[Bug tree-optimization/24123] [4.1 Regression] Massive performance regression for -ffast-math due to the recip tree pass

[bonzini at gcc dot gnu dot org]

------- Additional Comments From bonzini at gcc dot gnu dot org  2005-09-30 10:15 -------
To calculate the numbers I gave you,  I took the sum of the percentages in the
profiling snippets, and the cumulative time for the last line of the profiling
snippets.  Then pct * 100 / time obviously gives you the total running time.

The original bug report gives the -fno-fast-math timing
  top functions account for 28.3%, seconds = 4.34 --> total time = 15.33

Comment #4 gives the timing with -ffast-math but without recip:
  top functions account for 44.94%, seconds = 6.93 --> total time = 14.21

Comment #6 gives the times with -ffast-math and the new recip:
  top functions account for 37.96%, seconds = 5.97 --> total time = 13.88

So it seems that the patch introduces a speedup.  If not, can you provide
profiling output for the two povray's in comment %9 (either on abyss.pov, or on
the standard POVray benchmark)?

Thanks,

Paolo

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24123