Re: GCC 3.0 Release Criteria

[Andrew Morton <andrewm at uow dot edu dot au>]

Mark Mitchell wrote:
> 
> As you know, we're beginning to prepare for the next major release of
> GCC.

Marvellous.

As far as I know, 2.7.2.3 is still the "official" compiler for the Linux
kernel.  I just did a quick comparison, building kernel 2.2.14 on a
2x500MHz/256MHz x86 (fast disks, no swapping, all caches hot):

2.7.2.3:

time make bzImage: 1 minute 46 seconds
size vmlinux
   text    data     bss     dec     hex filename
 866868   92300  106552 1065720  1042f8 vmlinux 

gcc version 2.96 20000221 (experimental)

time make bzImage: 2 minutes 50 seconds
size vmlinux
   text    data     bss     dec     hex filename
 948343   96872  107716 1152931  1197a3 vmlinux


Both compilers were built to the

	make CC="stage2/xgcc -Bstage2/" CFLAGS="-g -O2"

level prior to installation.

That's quite a difference in compilation time, bearing in mind that the
time spent in as, ld, ar and system is constant.

Thanks to Mr Moore, compilation time is probably less important than
cache footprint.  Could the 10% increase in code size be due to changed
alignment policy?


Dropping it from -O2 to -O1:

2.7.2.3:
	1min 39secs
	875346   92300  106552 1074198  106416 vmlinux 

2.96:
	2min 27secs
	966061   96872  107716 1170649  11dcd9 vmlinux
-- 
-akpm-