[turbofan] Also update the BranchHint when merging a BooleanNot.

src/compiler/common-operator-reducer.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/common-operator-reducer.h"
 
 #include <algorithm>
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
@@ skipping 81 matching lines @@
           use->set_op(common()->IfTrue());
           break;
         default:
           UNREACHABLE();
       }
     }
     // Update the condition of {branch}. No need to mark the uses for revisit,
     // since we tell the graph reducer that the {branch} was changed and the
     // graph reduction logic will ensure that the uses are revisited properly.
     node->ReplaceInput(0, cond->InputAt(0));
+    // Negative the hint for {branch}.

[Sven Panne, 2015/06/26 11:40:56]

Why do we need the switch at all? Isn't the simple one-liner

  node->set_op(common()->Branch(NegateBranch(BranchHintOf(node->op()));

enough for all cases? Then comment would be superfluous, BTW. If it's a
nano-optimization, please add a comment why it's necessary.

[Benedikt Meurer, 2015/06/26 11:43:40]

Done.

+    switch (BranchHintOf(node->op())) {
+      case BranchHint::kTrue:
+        node->set_op(common()->Branch(BranchHint::kFalse));
+        break;
+      case BranchHint::kFalse:
+        node->set_op(common()->Branch(BranchHint::kTrue));
+        break;
+      case BranchHint::kNone:
+        break;
+    }
     return Changed(node);
   }
   Decision const decision = DecideCondition(cond);
   if (decision == Decision::kUnknown) return NoChange();
   Node* const control = node->InputAt(1);
   for (Node* const use : node->uses()) {
     switch (use->opcode()) {
       case IrOpcode::kIfTrue:
         Replace(use, (decision == Decision::kTrue) ? control : dead());
         break;
@@ skipping 260 matching lines @@
   node->set_op(op);
   node->ReplaceInput(0, a);
   node->ReplaceInput(1, b);
   node->TrimInputCount(2);
   return Changed(node);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8