FreeBSD 5.2 v/s FreeBSD 4.9 MFLOPS performance (gcc3.3.3v/sgcc2.9.5)

[Juan Tumani]

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 at apollo.backplane.com>
>To: "Juan Tumani" <jtumani55 at hotmail.com>
>CC: des at des.no, freebsd-hackers at 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
>

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