[v8-dev] ARM: Improve Lithium register constraints.

src/hydrogen-instructions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3460 matching lines @@
 
   // True if switching left and right operands likely generates better code.
   bool AreOperandsBetterSwitched() {
     if (!IsCommutative()) return false;
 
     // 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;
 
+#ifdef V8_BETTER_OPERAND_ON_RIGHT
+    // Otherwise, if there is only one use of the left operand, the define
+    // says it would be better off on the right.
+    return (left()->UseCount() == 1);
+#else
     // 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
     // ops (e.g ia32, x64) that clobber the left operand.
     return right()->UseCount() == 1;
+#endif
   }
 
   HValue* BetterLeftOperand() {
     return AreOperandsBetterSwitched() ? right() : left();
   }
 
   HValue* BetterRightOperand() {
     return AreOperandsBetterSwitched() ? left() : right();
   }
 
@@ skipping 3286 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_