AMDGPU/GlobalISel: Mark G_BITCAST s32 <--> <2 x s16> legal

Reviewers: arsenm

Reviewed By: arsenm

Subscribers: kzhuravl, wdng, nhaehnle, yaxunl, rovka, kristof.beyls, igorb, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D34129

llvm-svn: 305692

lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp

@@ -29,6 +29,7 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo() {
   using namespace TargetOpcode;
 
   const LLT S1= LLT::scalar(1);
+  const LLT V2S16 = LLT::vector(2, 16);
   const LLT S32 = LLT::scalar(32);
   const LLT S64 = LLT::scalar(64);
   const LLT P1 = LLT::pointer(1, 64);
@@ -36,6 +37,12 @@ AMDGPULegalizerInfo::AMDGPULegalizerInfo() {
 
   setAction({G_ADD, S32}, Legal);
 
+  setAction({G_BITCAST, V2S16}, Legal);
+  setAction({G_BITCAST, 1, S32}, Legal);
+
+  setAction({G_BITCAST, S32}, Legal);
+  setAction({G_BITCAST, 1, V2S16}, Legal);
+
   // FIXME: i1 operands to intrinsics should always be legal, but other i1
   // values may not be legal.  We need to figure out how to distinguish
   // between these two scenarios.

test/CodeGen/AMDGPU/GlobalISel/legalize-bitcast.mir

@@ -0,0 +1,23 @@
+# RUN: llc -mtriple=amdgcn-mesa-mesa3d -mcpu=fiji -run-pass=legalizer -global-isel %s -o - | FileCheck %s
+
+--- |
+  define void @test_bitcast() { ret void }
+...
+
+---
+name:            test_bitcast
+registers:
+  - { id: 0, class: _ }
+  - { id: 1, class: _ }
+  - { id: 2, class: _ }
+body: |
+  bb.0:
+    liveins: %vgpr0
+    ; CHECK-LABEL: name: test_bitcast
+    ; CHECK: %1(<2 x s16>) = G_BITCAST %0
+    ; CHECK: %2(s32) = G_BITCAST %1
+
+    %0(s32) = COPY %vgpr0
+    %1(<2 x s16>) = G_BITCAST %0
+    %2(s32) = G_BITCAST %1
+...