrh    w0, [sp, #14]
+
+  %aa = bitcast <2 x i8> %a to i16
+  ret i16 %aa
+}