[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223074 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AArch64/AArch64ISelLowering.cpp b/lib/Target/AArch64/AArch64ISelLowering.cpp
index 6da468ed6b14d650bb6e3d88eafeaa889dfbed2a..16ad2f6e3b541e120269a6cdb8bdfef298adb6e6 100644 (file)
--- a/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -8697,13 +8697,12 @@ bool AArch64TargetLowering::getPostIndexedAddressParts(
 
 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,

diff --git a/test/CodeGen/AArch64/bitcast-v2i8.ll b/test/CodeGen/AArch64/bitcast-v2i8.ll
new file mode 100644 (file)
index 0000000..4bdac64
--- /dev/null
+++ b/test/CodeGen/AArch64/bitcast-v2i8.ll
@@ -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
+}