[wasm] Canonicalize function signature indices for matching in indirect calls.

src/wasm/wasm-module-builder.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_WASM_WASM_MODULE_BUILDER_H_
 #define V8_WASM_WASM_MODULE_BUILDER_H_
 
 #include "src/signature.h"
 #include "src/zone/zone-containers.h"
 
@@ skipping 204 matching lines @@
   uint32_t AddGlobal(LocalType type, bool exported, bool mutability = true,
                      const WasmInitExpr& init = WasmInitExpr());
   void AddDataSegment(const byte* data, uint32_t size, uint32_t dest);
   uint32_t AddSignature(FunctionSig* sig);
   void AddIndirectFunction(uint32_t index);
   void MarkStartFunction(WasmFunctionBuilder* builder);
 
   // Writing methods.
   void WriteTo(ZoneBuffer& buffer) const;
 
+  // TODO(titzer): use SignatureMap from signature-map.h here.
+  // This signature map is zone-allocated, but the other is heap allocated.
   struct CompareFunctionSigs {
     bool operator()(FunctionSig* a, FunctionSig* b) const;
   };
   typedef ZoneMap<FunctionSig*, uint32_t, CompareFunctionSigs> SignatureMap;
 
   Zone* zone() { return zone_; }
 
   FunctionSig* GetSignature(uint32_t index) { return signatures_[index]; }
 
  private:
@@ skipping 29 matching lines @@
 
 inline FunctionSig* WasmFunctionBuilder::signature() {
   return builder_->signatures_[signature_index_];
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_WASM_MODULE_BUILDER_H_