Re: A workaround for PR 19038

[Jeffrey A Law <law at redhat dot com>]

On Wed, 2004-12-29 at 01:04 +0200, Mostafa Hagog wrote:
> 
> 
> 
> The attached patch implements loop header copying in the RTL level
> to work around the problem in http://gcc.gnu.org/PR19038
> I know that this patch is controversial, but it could be added
> at first at -O3 (or -O2) and disabled after the final fix in
> out-of-ssa. Anyhow, I thought it would be helpful to put the
> patch on the mailing list.
> Currently this patch buy us improvements of 3.5% on SPEC (a 66%
> for 176.gcc benchmark) on a G5 machine.  Compile time wasn't
> affected by this patch, following are the compile time results
> on a G5:
> 
> % time gcc -c -O3 generate-3.4.ii
> 53.140u 1.590s 0:54.70 100.0%   0+0k 0+12io 0pf+0w
> % time gcc -c -frtl-loop-hc -O3 generate-3.4.ii
> 53.140u 1.670s 0:54.82 99.9%    0+0k 0+11io 0pf+0w
> % time ./compile_i_files.sh gcc
> 150.220u 15.050s 2:45.46 99.8%  0+0k 0+124io 0pf+0w
> % time ./compile_i_files.sh gcc -frtl-loop-hc
> 150.340u 14.850s 2:45.53 99.7%  0+0k 0+115io 0pf+0w
> % time ./compile_i_files.sh gcc -O3
> 656.550u 33.980s 11:30.50 100.0%        0+0k 0+296io 0pf+0w
> % time ./compile_i_files.sh gcc -O3 -frtl-loop-hc
> 658.510u 35.090s 11:33.77 99.9% 0+0k 0+313io 0pf+0w
> 
> Mostafa.
> 
> 
> (See attached file: rtl_loop_ch.patch)
Is this still necessary/useful if the out-of-ssa doesn't create the
bogon basic block?  

jeff