[wasm-relaxed-simd][ia32] Prototype i8x16 relaxed swizzle

ia32 port of 9ffb4829

Bug: v8:12284
Change-Id: Id396ee6d169c893804297934df63120704cef745
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3255663Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77809}

src/compiler/backend/ia32/instruction-selector-ia32.cc

@@ -3014,13 +3014,18 @@ void InstructionSelector::VisitI8x16Shuffle(Node* node) {
 void InstructionSelector::VisitI8x16Swizzle(Node* node) {
   InstructionCode op = kIA32I8x16Swizzle;
 
-  auto m = V128ConstMatcher(node->InputAt(1));
-  if (m.HasResolvedValue()) {
-    // If the indices vector is a const, check if they are in range, or if the
-    // top bit is set, then we can avoid the paddusb in the codegen and simply
-    // emit a pshufb.
-    auto imms = m.ResolvedValue().immediate();
-    op |= MiscField::encode(wasm::SimdSwizzle::AllInRangeOrTopBitSet(imms));
+  bool relaxed = OpParameter<bool>(node->op());
+  if (relaxed) {
+    op |= MiscField::encode(true);
+  } else {
+    auto m = V128ConstMatcher(node->InputAt(1));
+    if (m.HasResolvedValue()) {
+      // If the indices vector is a const, check if they are in range, or if the
+      // top bit is set, then we can avoid the paddusb in the codegen and simply
+      // emit a pshufb.
+      auto imms = m.ResolvedValue().immediate();
+      op |= MiscField::encode(wasm::SimdSwizzle::AllInRangeOrTopBitSet(imms));
+    }
   }
 
   IA32OperandGenerator g(this);

test/cctest/wasm/test-run-wasm-relaxed-simd.cc

@@ -385,9 +385,7 @@ WASM_RELAXED_SIMD_TEST(I32x4RelaxedTruncF32x4U) {
   IntRelaxedTruncFloatTest<uint32_t, float>(
       execution_tier, kExprI32x4RelaxedTruncF32x4U, kExprF32x4Splat);
 }
-#endif  // V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32
 
-#if V8_TARGET_ARCH_X64
 WASM_RELAXED_SIMD_TEST(I8x16RelaxedSwizzle) {
   // Output is only defined for indices in the range [0,15].
   WasmRunner<int32_t> r(execution_tier);
@@ -409,7 +407,7 @@ WASM_RELAXED_SIMD_TEST(I8x16RelaxedSwizzle) {
     CHECK_EQ(LANE(dst, i), i);
   }
 }
-#endif  // V8_TARGET_ARCH_X64
+#endif  // V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32
 
 #undef WASM_RELAXED_SIMD_TEST
 }  // namespace test_run_wasm_relaxed_simd