Re: [PATCH] mm/pg-r4k.c: Dump the generated code

[Thiemo Seufer <ths@networkno.de>]

Franck Bui-Huu wrote:
> Maciej W. Rozycki wrote:
> > On Tue, 9 Oct 2007, Franck Bui-Huu wrote:
> > 
> >>>  What would be the gain for the kernel from using "-march=4ksd" rather 
> >>> than "-march=mips32r2"?
> >>>
> >> It actually results in a kernel image ~30kbytes smaller for the former
> >> case. It has been discussed sometimes ago on this list. I'm sorry but
> >> I don't know why...
> > 
> >  Perhaps the pipeline description for the 4KSd CPU is different from the 
> > default for the MIPS32r2 ISA.  Barring a study of GCC sources, if that 
> > really troubles you, you could build the same version of the kernel with 
> > these options:
> > 
> > 1. "-march=mips32r2"
> > 
> > 2. "-march=4ksd"
> > 
> > 3. "-march=mips32r2 -mtune=4ksd"
> > 
> > and compare the results.  I expect the results of #2 and #3 to be the same 
> > and it would just back up my suggestion about keeping CPU-specific 
> > optimisations separate from the CPU selection.
> 
> I think you misunderstood me, my own fault: the kernel was smaller
> with "-march=4ksd". It was bigger when using "-march=mips32r2 -smartmips".

Could you check what "-march=mips32r2 -smartmips -mtune=4ksd" does?
I expect it to have the same result than "-march=4ksd".


Thiemo