[AMDGPU] Enable code selection using `s_mul_hi_u32`/`s_mul_hi_i32`.

Subscribers: arsenm, kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59501

llvm-svn: 356405
diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index abd324e..878b456 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -3210,6 +3210,8 @@
     return AMDGPU::V_SUB_I32_e32;
   case AMDGPU::S_SUBB_U32: return AMDGPU::V_SUBB_U32_e32;
   case AMDGPU::S_MUL_I32: return AMDGPU::V_MUL_LO_I32;
+  case AMDGPU::S_MUL_HI_U32: return AMDGPU::V_MUL_HI_U32;
+  case AMDGPU::S_MUL_HI_I32: return AMDGPU::V_MUL_HI_I32;
   case AMDGPU::S_AND_B32: return AMDGPU::V_AND_B32_e64;
   case AMDGPU::S_OR_B32: return AMDGPU::V_OR_B32_e64;
   case AMDGPU::S_XOR_B32: return AMDGPU::V_XOR_B32_e64;
@@ -3254,6 +3256,8 @@
   case AMDGPU::S_CBRANCH_SCC0: return AMDGPU::S_CBRANCH_VCCZ;
   case AMDGPU::S_CBRANCH_SCC1: return AMDGPU::S_CBRANCH_VCCNZ;
   }
+  llvm_unreachable(
+      "Unexpected scalar opcode without corresponding vector one!");
 }
 
 const TargetRegisterClass *SIInstrInfo::getOpRegClass(const MachineInstr &MI,
diff --git a/llvm/lib/Target/AMDGPU/SOPInstructions.td b/llvm/lib/Target/AMDGPU/SOPInstructions.td
index d1b1352..73b66d82 100644
--- a/llvm/lib/Target/AMDGPU/SOPInstructions.td
+++ b/llvm/lib/Target/AMDGPU/SOPInstructions.td
@@ -548,8 +548,12 @@
     def S_LSHL4_ADD_U32 : SOP2_32<"s_lshl4_add_u32">;
   } // End Defs = [SCC]
 
-  def S_MUL_HI_U32 : SOP2_32<"s_mul_hi_u32">;
-  def S_MUL_HI_I32 : SOP2_32<"s_mul_hi_i32">;
+  let isCommutable = 1 in {
+    def S_MUL_HI_U32 : SOP2_32<"s_mul_hi_u32",
+      [(set i32:$sdst, (UniformBinFrag<mulhu> SSrc_b32:$src0, SSrc_b32:$src1))]>;
+    def S_MUL_HI_I32 : SOP2_32<"s_mul_hi_i32",
+      [(set i32:$sdst, (UniformBinFrag<mulhs> SSrc_b32:$src0, SSrc_b32:$src1))]>;
+  }
 }
 
 //===----------------------------------------------------------------------===//