[wasm] Introduce custom asm.js bytecodes for double->int conversions.

src/wasm/asm-wasm-builder.cc

 // 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.
 
 #include "src/v8.h"
 
 // Required to get M_E etc. in MSVC.
 #if defined(_WIN32)
 #define _USE_MATH_DEFINES
 #endif
@@ skipping 1419 matching lines @@
         current_function_builder_->Emit(kExprF64UConvertI32);
       } else if (type == kFloat32) {
         current_function_builder_->Emit(kExprF64ConvertF32);
       } else {
         UNREACHABLE();
       }
     } else if (convertOperation == kToInt) {
       RECURSE(Visit(GetLeft(expr)));
       TypeIndex type = TypeIndexOf(GetLeft(expr));
       if (type == kFloat32) {
-        current_function_builder_->Emit(kExprI32SConvertF32);
+        current_function_builder_->Emit(kExprI32AsmjsSConvertF32);
       } else if (type == kFloat64) {
-        current_function_builder_->Emit(kExprI32SConvertF64);
+        current_function_builder_->Emit(kExprI32AsmjsSConvertF64);
       } else {
         UNREACHABLE();
       }
     } else if (convertOperation == kAsIs) {
       RECURSE(Visit(GetLeft(expr)));
     } else {
       if (expr->op() == Token::COMMA) {
         current_function_builder_->Emit(kExprBlock);
       }
 
@@ skipping 251 matching lines @@
 // that zone in constructor may be thrown away once wasm module is written.
 WasmModuleIndex* AsmWasmBuilder::Run() {
   AsmWasmBuilderImpl impl(isolate_, zone_, literal_, foreign_, typer_);
   impl.Compile();
   WasmModuleWriter* writer = impl.builder_->Build(zone_);
   return writer->WriteTo(zone_);
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8