[Bug rtl-optimization/72855] Long compile time due to integrity checking during dataflow analysis per loop

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72855

amker at gcc dot gnu.org changed:

           What    |Removed                     |Added
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                 CC|                            |amker at gcc dot gnu.org

--- Comment #1 from amker at gcc dot gnu.org ---
Among all loops in the large function, how many loops can be doloop optimized
successfully?  Function doloop__optimize has some valid checks on doloop
optimizations.  Is it possible to move most (some) of checks outside of the
per-loop function.  Looks like targetm.invalid_within_doloop can be moved.  As
a result, we can know some loops can't be doloop optimized, so the
iv_analysis/df_analysis can be skipped for those loops.  For checks on loop
analysis result:
  if (!desc->simple_p
      || desc->assumptions
      || desc->infinite)
I think it's possible to avoid per-loop analysis behavior too.  Since we don't
change code, there is no need to do df analysis for each loop before
iv_analysis.  As a result, df_verify can be saved.  We may need a new interface
analyzing iv/loop_desc for all loops in loop-iv.c

Of course, if most loops can be doloop optimized, this may not be able to help.