[Bug libstdc++/15002] Linewise stream input is unusably slow (std::string slow)

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-04-20 16:44 -------
Paolo, your patch helped a lot (I looked a profile generated by Shark).
I noticed that most of the time now is spent in std::string::_M_mutate from std::string::_M_replace_aux, 
not doing much at all.
Some suggestions after looking into the source/asm:
The calculation for __src could be moved inside the if statements, removing a load and two adds.

On the same box as before after Paolo's patch, so a little more than a 2x speedup:
tin:~/src/gnu/gcctest/iotest/iotest>time ./streams
1.340u 0.100s 0:01.43 100.6%    0+0k 0+0io 202pf+0w
tin:~/src/gnu/gcctest/iotest/iotest>time ./streams2
0.430u 0.010s 0:00.44 100.0%    0+0k 0+0io 199pf+0w
tin:~/src/gnu/gcctest/iotest/iotest>time ./stdio
0.080u 0.060s 0:00.15 93.3%     0+0k 0+0io 80pf+0w

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15002