Gcc 3.1 performance regressions with respect to 2.95.3

[Peter Schmid]

I applied your cross jumping patch, did a full bootstrap and ran the
regression test suite. There are no regressions.

Here are the results for the stepanov test. Surprisingly, when the -O
optimization gains the most speed from your patch, resulting in the
fastest executable.  Now, gcc 3.1 has about the same performance as
gcc 2.95, but at the -O3 level. Why have the additional optimizations
no net effect in comparison to -O? Do you have an idea what is going wrong?

Thank you for enhancing the performance. I strongly suggest your patch
should go in.

Hope this helps,

Peter Schmid



-O
test      absolute   additions      ratio with
number    time       per second     test0

 0        0.45sec    111.11M         1.00
 1        0.46sec    108.70M         1.02
 2        0.46sec    108.70M         1.02
 3        0.45sec    111.11M         1.00
 4        0.48sec    104.17M         1.07
 5        0.53sec    94.34M         1.18
 6        0.50sec    100.00M         1.11
 7        0.50sec    100.00M         1.11
 8        0.51sec    98.04M         1.13
 9        0.46sec    108.70M         1.02
10        0.45sec    111.11M         1.00
11        0.45sec    111.11M         1.00
12        0.48sec    104.17M         1.07
mean:     0.47sec    105.33M         1.05

Total absolute time: 6.18 sec

Abstraction Penalty: 1.05 was 1.12 without your patch applied.

-O2
test      absolute   additions      ratio with
number    time       per second     test0

 0        0.44sec    113.64M         1.00
 1        0.45sec    111.11M         1.02
 2        0.47sec    106.38M         1.07
 3        0.62sec    80.65M         1.41
 4        0.60sec    83.33M         1.36
 5        0.56sec    89.29M         1.27
 6        0.57sec    87.72M         1.30
 7        0.56sec    89.29M         1.27
 8        0.56sec    89.29M         1.27
 9        0.62sec    80.65M         1.41
10        0.60sec    83.33M         1.36
11        0.62sec    80.65M         1.41
12        0.60sec    83.33M         1.36
mean:     0.56sec    90.01M         1.26

Total absolute time: 7.27 sec

Abstraction Penalty: 1.26 was 1.30.

-O3
test      absolute   additions      ratio with
number    time       per second     test0

 0        0.44sec    113.64M         1.00
 1        0.48sec    104.17M         1.09
 2        0.48sec    104.17M         1.09
 3        0.61sec    81.97M         1.39
 4        0.60sec    83.33M         1.36
 5        0.56sec    89.29M         1.27
 6        0.56sec    89.29M         1.27
 7        0.56sec    89.29M         1.27
 8        0.56sec    89.29M         1.27
 9        0.60sec    83.33M         1.36
10        0.61sec    81.97M         1.39
11        0.60sec    83.33M         1.36
12        0.60sec    83.33M         1.36
mean:     0.56sec    89.99M         1.26

Total absolute time: 7.26 sec

Abstraction Penalty: 1.26 was 1.28.