[x64] Fix instruction selection for Word64Equal(Word64And, 0).

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 <algorithm>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
@@ skipping 1295 matching lines @@
         return VisitWordCompare(this, value, kX64Cmp32, &cont);
       case IrOpcode::kInt32LessThanOrEqual:
         cont.OverwriteAndNegateIfEqual(kSignedLessThanOrEqual);
         return VisitWordCompare(this, value, kX64Cmp32, &cont);
       case IrOpcode::kUint32LessThan:
         cont.OverwriteAndNegateIfEqual(kUnsignedLessThan);
         return VisitWordCompare(this, value, kX64Cmp32, &cont);
       case IrOpcode::kUint32LessThanOrEqual:
         cont.OverwriteAndNegateIfEqual(kUnsignedLessThanOrEqual);
         return VisitWordCompare(this, value, kX64Cmp32, &cont);
-      case IrOpcode::kWord64Equal:
+      case IrOpcode::kWord64Equal: {
         cont.OverwriteAndNegateIfEqual(kEqual);
+        Int64BinopMatcher m(value);
+        if (m.right().Is(0)) {
+          // Try to combine the branch with a comparison.
+          Node* const user = m.node();
+          Node* const value = m.left().node();

[Jarin, 2015/06/24 07:35:59]

Could you avoid shadowing the 'user' and 'value' variables from above?

[Benedikt Meurer, 2015/06/24 07:38:18]

Done.

+          if (CanCover(user, value)) {
+            switch (value->opcode()) {
+              case IrOpcode::kInt64Sub:
+                return VisitWord64Compare(this, value, &cont);
+              case IrOpcode::kWord64And:
+                return VisitWordCompare(this, value, kX64Test, &cont);
+              default:
+                break;
+            }
+          }
+          return VisitCompareZero(this, value, kX64Cmp, &cont);
+        }
         return VisitWord64Compare(this, value, &cont);
+      }
       case IrOpcode::kInt64LessThan:
         cont.OverwriteAndNegateIfEqual(kSignedLessThan);
         return VisitWord64Compare(this, value, &cont);
       case IrOpcode::kInt64LessThanOrEqual:
         cont.OverwriteAndNegateIfEqual(kSignedLessThanOrEqual);
         return VisitWord64Compare(this, value, &cont);
       case IrOpcode::kUint64LessThan:
         cont.OverwriteAndNegateIfEqual(kUnsignedLessThan);
         return VisitWord64Compare(this, value, &cont);
       case IrOpcode::kFloat32Equal:
@@ skipping 142 matching lines @@
 }
 
 
 void InstructionSelector::VisitUint32LessThanOrEqual(Node* node) {
   FlagsContinuation cont(kUnsignedLessThanOrEqual, node);
   VisitWordCompare(this, node, kX64Cmp32, &cont);
 }
 
 
 void InstructionSelector::VisitWord64Equal(Node* const node) {
-  Node* user = node;
   FlagsContinuation cont(kEqual, node);
-  Int64BinopMatcher m(user);
+  Int64BinopMatcher m(node);
   if (m.right().Is(0)) {
-    Node* value = m.left().node();
-
-    // Try to combine with comparisons against 0 by simply inverting the branch.
-    while (CanCover(user, value) && value->opcode() == IrOpcode::kWord64Equal) {
-      Int64BinopMatcher m(value);
-      if (m.right().Is(0)) {
-        user = value;
-        value = m.left().node();
-        cont.Negate();
-      } else {
-        break;
-      }
-    }
-
-    // Try to combine the branch with a comparison.
+    // Try to combine the equality check with a comparison.
+    Node* const user = m.node();
+    Node* const value = m.left().node();
     if (CanCover(user, value)) {
       switch (value->opcode()) {
         case IrOpcode::kInt64Sub:
           return VisitWord64Compare(this, value, &cont);
         case IrOpcode::kWord64And:
           return VisitWordCompare(this, value, kX64Test, &cont);
         default:
           break;
       }
     }
-    return VisitCompareZero(this, value, kX64Cmp, &cont);
   }
   VisitWord64Compare(this, node, &cont);
 }
 
 
 void InstructionSelector::VisitInt32AddWithOverflow(Node* node) {
   if (Node* ovf = NodeProperties::FindProjection(node, 1)) {
     FlagsContinuation cont(kOverflow, ovf);
     VisitBinop(this, node, kX64Add32, &cont);
   }
@@ skipping 115 matching lines @@
   if (CpuFeatures::IsSupported(SSE4_1)) {
     flags |= MachineOperatorBuilder::kFloat64RoundDown |
              MachineOperatorBuilder::kFloat64RoundTruncate;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8