VM: Optimize RegExp.matchAsPrefix(...) by generating a sticky RegExp specialization.

runtime/vm/raw_object.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_RAW_OBJECT_H_
 #define RUNTIME_VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/atomic.h"
 #include "vm/globals.h"
@@ skipping 2098 matching lines @@
 
 // VM type for capturing JS regular expressions.
 class RawRegExp : public RawInstance {
   RAW_HEAP_OBJECT_IMPLEMENTATION(RegExp);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->num_bracket_expressions_);
   }
   RawSmi* num_bracket_expressions_;
   RawString* pattern_;  // Pattern to be used for matching.
-  RawFunction* one_byte_function_;
-  RawFunction* two_byte_function_;
+  union {
+    RawFunction* function_;
+    RawTypedData* bytecode_;
+  } one_byte_;
+  union {
+    RawFunction* function_;
+    RawTypedData* bytecode_;
+  } two_byte_;
   RawFunction* external_one_byte_function_;
   RawFunction* external_two_byte_function_;
-  RawTypedData* one_byte_bytecode_;
-  RawTypedData* two_byte_bytecode_;
+  union {
+    RawFunction* function_;
+    RawTypedData* bytecode_;
+  } one_byte_sticky_;
+  union {
+    RawFunction* function_;
+    RawTypedData* bytecode_;
+  } two_byte_sticky_;
+  RawFunction* external_one_byte_sticky_function_;
+  RawFunction* external_two_byte_sticky_function_;
   RawObject** to() {
-    return reinterpret_cast<RawObject**>(&ptr()->two_byte_bytecode_);
+    return reinterpret_cast<RawObject**>(
+        &ptr()->external_two_byte_sticky_function_);
   }
 
   intptr_t num_registers_;
 
   // A bitfield with two fields:
   // type: Uninitialized, simple or complex.
   // flags: Represents global/local, case insensitive, multiline.
   int8_t type_flags_;
 };
 
@@ skipping 240 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_RAW_OBJECT_H_