[PATCH, i386]: Improve STV convert gain function when shifts are involved

[Uros Bizjak]

2017-04-11  Uros Bizjak  <ubiz...@gmail.com>

    * config/i386/i386.c (dimode_scalar_chain::compute_convert_gain):
    Use shift_const cost parameter when calculating gain of STV shifts.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Committed to mainline SVN.

Uros.

Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c  (revision 246843)
+++ config/i386/i386.c  (working copy)
@@ -3407,7 +3407,7 @@ dimode_scalar_chain::compute_convert_gain ()
       else if (GET_CODE (src) == ASHIFT
               || GET_CODE (src) == LSHIFTRT)
        {
-         gain += ix86_cost->add;
+         gain += ix86_cost->shift_const;
          if (CONST_INT_P (XEXP (src, 0)))
            gain -= vector_const_cost (XEXP (src, 0));
          if (CONST_INT_P (XEXP (src, 1))