Date: Sun, 31 Oct 2004 16:41:00 +0100 (MET)
Message-Id: <200410311541.i9VFf0ah023857@harpo.it.uu.se>
From: Mikael Pettersson <mikpe@csd.uu.se>
To: linux-kernel@vger.kernel.org, pluto@pld-linux.org
Subject: Re: unit-at-a-time...
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1001
Lines: 24

On Sun, 31 Oct 2004 15:57:00 +0100, pluto@pld-linux.org wrote:
>/i386/Makefile:# Disable unit-at-a-time mode, it makes gcc use a lot morestack
>/i386/Makefile:CFLAGS += $(call cc-option,-fno-unit-at-a-time)
>
>/x86_64/Makefile:# -funit-at-a-time shrinks the kernel .text considerably
>/x86_64/Makefile:CFLAGS += $(call cc-option,-funit-at-a-time)
>
>Which solution is correct?

Disabling unit-at-a-time for i386 is definitely correct.
I've personally observed horrible runtime corruption bugs
in early 2.6 kernels when they were compiled with gcc-3.4
without the -fno-unit-at-a-time fix.

x86-64 is a different architecture. It's possible its larger
number of registers reduces spills enough that gcc's failure
to merge stack slots doesn't matter.

/Mikael
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