[patch][rfc] Enabling more optimizations with -ON

Mike Frysinger vapier@gentoo.org
Thu Nov 20 20:12:00 GMT 2014


On 20 Nov 2014 10:02, Rafael Espíndola wrote:
> On 19 November 2014 19:25, Cary Coutant wrote:
> > Sorry, Rafael, I'm not ignoring your proposal -- I'm just pondering
> > it. I'm not wild about the -O option in the first place, since it
> > implies that we can nicely arrange the various optimizations into some
> > order. Right now, we use it in exactly two places: -O1 with
> > --compress-debug-sections uses ZIP compression level 9 instead of 1,
> > and -O2 does tail optimization of the string tables. Both of those
> > probably would have been cleaner with distinct options, but it was
> > convenient and both simply trade a little link time for a smaller
> > executable without any risk. It's not clear to me that --gc-sections
> > or --icf are universally applicable, which is what bundling them with
> > some optimization level would imply.
> 
> The issue then is that every software package has to test what liker
> is being used to link it.

unless you're going to hard require the GNU binutils package, then you already 
have this problem.

> In the compiler land a project can just use -ON (module bugs) instead
> of "-fopt1 -fopt2
> -fopt-something-introduced-in-gcc-4.9-but-an-error-in-4.8".

there are a huge number of options which never get turned on by any -ON flag. 
so if there's some feature you want that isn't in the existing bucket, you need 
to test for it yourself.
-mike
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