Date: Mon, 16 Feb 2004 17:23:18 -0500 From: Alexander Kabaev <ak03@gte.com> To: "Juan Tumani" <jtumani55@hotmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: FreeBSD 5.2 v/s FreeBSD 4.9 MFLOPS performance (gcc3.3.3v/sgcc2.9.5) Message-ID: <20040216172318.4b76daa2@kanpc.gte.com> In-Reply-To: <BAY12-F541stYkcOj3i00018525@hotmail.com> References: <BAY12-F541stYkcOj3i00018525@hotmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, 16 Feb 2004 16:36:35 -0500 "Juan Tumani" <jtumani55@hotmail.com> wrote: > Thanks Matt for picking up on the linker problem. Patching the kernel > would, to me, be masking the real problem. > > What other "improvements" does gcc333 have over gcc295 that might > explain why it's linked products run in a half-fast mode (take twice+ > as long)? > > JT > > > >From: Matthew Dillon <dillon@apollo.backplane.com> > >To: "Juan Tumani" <jtumani55@hotmail.com> > >CC: des@des.no, freebsd-hackers@freebsd.org > >Subject: Re: FreeBSD 5.2 v/s FreeBSD 4.9 MFLOPS performance > >(gcc3.3.3v/sgcc2.9.5) > >Date: Mon, 16 Feb 2004 13:12:15 -0800 (PST) > > > > I'm surprised Bruce hasn't chimed in here yet. I guess he's > > tired of repeating himself. > > > > In 4.9, libcsu, which generates crt1.o (which is the start code > > for C programs which the linker links in automatically) has this > > line in > >it: > > > > andl $~0xf, %%esp # align stack to 16-byte > > boundary > > > > So anything linked with 4.9 is going to align the stack on a > > 16 byte boundary no matter WHAT the kernel does. > > > > FreeBSD-5 does not have this alignment in its crt1.o because > > GCC3 automatically aligns the stack on a per-procedure basis. > > Or at least it is supposed to. Maybe it's broke? :-) > > > > -Matt > > Quite possibly. I run the same test using the latest GCC snapshot configured as system compiler and did not see such a massive slowdown. GCC 3.3.3 wins slightly on most tests and loses only on module #2 of the flops.c program posted here. -- Alexander Kabaev
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20040216172318.4b76daa2>