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Precompiled headers - still useful feature?
- From: Martin LiÅka <mliska at suse dot cz>
- To: GCC Development <gcc at gcc dot gnu dot org>
- Date: Wed, 27 May 2015 10:14:06 +0200
- Subject: Precompiled headers - still useful feature?
- Authentication-results: sourceware.org; auth=none
Hello.
I would like to ask folks what is their opinion about support of precompiled headers for
future releases of GCC. From my point of view, the feature brings some speed-up, but question
is if it's worth for?
Last time I hit precompiled headers was when I was rewriting memory
allocation statistics infrastructure, where GGC memory is 'streamed' and loaded afterwards
in usage of precompiled headers.
Because of that I was unable to track some pointers that were allocated in the first phase
of compilation.
There are numbers related to --disable-libstdcxx-pch option:
Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz:
Boostrap time w/ precompiled headers enabled: 35m47s (100.00%)
Boostrap time w/ precompiled headers disabled: 36m27s (101.86%)
make -j9 check-target-libstdc++-v3 -k time:
precompiled headers enabled: 8m11s (100.00%)
precompiled headers disabled: 8m42s (106.31%)
Intel(R) Core(TM) i5-3320M CPU @ 2.60GHz:
Boostrap time w/ precompiled headers enabled: 57m35s (100.00%)
Boostrap time w/ precompiled headers disabled: 57m12s (99.33%)
Feel free to send any statistics, opinions and ideas.
Thank you,
Martin