[Bug rtl-optimization/21182] [4.6/4.7/4.8 Regression] gcc can use registers but uses stack instead

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21182

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vmakarov at gcc dot gnu.org
   Target Milestone|---                         |4.6.4
            Summary|gcc can use registers but   |[4.6/4.7/4.8 Regression]
                   |uses stack instead          |gcc can use registers but
                   |                            |uses stack instead

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> 2013-01-18 10:38:54 UTC ---
4.4.7 and 4.5.4 generate the same code (no stack use) for -D/-UNAIL_REGS.
With 4.6.3, the -DNAIL_REGS code regresses very much (IRA ...), the
-UNAIL_REGS code is nearly perfect but less good than 4.4/4.5 (if you
only consider grep esp serpent.s | wc -l).  Same behavior with 4.7.2.

Trunk got somewhat worse with -UNAIL_REGS but better with -DNAIL_REGS (at -O2):

     -UNAIL_REGS  -DNAIL_REGS
4.5.4     3             3
4.6.3    15           101
4.7.2    15            93
4.8.0    23            70

The most important thing to fix is the -UNAIL_REGS case of course.

A regression for that from 4.4/4.5.