[wasm] Provide backoff implementations for the Fxx rounding instructions

src/compiler/fast-accessor-assembler.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/compiler/fast-accessor-assembler.h"
 
 #include "src/base/logging.h"
 #include "src/code-stubs.h"  // For CallApiFunctionStub.
 #include "src/compiler/graph.h"
 #include "src/compiler/linkage.h"
@@ skipping 149 matching lines @@
 void FastAccessorAssembler::CheckNotZeroOrJump(ValueId value_id,
                                                LabelId label_id) {
   CHECK_EQ(kBuilding, state_);
   RawMachineLabel pass;
   assembler_->Branch(
       assembler_->IntPtrEqual(FromId(value_id), assembler_->IntPtrConstant(0)),
       &pass, FromId(label_id));
   assembler_->Bind(&pass);
 }
 
-
 FastAccessorAssembler::ValueId FastAccessorAssembler::Call(
     FunctionCallback callback_function, ValueId arg) {
   CHECK_EQ(kBuilding, state_);
 
   // Create API function stub.
   CallApiFunctionStub stub(assembler_->isolate(), true);
 
   // Wrap the FunctionCallback in an ExternalReference.
   ApiFunction callback_api_function(FUNCTION_ADDR(callback_function));
   ExternalReference callback(&callback_api_function,
@@ skipping 21 matching lines @@
 
   Node* call = assembler_->CallN(
       Linkage::GetStubCallDescriptor(
           assembler_->isolate(), zone(), stub.GetCallInterfaceDescriptor(),
           kStackParam + stub.GetStackParameterCount(),
           CallDescriptor::kNoFlags),
       assembler_->HeapConstant(stub.GetCode()), args);
   return FromRaw(call);
 }
 
-
 MaybeHandle<Code> FastAccessorAssembler::Build() {
   CHECK_EQ(kBuilding, state_);
 
   // Cleanup: We no longer need this.
   nodes_.clear();
   labels_.clear();
 
   // Export the schedule and call the compiler.
   Schedule* schedule = assembler_->Export();
   Code::Flags flags = Code::ComputeFlags(Code::STUB);
@@ skipping 32 matching lines @@
 RawMachineLabel* FastAccessorAssembler::FromId(LabelId label) const {
   CHECK_LT(label.label_id, labels_.size());
   CHECK_NOT_NULL(labels_.at(label.label_id));
   return labels_.at(label.label_id);
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8