Re: [ACPI] ACPI mentioned on lwn.net/kernel

["Martin Eriksson" <nitrax@giron.wox.org>]

----- Original Message -----
From: "Jamie Lokier" <lk@tantalophile.demon.co.uk>
To: "Linus Torvalds" <torvalds@transmeta.com>
Cc: <linux-kernel@vger.kernel.org>
Sent: Saturday, January 26, 2002 4:41 AM
Subject: Re: [ACPI] ACPI mentioned on lwn.net/kernel


> Linus Torvalds wrote:
> > It's sad that gcc relegates "optimize for size" to a second-class
> > citizen.  Instead of having a "-Os" (that optimizes for size and doesn't
> > work together with other optimizations), it would be better to have a
> > "-Olargecode", which explicitly enables "don't care about code size" for
> > those (few) applications where it makes sense.
>
> Btw, there have been suggestions that -Os may actually be faster for x86
> code on current processors.

Hmm.. I tried to compile the kernel with -Os (gcc 2.96-98) and I just got a
~1% smaller vmlinux and a ~3% smaller bzImage. Maybe the size optimizations
doesn't show on these files? Internal data structures that are much bigger
than "real" code?

This is how I did:
--- Makefile    Sat Jan 26 17:15:52 2002
+++ Makefile.Os Sat Jan 26 17:15:30 2002
@@ -88,7 +88,7 @@

 CPPFLAGS := -D__KERNEL__ -I$(HPATH)

-CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes -Wno-trigraphs -O2 \
+CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes -Wno-trigraphs -Os \
          -fomit-frame-pointer -fno-strict-aliasing -fno-common
 AFLAGS := -D__ASSEMBLY__ $(CPPFLAGS)

 _____________________________________________________
|  Martin Eriksson <nitrax@giron.wox.org>
|  MSc CSE student, department of Computing Science
|  Umeå University, Sweden

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