Fix problem with GenericBinaryOperationStub::GenerateCall for a Smi...

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
===================================================================
--- src/x64/codegen-x64.cc	(revision 3833)
+++ src/x64/codegen-x64.cc	(working copy)
@@ -8051,6 +8051,8 @@
         }
       } else if (left.is(left_arg)) {
         __ movq(right_arg, right);
+      } else if (right.is(right_arg)) {
+        __ movq(left_arg, left);
       } else if (left.is(right_arg)) {
         if (IsOperationCommutative()) {
           __ movq(left_arg, right);
@@ -8069,8 +8071,6 @@
           __ movq(right_arg, right);
           __ movq(left_arg, left);
         }
-      } else if (right.is(right_arg)) {
-        __ movq(left_arg, left);
       } else {
         // Order of moves is not important.
         __ movq(left_arg, left);
@@ -8106,6 +8106,10 @@
       __ Move(left_arg, right);
       SetArgsReversed();
     } else {
+      // For non-commutative operations, left and right_arg might be
+      // the same register.  Therefore, the order of the moves is
+      // important here in order to not overwrite left before moving
+      // it to left_arg.
       __ movq(left_arg, left);
       __ Move(right_arg, right);
     }
@@ -8138,8 +8142,12 @@
       __ Move(right_arg, left);
       SetArgsReversed();
     } else {
+      // For non-commutative operations, right and left_arg might be
+      // the same register.  Therefore, the order of the moves is
+      // important here in order to not overwrite right before moving
+      // it to right_arg.
+      __ movq(right_arg, right);
       __ Move(left_arg, left);
-      __ movq(right_arg, right);
     }
     // Update flags to indicate that arguments are in registers.
     SetArgsInRegisters();