[Bug rtl-optimization/57968] New: MODE_EXIT switches inserted too late

[Bug rtl-optimization/57968] New: MODE_EXIT switches inserted too late

[amylaar at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57968

            Bug ID: 57968
           Summary: MODE_EXIT switches inserted too late
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amylaar at gcc dot gnu.org

I see a miscompilation of ___muldi3 for epiphany-elf; the witch to MODE_EXIT
is done at the start of the exit block, even though it contains instructions
that require a different mode.

The return register on the epiphany is not likely spilled, and a large register
file gives lots of freedom to do optimizations; when optimizig ___muldi3, at
end end the return value is not so much copied as calculated piecemeal.

There is some existing code in compute_pre_exit that is supposed to preserve
computations that need a non-exit mode, but the way it is placed means it is
only active when the immediate result is part of the return register.

[Bug rtl-optimization/57968] MODE_EXIT switches inserted too early

[amylaar at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57968

--- Comment #1 from Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> ---
A patch is here:
http://gcc.gnu.org/ml/gcc-patches/2013-07/msg01081.html

[Bug rtl-optimization/57968] MODE_EXIT switches inserted too early

[chrbr at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57968

chrbr at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |chrbr at gcc dot gnu.org

--- Comment #2 from chrbr at gcc dot gnu.org ---
Created attachment 30571
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30571&action=edit
Same issue on SH4

Same problem with the attached test on 4.8.1 SH4 whereas I also see the EXIT
block inserted before the FP use.

Testing with your patch on 4.8

[Bug rtl-optimization/57968] MODE_EXIT switches inserted too early

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57968

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
   Target Milestone|---                         |4.9.0
         Resolution|---                         |FIXED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed a long time ago: r0-124444-gce4a94223ea08c (for GCC 4.9.0).