[Bug rtl-optimization/77287] Much worse code generated compared to clang (stack alignment and spills)

rguenth at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Thu Aug 18 12:02:00 GMT 2016


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77287

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ra
             Target|                            |x86_64-*-*, i?86-*-*
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-08-18
                 CC|                            |vmakarov at gcc dot gnu.org
          Component|target                      |rtl-optimization
     Ever confirmed|0                           |1

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
-fschedule-insns improves things here - and LRA seems to be more happy to
spill/reload rather than rematerialize.  But in the end the testcase requires
careful scheduling of the operations to reduce register lifetime and thus
allow optimal RA with the limited number of registers available.

We force a frame pointer because we have to re-align the stack for possible
spills.


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