[wasm] fix simd opcode read and error case for bad simd opcodes

test/unittests/wasm/ast-decoder-unittest.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "test/unittests/test-utils.h"
 
 #include "src/v8.h"
 
 #include "test/common/wasm/test-signatures.h"
 
@@ skipping 2482 matching lines @@
   EXPECT_LENGTH(1, kExprF64SConvertI32);
   EXPECT_LENGTH(1, kExprF64UConvertI32);
   EXPECT_LENGTH(1, kExprF64SConvertI64);
   EXPECT_LENGTH(1, kExprF64UConvertI64);
   EXPECT_LENGTH(1, kExprF64ConvertF32);
   EXPECT_LENGTH(1, kExprF64ReinterpretI64);
   EXPECT_LENGTH(1, kExprI32ReinterpretF32);
   EXPECT_LENGTH(1, kExprI64ReinterpretF64);
 }
 
+TEST_F(WasmOpcodeLengthTest, SimdExpressions) {
+#define TEST_SIMD(name, opcode, sig) \
+  EXPECT_LENGTH_N(2, kSimdPrefix, static_cast<byte>(kExpr##name & 0xff));
+  FOREACH_SIMD_0_OPERAND_OPCODE(TEST_SIMD)
+#undef TEST_SIMD
+#define TEST_SIMD(name, opcode, sig) \
+  EXPECT_LENGTH_N(3, kSimdPrefix, static_cast<byte>(kExpr##name & 0xff));
+  FOREACH_SIMD_1_OPERAND_OPCODE(TEST_SIMD)
+#undef TEST_SIMD
+  // test for bad simd opcode
+  EXPECT_LENGTH_N(2, kSimdPrefix, 0xff);
+}
+
 typedef ZoneVector<LocalType> LocalTypeMap;
 
 class LocalDeclDecoderTest : public TestWithZone {
  public:
   v8::internal::AccountingAllocator allocator;
 
   size_t ExpectRun(LocalTypeMap map, size_t pos, LocalType expected,
                    size_t count) {
     for (size_t i = 0; i < count; i++) {
       EXPECT_EQ(expected, map[pos++]);
@@ skipping 156 matching lines @@
   iter.next();
   EXPECT_TRUE(iter.has_next());
   EXPECT_EQ(kExprI8Const, iter.current());
   iter.next();
   EXPECT_FALSE(iter.has_next());
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8