Move swapping of operands for commutative binary operations to the lithium IR...

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 6458)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -1183,8 +1183,12 @@
   if (instr->representation().IsInteger32()) {
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
-    LOperand* left = UseRegisterAtStart(instr->LeastConstantOperand());
-    LOperand* right = UseOrConstantAtStart(instr->MostConstantOperand());
+    LOperand* left = UseRegisterAtStart(instr->left()->IsConstant()
+                                        ? instr->right()
+                                        : instr->left());
+    LOperand* right = UseOrConstantAtStart(instr->left()->IsConstant()
+                                           ? instr->left()
+                                           : instr->right());
     LAddI* add = new LAddI(left, right);
     LInstruction* result = DefineSameAsFirst(add);
     if (instr->CheckFlag(HValue::kCanOverflow)) {