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

src/compiler/instruction-selector-impl.h

 // 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.
 
 #ifndef V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_
 #define V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_
 
 #include "src/compiler/generic-node-inl.h"
 #include "src/compiler/instruction.h"
 #include "src/compiler/instruction-selector.h"
@@ skipping 239 matching lines @@
     DCHECK(IsBranch());
     return true_block_;
   }
   BasicBlock* false_block() const {
     DCHECK(IsBranch());
     return false_block_;
   }
 
   void Negate() {
     DCHECK(!IsNone());
-    condition_ = static_cast<FlagsCondition>(condition_ ^ 1);
+    condition_ = NegateFlagsCondition(condition_);
   }
 
   void Commute() {
     DCHECK(!IsNone());
     switch (condition_) {
       case kEqual:
       case kNotEqual:
       case kOverflow:
       case kNotOverflow:
         return;
@@ skipping 39 matching lines @@
     }
     UNREACHABLE();
   }
 
   void OverwriteAndNegateIfEqual(FlagsCondition condition) {
     bool negate = condition_ == kEqual;
     condition_ = condition;
     if (negate) Negate();
   }
 
-  void SwapBlocks() { std::swap(true_block_, false_block_); }
-
   // Encodes this flags continuation into the given opcode.
   InstructionCode Encode(InstructionCode opcode) {
     opcode |= FlagsModeField::encode(mode_);
     if (mode_ != kFlags_none) {
       opcode |= FlagsConditionField::encode(condition_);
     }
     return opcode;
   }
 
  private:
@@ skipping 29 matching lines @@
                : (frame_state_descriptor->GetTotalSize() +
                   1);  // Include deopt id.
   }
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_SELECTOR_IMPL_H_