[wasm-simd] Fix code generation for Integer Splats.

Integer splats should use an operand when a register is not allocated.

Bug: V8:8927
Change-Id: I14c80b7b073fae3754ec32f4fa8605af399ef341
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1513102Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60138}

src/compiler/backend/x64/code-generator-x64.cc

@@ -2344,7 +2344,11 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     }
     case kX64I32x4Splat: {
       XMMRegister dst = i.OutputSimd128Register();
-      __ movd(dst, i.InputRegister(0));
+      if (instr->InputAt(0)->IsRegister()) {
+        __ movd(dst, i.InputRegister(0));
+      } else {
+        __ movd(dst, i.InputOperand(0));
+      }
       __ pshufd(dst, dst, 0x0);
       break;
     }
@@ -2543,7 +2547,11 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     }
     case kX64I16x8Splat: {
       XMMRegister dst = i.OutputSimd128Register();
-      __ movd(dst, i.InputRegister(0));
+      if (instr->InputAt(0)->IsRegister()) {
+        __ movd(dst, i.InputRegister(0));
+      } else {
+        __ movd(dst, i.InputOperand(0));
+      }
       __ pshuflw(dst, dst, 0x0);
       __ pshufd(dst, dst, 0x0);
       break;
@@ -2728,7 +2736,11 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     case kX64I8x16Splat: {
       CpuFeatureScope sse_scope(tasm(), SSSE3);
       XMMRegister dst = i.OutputSimd128Register();
-      __ movd(dst, i.InputRegister(0));
+      if (instr->InputAt(0)->IsRegister()) {
+        __ movd(dst, i.InputRegister(0));
+      } else {
+        __ movd(dst, i.InputOperand(0));
+      }
       __ xorps(kScratchDoubleReg, kScratchDoubleReg);
       __ pshufb(dst, kScratchDoubleReg);
       break;