Re: -O2 vs -O3

From: Horst von Brand (vonbrand@sleipnir.valparaiso.cl)
Date: Sat May 27 2000 - 13:13:32 EST


Christopher Thompson <chris@hypocrite.org> said:
> Here are some stats just from compiling the kernel. Please note that I did
> *not* try booting any of these kernels so they might not actually work:
>
> quoted time is user time on an unloaded system, compiling 2.3.99-pre8
>
> -O0: fails compile
> -O1: 7 min 22 s --> 807594 bytes

Shouldn't work. Fuction inlining is only done with -O2 and above (strange
it linked at all). Most probably modules will fail for want of inb(),
outb() et al.

> -O2: 8 min 38 s --> 830397 bytes
> -O3: 8 min 55 s --> 869151 bytes

Cost of overinlining and overzealous loop replication...

> -Os: 8 min 36 s --> 819874 bytes

No inlining at all, will probably kill several places that expect inlining.

--
Horst von Brand                             vonbrand@sleipnir.valparaiso.cl
Casilla 9G, Viņa del Mar, Chile                               +56 32 672616

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