[wasm] Force (concat) shuffle to use register operands

Bug: v8:9608
Change-Id: I676fd49c35dd65d96f524a9b6e09722ff12d472e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1744910
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Auto-Submit: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63133}

src/compiler/backend/x64/instruction-selector-x64.cc

@@ -3123,6 +3123,8 @@ void InstructionSelector::VisitS8x16Shuffle(Node* node) {
     SwapShuffleInputs(node);
     is_swizzle = false;        // It's simpler to just handle the general case.
     no_same_as_first = false;  // SSE requires same-as-first.
+    // TODO(v8:9608): also see v8:9083
+    src1_needs_reg = true;
     opcode = kX64S8x16Alignr;
     // palignr takes a single imm8 offset.
     imms[imm_count++] = offset;