patch to fix PR56999

[Vladimir Makarov <vmakarov at redhat dot com>]

  The following patch fixes

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56999

  The problem was in complicated interactions of coalescing and 
doing/undoing inheritance and assignment sub-passes through several 
iterations.  One solution would be in modifying coalescing in order to 
take future actions in undoing inheritance.  Another solution is to move 
coalesce pass after doing/undoing inheritance sub-passes.  The first 
solution complicates code and make passes more dependable although 
potentially decreasing # passes of creating live ranges.  The second 
solution makes coalescing pass simpler and less dependable.  After some 
experiments I've chosen the 2nd solution as it makes code more 
maintainable and less error-prone.  On my tests I found that in 32-bit 
mode it runs 10% more  live-range passes (that is about 1/5th of LRA run 
time), in 64-bit mode the # passes are the same.  I check cpu and real 
time on 500K lines fortran code and did not find any visible increase in 
compilation time.

  The patch was successfully bootstrapped on x86-64.

  Committed to trunk as rev. 198092.

2013-04-18  Vladimir Makarov  <vmakarov@redhat.com>

        PR rtl-optimization/56992
        * lra-coalesce.c (coalescable_pseudo_p): Remove 2nd parameter and
        related code.
        (lra_coalesce): Remove split_origin_bitmap and related code.
        * lra.c (lra): Coalesce after undoing inheritance. Recreate live
        ranges if necessary.

2013-04-18  Jakub Jelinek  <jakub@redhat.com>

        PR rtl-optimization/56992
        * g++.dg/opt/pr56999.C: New test.

Attachment: pr56999.patch
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