[wasm] Implement parallel compilation.

src/compiler/wasm-compiler.h

 // 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.
 
 #ifndef V8_COMPILER_WASM_COMPILER_H_
 #define V8_COMPILER_WASM_COMPILER_H_
 
 // Clients of this interface shouldn't depend on lots of compiler internals.
 // Do not include anything from src/compiler here!
 #include "src/wasm/wasm-opcodes.h"
@@ skipping 80 matching lines @@
   Node* Loop(Node* entry);
   Node* Terminate(Node* effect, Node* control);
   Node* Merge(unsigned count, Node** controls);
   Node* Phi(wasm::LocalType type, unsigned count, Node** vals, Node* control);
   Node* EffectPhi(unsigned count, Node** effects, Node* control);
   Node* NumberConstant(int32_t value);
   Node* Int32Constant(int32_t value);
   Node* Int64Constant(int64_t value);
   Node* Float32Constant(float value);
   Node* Float64Constant(double value);
-  Node* Constant(Handle<Object> value);
+  Node* HeapConstant(Handle<HeapObject> value);
   Node* Binop(wasm::WasmOpcode opcode, Node* left, Node* right,
               wasm::WasmCodePosition position = wasm::kNoCodePosition);
   Node* Unop(wasm::WasmOpcode opcode, Node* input,
              wasm::WasmCodePosition position = wasm::kNoCodePosition);
   unsigned InputCount(Node* node);
   bool IsPhiWithMerge(Node* phi, Node* merge);
   void AppendToMerge(Node* merge, Node* from);
   void AppendToPhi(Node* phi, Node* from);
 
   //-----------------------------------------------------------------------
@@ skipping 193 matching lines @@
     Node** buf = Buffer(new_count);
     if (buf != buffer) memcpy(buf, buffer, old_count * sizeof(Node*));
     return buf;
   }
 };
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_WASM_COMPILER_H_