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

src/wasm/signature-map.cc

+// Copyright 2016 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 "src/wasm/signature-map.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+uint32_t SignatureMap::Get(FunctionSig* sig) {

[ahaas, 2016/10/11 09:20:09]

I think the name {Get} is misleading because typically get-function do not
change the state. What about {FindOrInsert}?

[titzer, 2016/10/11 11:58:31]

Done.

+  auto pos = map_.find(sig);
+  if (pos != map_.end()) {
+    return pos->second;
+  } else {
+    uint32_t index = next_++;
+    map_[sig] = index;
+    return index;
+  }
+}
+
+int32_t SignatureMap::Find(FunctionSig* sig) const {
+  auto pos = map_.find(sig);
+  if (pos != map_.end()) {
+    return static_cast<int32_t>(pos->second);
+  } else {
+    return -1;
+  }
+}
+
+bool SignatureMap::CompareFunctionSigs::operator()(FunctionSig* a,
+                                                   FunctionSig* b) const {
+  if (a == b) return false;
+  if (a->return_count() < b->return_count()) return true;
+  if (a->return_count() > b->return_count()) return false;
+  if (a->parameter_count() < b->parameter_count()) return true;
+  if (a->parameter_count() > b->parameter_count()) return false;
+  for (size_t r = 0; r < a->return_count(); r++) {
+    if (a->GetReturn(r) < b->GetReturn(r)) return true;
+    if (a->GetReturn(r) > b->GetReturn(r)) return false;
+  }
+  for (size_t p = 0; p < a->parameter_count(); p++) {
+    if (a->GetParam(p) < b->GetParam(p)) return true;
+    if (a->GetParam(p) > b->GetParam(p)) return false;
+  }
+  return false;
+}
+
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8