[turbofan] Clean up and factor out branch generation logic.

src/compiler/x64/instruction-selector-x64.cc

 // Copyright 2014 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/generic-node-inl.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 881 matching lines @@
 
 
 void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
                                       BasicBlock* fbranch) {
   X64OperandGenerator g(this);
   Node* user = branch;
   Node* value = branch->InputAt(0);
 
   FlagsContinuation cont(kNotEqual, tbranch, fbranch);
 
-  // If we can fall through to the true block, invert the branch.
-  if (IsNextInAssemblyOrder(tbranch)) {
-    cont.Negate();
-    cont.SwapBlocks();
-  }
-
   // Try to combine with comparisons against 0 by simply inverting the branch.
   while (CanCover(user, value)) {
     if (value->opcode() == IrOpcode::kWord32Equal) {
       Int32BinopMatcher m(value);
       if (m.right().Is(0)) {
         user = value;
         value = m.left().node();
         cont.Negate();
       } else {
         break;
@@ skipping 253 matching lines @@
     return MachineOperatorBuilder::kFloat64Floor |
            MachineOperatorBuilder::kFloat64Ceil |
            MachineOperatorBuilder::kFloat64RoundTruncate;
   }
   return MachineOperatorBuilder::kNoFlags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8