PPC: Optimize clearing higher bits of mulhw/mulhwu

Change-Id: Ie3e14a6ef4531349e81a8ae741bc7470c7e547ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2349468
Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#69343}

Author: Milad Farazmand

src/compiler/backend/ppc/code-generator-ppc.cc

@@ -1515,18 +1515,14 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       }
       break;
     case kPPC_MulHigh32:
-      __ mulhw(ip, i.InputRegister(0), i.InputRegister(1), i.OutputRCBit());
+      __ mulhw(r0, i.InputRegister(0), i.InputRegister(1), i.OutputRCBit());
       // High 32 bits are undefined and need to be cleared.
-      __ li(r0, Operand(-1));
-      __ clrldi(r0, r0, Operand(32));
-      __ and_(i.OutputRegister(), ip, r0);
+      __ clrldi(i.OutputRegister(), r0, Operand(32));
       break;
     case kPPC_MulHighU32:
-      __ mulhwu(ip, i.InputRegister(0), i.InputRegister(1), i.OutputRCBit());
+      __ mulhwu(r0, i.InputRegister(0), i.InputRegister(1), i.OutputRCBit());
       // High 32 bits are undefined and need to be cleared.
-      __ li(r0, Operand(-1));
-      __ clrldi(r0, r0, Operand(32));
-      __ and_(i.OutputRegister(), ip, r0);
+      __ clrldi(i.OutputRegister(), r0, Operand(32));
       break;
     case kPPC_MulDouble:
       ASSEMBLE_FLOAT_BINOP_RC(fmul, MiscField::decode(instr->opcode()));