s390: [wasm] Use a single register when visiting S128Zero

Change-Id: I7c4f06d53e7b58b902f929944c03dc7c65bf4abf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2115935Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#66832}

src/compiler/backend/s390/code-generator-s390.cc

@@ -3916,8 +3916,7 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     }
     case kS390_S128Zero: {
       Simd128Register dst = i.OutputSimd128Register();
-      Simd128Register src = i.InputSimd128Register(1);
-      __ vx(dst, dst, src, Condition(0), Condition(0), Condition(0));
+      __ vx(dst, dst, dst, Condition(0), Condition(0), Condition(0));
       break;
     }
     case kS390_S128Select: {

src/compiler/backend/s390/instruction-selector-s390.cc

@@ -2822,7 +2822,7 @@ void InstructionSelector::VisitS8x16Swizzle(Node* node) {
 
 void InstructionSelector::VisitS128Zero(Node* node) {
   S390OperandGenerator g(this);
-  Emit(kS390_S128Zero, g.DefineAsRegister(node), g.DefineAsRegister(node));
+  Emit(kS390_S128Zero, g.DefineAsRegister(node));
 }
 
 void InstructionSelector::VisitS128Select(Node* node) {