[wasm-simd][arm64] Use unique register for shifts

The src register needs to be different from the temporary Simd128
register since in the codegen we modify tmp before using tmp and src.

Bug: chromium:1063006
Change-Id: I8b4b2d23d8f090ea37041e82cac97470bcf0d833
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2111110Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66799}

src/compiler/backend/arm64/instruction-selector-arm64.cc

@@ -164,8 +164,11 @@ void VisitSimdShiftRRR(InstructionSelector* selector, ArchOpcode opcode,
     }
   } else {
     InstructionOperand temps[] = {g.TempSimd128Register(), g.TempRegister()};
+    // We only need a unique register for the first input (src), since in
+    // the codegen we use tmp to store the shifts, and then later use it with
+    // src. The second input can be the same as the second temp (shift).
     selector->Emit(opcode, g.DefineAsRegister(node),
-                   g.UseRegister(node->InputAt(0)),
+                   g.UseUniqueRegister(node->InputAt(0)),
                    g.UseRegister(node->InputAt(1)), arraysize(temps), temps);
   }
 }