cvs commit: src/sys/kern kern_sig.c

[Scott Long]

David O'Brien wrote:
> On Thu, Mar 03, 2005 at 07:06:24AM -0700, Scott Long wrote:
> 
>>a bit.  Also, there is talk about increasing the default kstack size due
>>to all of the extra inlining that the compiler does with the -O2 option
> 
> 
> I'd love more details on the extra inlining people are seeing with -O2.
> (i.e. specifics)  -O2 is not supose to do extra function inlining.  That
> is suppose to be a -O3 thing.
> 
> From the GCC manual:
> 
> -O3 Optimize yet more.
>     -O3 turns on all optimizations specified by -O2 and also turns on the
>     -finline-functions, -fweb and -frename-registers options.
> 
> -O2 Optimize even more.
>     GCC performs nearly all supported optimizations that do not involve a
>     space-speed tradeoff. The compiler does not perform loop unrolling or
>     function inlining when you specify -O2. As compared to -O, this
>     option increases both compilation time and the performance of the
>     generated code.
>     ..snip..
> 
> The -O2 options that affect size are:
>     -falign-functions  -falign-jumps  -falign-loops -falign-labels
>     -freorder-blocks -fprefetch-loop-arrays

Talk to Bill Paul about the massive amount of inlining that is happening
in the ieee80211 ioctl code, and the no_inline directives he had to use
to kludge around it.

Scott