Date: Thu, 6 Dec 2007 08:34:08 -0800 From: "David O'Brien" <obrien@freebsd.org> To: Alexander Leidinger <Alexander@Leidinger.net> Cc: Boris Samorodov <bsam@ipt.ru>, Jan Lentfer <Jan.Lentfer@web.de>, freebsd-current@freebsd.org Subject: Re: Problems Building 7.0-Beta3 with -Os Message-ID: <20071206163408.GA37676@dragon.NUXI.org> In-Reply-To: <20071206084342.cv8xbmqg4k0co8kg@webmail.leidinger.net> References: <4756BAD3.4060905@web.de> <95938867@bb.ipt.ru> <20071205231628.GA15765@dragon.NUXI.org> <20071206072239.GA81748@team.vega.ru> <20071206084342.cv8xbmqg4k0co8kg@webmail.leidinger.net>
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Ruslan Ermilov <ru@freebsd.org> (from Thu, 6 Dec 2007 10:22:39 wrote:
>> In otherwords: -O1 < -Os < -O2 (properly)
>>
> I read it differently. From the manpage:
> : -Os Optimize for size. -Os enables all -O2 optimizations that do not
> : typically increase code size. It also performs further optimiza-
> : tions designed to reduce code size.
>
> It says that -Os is a subset of -O2 optimizations plus some
> extra optimizations. Reading further in a manpage, there's
> only one, -mspace.
Yeah, GCC 4.2 now adds a few things to -Os:
sets optimize = 2, and
remove from -O1: flag_tree_ch
remove from -O2: flag_tree_pre
}
if (optimize_size)¶ {¶
align_loops = 1;
align_jumps = 1;
align_labels = 1;¶
align_functions = 1;¶
flag_reorder_blocks = 0;¶
flag_reorder_blocks_and_partition = 0;¶
/* Inlining of very small functions usually reduces total size. */¶
set_param_value ("max-inline-insns-single", 5);¶
set_param_value ("max-inline-insns-auto", 5);¶
flag_inline_functions = 1; // taken from -O3¶
/* We want to crossjump as much as possible. */¶
set_param_value ("min-crossjump-insns", 1);
}
On Thu, Dec 06, 2007 at 08:43:42AM +0100, Alexander Leidinger wrote:
> And after the import of the new gcc in 7, a lot of people noticed, that
> the resulting binaries are larger with -Os than with -O2.
quynh:/usr/src/usr.bin/vi> uname -m
amd64
quynh:/usr/src/usr.bin/vi> /bin/ls -l nvi.-O*
-rwxr-xr-x 1 root ncvs 366894 Dec 6 08:21 nvi.-O2
-rwxr-xr-x 1 root ncvs 313043 Dec 6 08:21 nvi.-Os
quynh:/usr/src/usr.bin/vi> size nvi.-O*
text data bss dec hex filename
326132 1944 4392 332468 512b4 nvi.-O2
273759 1944 4392 280095 4461f nvi.-Os
Perhaps you mean *sometimes* larger.
Also -Os goal is run-time foot print, not disk foot print.
--
-- David (obrien@FreeBSD.org)
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