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

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

Index: src/compiler/x64/instruction-selector-x64.cc
diff --git a/src/compiler/x64/instruction-selector-x64.cc b/src/compiler/x64/instruction-selector-x64.cc
index c841acebc0667ea95086a3c29a825650f70d1643..839af8e45542dd64bcf7ab157decf681da805527 100644
--- a/src/compiler/x64/instruction-selector-x64.cc
+++ b/src/compiler/x64/instruction-selector-x64.cc
@@ -1313,9 +1313,27 @@ void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
       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);
@@ -1478,25 +1496,12 @@ void InstructionSelector::VisitUint32LessThanOrEqual(Node* node) {
 
 
 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:
@@ -1507,7 +1512,6 @@ void InstructionSelector::VisitWord64Equal(Node* const node) {
           break;
       }
     }
-    return VisitCompareZero(this, value, kX64Cmp, &cont);
   }
   VisitWord64Compare(this, node, &cont);
 }