Tweak the Better{Left,Right}Operand() heuristic

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 2bfb284f829fcd1fad85f37d9e888c1c0ee851d2..e209ffb27d1f58b4344581d588ef906882ea6f74 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -967,6 +967,7 @@ class HValue : public ZoneObject {
   Representation RepresentationFromUses();
   Representation RepresentationFromUseRequirements();
   bool HasNonSmiUse();
+  bool UsedBy(HValue* value);
   virtual void UpdateRepresentation(Representation new_rep,
                                     HInferRepresentationPhase* h_infer,
                                     const char* reason);
@@ -3545,8 +3546,17 @@ class HBinaryOperation : public HTemplateInstruction<3> {
 
     // Constant operands are better off on the right, they can be inlined in
     // many situations on most platforms.
-    if (left()->IsConstant()) return true;
-    if (right()->IsConstant()) return false;
+    if (left()->IsConstant() &&
+        (!representation().IsDouble() || left()->UseCount() > 1)) {
+      return true;
+    }
+    if (right()->IsConstant() &&
+        (!representation().IsDouble() || right()->UseCount() > 1)) {
+      return false;
+    }
+
+    if (left()->IsPhi() && UsedBy(left())) return false;
+    if (right()->IsPhi() && UsedBy(right())) return true;
 

[haitao.feng, 2014/05/15 05:56:20]

How about writing codes in this way?
-    if (left()->IsConstant()) return true;
-    if (right()->IsConstant()) return false;
+    if (left()->IsConstant() && left()->EmitAtUses()) return true;
+    if (right()->IsConstant() && right()->EmitAtUses()) return false;
+
+    // If destination is one operand of the phi node, they might be allocated
+    // to the same register by hinting.
+    if (left()->IsPhi()) {
+      HPhi* phi = HPhi::cast(left());
+      for (int i = 0; i < phi->OperandCount(); i++) {
+        if (phi->OperandAt(i) == this) return false;
+      }
+    } else if (right()->IsPhi()) {
+      HPhi* phi = HPhi::cast(right());
+      for (int i = 0; i < phi->OperandCount(); i++) {
+        if (phi->OperandAt(i) == this) return true;
+      }
+    }

     // Otherwise, if there is only one use of the right operand, it would be
     // better off on the left for platforms that only have 2-arg arithmetic