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Re: Default compiler optimization level for building dev sources

From: Óscar Fuentes
Subject: Re: Default compiler optimization level for building dev sources
Date: Fri, 22 Apr 2016 17:00:38 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.92 (gnu/linux)

Eli Zaretskii <address@hidden> writes:

>> I'm using Emacs 25.0.92 on Windows and it seems remarkably slower than
>> the previous binary. This one was built with a plain config && make
>> while the previous one had CFLAGS set to -O3 and other extra
>> optimization flags.
> So you are saying that -O2 (that's the default) is significantly
> slower than -O3?

No, I'm saying that this binary feels quite slower than the previous

> That's strange, my experience is that -O3 is
> generally not faster than -O2 and sometimes slower.

No arguing here. The cause must be elsewhere. The previous binary was
one year old and the current one is from a few days old master but I
doubt that such performance deterioration was caused by the introduced
changes with nobody noticing until now.

I need to investigate further.

>> Maybe the build does not turn on optimizations when it detects that the
>> sources are on a repo. Sorry for asking here instead of checking it
>> myself but today I have no access to the sources nor the web.
> I don't think so.  The default is -O2, so if you want -O3, you need to
> request it by saying "CFLAGS='-O3' ./configure ...".
> Do you still have the source directory tree where you b uilt the
> previous binary?  If so, please tell what configure-time switches you
> used and which compiler switches do you see in src/Makefile.

I *think* that the build dir is still around, but I have no access to
that VM for now. I trust you on the default CFLAGS, but maybe
makepkg-mingw (this is the MSYS2 way of building packages) did something
on its own. I'll check the Makefile and re-launch the build with some
flag for showing the compile command instead of just `CC foo.c' (I guess
that `make VERBOSE=1' will do.)

Thank you.

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