[wasm] SIMD/Atomics ops update to use the right prefix opcodes

src/wasm/function-body-decoder.cc

Index: src/wasm/function-body-decoder.cc
diff --git a/src/wasm/function-body-decoder.cc b/src/wasm/function-body-decoder.cc
index 7a2006f32baf30588a6a34b3a1e5d6a9b76c36d3..12fe67c2e674e1c8b6a6d75671691b2124a52941 100644
--- a/src/wasm/function-body-decoder.cc
+++ b/src/wasm/function-body-decoder.cc
@@ -495,14 +495,17 @@ class WasmDecoder : public Decoder {
 #define DECLARE_OPCODE_CASE(name, opcode, sig) case kExpr##name:
           FOREACH_SIMD_0_OPERAND_OPCODE(DECLARE_OPCODE_CASE)
 #undef DECLARE_OPCODE_CASE
-          {
-            return 2;
-          }
+          return 2;
 #define DECLARE_OPCODE_CASE(name, opcode, sig) case kExpr##name:
           FOREACH_SIMD_1_OPERAND_OPCODE(DECLARE_OPCODE_CASE)
+#undef DECLARE_OPCODE_CASE
+          return 3;
+#define DECLARE_OPCODE_CASE(name, opcode, sig) case kExpr##name:
+          FOREACH_SIMD_MEM_OPCODE(DECLARE_OPCODE_CASE)
 #undef DECLARE_OPCODE_CASE
           {
-            return 3;
+            MemoryAccessOperand<true> operand(decoder, pc + 1, UINT32_MAX);
+            return 2 + operand.length;
           }
           // Shuffles require a byte per lane, or 16 immediate bytes.
           case kExprS8x16Shuffle:
@@ -523,14 +526,19 @@ class WasmDecoder : public Decoder {
     FunctionSig* sig = WasmOpcodes::Signature(opcode);
     if (!sig) sig = WasmOpcodes::AsmjsSignature(opcode);
     if (sig) return {sig->parameter_count(), sig->return_count()};
+    if (WasmOpcodes::IsPrefixOpcode(opcode)) {
+      opcode = static_cast<WasmOpcode>(opcode << 8 | *(pc + 1));
+    }
 
 #define DECLARE_OPCODE_CASE(name, opcode, sig) case kExpr##name:
     // clang-format off
     switch (opcode) {
       case kExprSelect:
         return {3, 1};
+      case kExprS128StoreMem:
       FOREACH_STORE_MEM_OPCODE(DECLARE_OPCODE_CASE)
         return {2, 0};
+      case kExprS128LoadMem:
       FOREACH_LOAD_MEM_OPCODE(DECLARE_OPCODE_CASE)
       case kExprTeeLocal:
       case kExprGrowMemory:
@@ -1229,10 +1237,6 @@ class WasmFullDecoder : public WasmDecoder {
           case kExprF64LoadMem:
             len = DecodeLoadMem(kWasmF64, MachineType::Float64());
             break;
-          case kExprS128LoadMem:
-            CHECK_PROTOTYPE_OPCODE(simd);
-            len = DecodeLoadMem(kWasmS128, MachineType::Simd128());
-            break;
           case kExprI32StoreMem8:
             len = DecodeStoreMem(kWasmI32, MachineType::Int8());
             break;
@@ -1260,10 +1264,6 @@ class WasmFullDecoder : public WasmDecoder {
           case kExprF64StoreMem:
             len = DecodeStoreMem(kWasmF64, MachineType::Float64());
             break;
-          case kExprS128StoreMem:
-            CHECK_PROTOTYPE_OPCODE(simd);
-            len = DecodeStoreMem(kWasmS128, MachineType::Simd128());
-            break;
           case kExprGrowMemory: {
             if (!CheckHasMemory()) break;
             MemoryIndexOperand<true> operand(this, pc_);
@@ -1506,6 +1506,29 @@ class WasmFullDecoder : public WasmDecoder {
     return 1 + operand.length;
   }
 
+  int DecodePrefixedLoadMem(ValueType type, MachineType mem_type) {
+    if (!CheckHasMemory()) return 0;
+    MemoryAccessOperand<true> operand(
+        this, pc_ + 1, ElementSizeLog2Of(mem_type.representation()));
+
+    Value index = Pop(0, kWasmI32);
+    TFNode* node = BUILD(LoadMem, type, mem_type, index.node, operand.offset,
+                         operand.alignment, position());
+    Push(type, node);
+    return operand.length;
+  }
+
+  int DecodePrefixedStoreMem(ValueType type, MachineType mem_type) {
+    if (!CheckHasMemory()) return 0;
+    MemoryAccessOperand<true> operand(
+        this, pc_ + 1, ElementSizeLog2Of(mem_type.representation()));
+    Value val = Pop(1, type);
+    Value index = Pop(0, kWasmI32);
+    BUILD(StoreMem, mem_type, index.node, operand.offset, operand.alignment,
+          val.node, position());
+    return operand.length;
+  }
+
   unsigned SimdExtractLane(WasmOpcode opcode, ValueType type) {
     SimdLaneOperand<true> operand(this, pc_);
     if (Validate(pc_, opcode, operand)) {
@@ -1591,6 +1614,14 @@ class WasmFullDecoder : public WasmDecoder {
         len = Simd8x16ShuffleOp();
         break;
       }
+      case kExprS128LoadMem:
+        CHECK_PROTOTYPE_OPCODE(simd);
+        len = DecodePrefixedLoadMem(kWasmS128, MachineType::Simd128());
+        break;
+      case kExprS128StoreMem:
+        CHECK_PROTOTYPE_OPCODE(simd);
+        len = DecodePrefixedStoreMem(kWasmS128, MachineType::Simd128());
+        break;
       default: {
         FunctionSig* sig = WasmOpcodes::Signature(opcode);
         if (sig != nullptr) {