[wasm] Add a BytecodeIterator and use in non-performance-critical situations.

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

Index: test/unittests/wasm/ast-decoder-unittest.cc
diff --git a/test/unittests/wasm/ast-decoder-unittest.cc b/test/unittests/wasm/ast-decoder-unittest.cc
index 889cfb1b1a3ed1695f729675aafc22a5f5acd37f..05a0e95f6a73e5c87a644d1a1f2a5c88eebc497e 100644
--- a/test/unittests/wasm/ast-decoder-unittest.cc
+++ b/test/unittests/wasm/ast-decoder-unittest.cc
@@ -2437,6 +2437,60 @@ TEST_F(LocalDeclDecoderTest, UseEncoder) {
   pos = ExpectRun(map, pos, kAstI64, 212);
 }
 
+class BytecodeIteratorTest : public TestWithZone {};
+
+TEST_F(BytecodeIteratorTest, SimpleForeach) {
+  byte code[] = {WASM_IF_ELSE(WASM_ZERO, WASM_ZERO, WASM_ZERO)};
+  BytecodeIterator iter(code, code + sizeof(code));
+  WasmOpcode expected[] = {kExprI8Const, kExprIf,      kExprI8Const,
+                           kExprElse,    kExprI8Const, kExprEnd};
+  size_t pos = 0;
+  for (WasmOpcode opcode : iter) {
+    if (pos >= arraysize(expected)) {
+      EXPECT_TRUE(false);

[ahaas, 2016/07/11 12:31:19]

why don't you say 
EXPECT_TRUE(pos < arraysize(expected));?

+      break;
+    }
+    EXPECT_EQ(expected[pos++], opcode);
+  }
+  EXPECT_EQ(arraysize(expected), pos);
+}
+
+TEST_F(BytecodeIteratorTest, ForeachTwice) {
+  byte code[] = {WASM_IF_ELSE(WASM_ZERO, WASM_ZERO, WASM_ZERO)};
+  BytecodeIterator iter(code, code + sizeof(code));
+  int count = 0;
+
+  count = 0;
+  for (WasmOpcode opcode : iter) {
+    USE(opcode);
+    count++;
+  }
+  EXPECT_EQ(6, count);
+
+  count = 0;
+  for (WasmOpcode opcode : iter) {
+    USE(opcode);
+    count++;
+  }
+  EXPECT_EQ(6, count);
+}
+
+TEST_F(BytecodeIteratorTest, WithAstDecls) {
+  byte code[] = {1, 1, kLocalI32, WASM_I8(9), WASM_I8(11)};
+  AstLocalDecls decls(zone());
+  BytecodeIterator iter(code, code + sizeof(code), &decls);
+
+  EXPECT_EQ(3, decls.decls_encoded_size);
+  EXPECT_EQ(3, iter.pc_offset());
+  EXPECT_TRUE(iter.has_next());
+  EXPECT_EQ(kExprI8Const, iter.current());
+  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