Re: [patch 02/2] allow gcc4 to optimize unit-at-a-time

[Matt Mackall <mpm@selenic.com>]

On Wed, Dec 28, 2005 at 04:30:49PM +0100, Andi Kleen wrote:
> Ingo Molnar <mingo@elte.hu> writes:
> 
> > allow gcc4 compilers to optimize unit-at-a-time - which results in gcc
> > having a wider scope when optimizing. This also results in smaller code
> > when optimizing for size. (gcc4 does not have the stack footprint
> > problem of gcc3 compilers.)
> 
> I never had any trouble with stack footprint even with gcc 3.3 on x86-64
> and unit-at-a-time and it was always enabled. 

The particular offenders I remember were in lib/inflate.c running over
4K well before 4K stacks were in mainline, so I fixed it well before
anyone else got to see it.
 
> But one caveat: turning on unit-at-a-time makes objdump -S / make
> foo/bar.lst with CONFIG_DEBUG_INFO essentially useless because objdump
> cannot deal with functions being out of order in the object file. This
> can be a big problem while analyzing oopses - essentially you have
> to analyze the functions without source level information. And with
> unit-at-a-time they become bigger so it's more difficult.

Yeah, and it also makes stuff like bloat-o-meter output go all to hell.
 
> But I still think it's a good idea.

Indeed.

-- 
Mathematics is the supreme nostalgia of our time.