[wasm] Add some tests for control flow corner cases.

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/cctest/wasm/test-signatures.h"
 
@@ skipping 496 matching lines @@
 
 TEST_F(AstDecoderTest, BlockBinop) {
   EXPECT_VERIFIES_INLINE(sigs.i_i(), WASM_I32_AND(B1(WASM_I8(1)), WASM_I8(2)));
 }
 
 TEST_F(AstDecoderTest, BlockBrBinop) {
   EXPECT_VERIFIES_INLINE(sigs.i_i(),
                          WASM_I32_AND(B1(WASM_BRV(0, WASM_I8(1))), WASM_I8(2)));
 }
 
+TEST_F(AstDecoderTest, If_empty1) {
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_ZERO, kExprIf, kExprEnd);
+}
+
+TEST_F(AstDecoderTest, If_empty2) {
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_ZERO, kExprIf, kExprElse, kExprEnd);
+}
+
+TEST_F(AstDecoderTest, If_empty3) {
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_ZERO, kExprIf, WASM_ZERO, kExprElse,
+                         kExprEnd);
+}
+
+TEST_F(AstDecoderTest, If_empty4) {
+  EXPECT_VERIFIES_INLINE(sigs.v_v(), WASM_ZERO, kExprIf, kExprElse, WASM_ZERO,
+                         kExprEnd);
+}
+
 TEST_F(AstDecoderTest, If_empty_stack) {
   byte code[] = {kExprIf};
   EXPECT_FAILURE(sigs.v_v(), code);
   EXPECT_FAILURE(sigs.i_i(), code);
 }
 
 TEST_F(AstDecoderTest, If_incomplete1) {
   byte code[] = {kExprI8Const, 0, kExprIf};
   EXPECT_FAILURE(sigs.v_v(), code);
   EXPECT_FAILURE(sigs.i_i(), code);
@@ skipping 1909 matching lines @@
   size_t pos = 0;
   pos = ExpectRun(map, pos, kAstF32, 5);
   pos = ExpectRun(map, pos, kAstI32, 1337);
   pos = ExpectRun(map, pos, kAstI64, 212);
   delete[] data;
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8