Re: Gcc 3.1 performance regressions with respect to 2.95.3

[Jan Hubicka <jh at suse dot cz>]

> 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?

I think it is the presence of dead code, like it were in 3.0 case.
The dataflow pass should kill it.  I will try to find time to benchmark
it this weekend, but I am somewhat overloaded right now.

Honza
> 
> 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.
> 
> 
>