[Bug target/50829] avx extra copy for _mm256_insertf128_pd

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50829

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|rtl-optimization            |target

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-11-24 03:43:46 UTC ---
The move that is generated in the split should be in the bigger mode.  And then
apply the following patch:
        * regrename.c (maybe_mode_change): Return the reg in the
        new mode if the copy was done in the same mode size.
Index: regrename.c
===================================================================
--- regrename.c    (revision 55954)
+++ regrename.c    (revision 55955)
@@ -1322,6 +1322,15 @@ maybe_mode_change (enum machine_mode ori
            enum machine_mode new_mode, unsigned int regno,
            unsigned int copy_regno ATTRIBUTE_UNUSED)
 {
+  /*  If we are using the register in the copy mode (if the number of hard
+      registers is the same), just used the reg with the new mode.  */
+  if (GET_MODE_SIZE (copy_mode) == GET_MODE_SIZE (new_mode)
+      && hard_regno_nregs[copy_regno][copy_mode] ==
+     hard_regno_nregs[copy_regno][new_mode]
+      && hard_regno_nregs[regno][copy_mode] ==
+     hard_regno_nregs[copy_regno][new_mode])
+    return gen_rtx_raw_REG (new_mode, regno);
+
   if (GET_MODE_SIZE (copy_mode) < GET_MODE_SIZE (orig_mode)
       && GET_MODE_SIZE (copy_mode) < GET_MODE_SIZE (new_mode))
     return NULL_RTX;

This will at least remove it with -frename-registers which we most likely
should have on by default at -O2 and above now anyways.