[PATCH] teach emit_store_flag to use clz/ctz

[Andrew Pinski]

On Sat, May 5, 2012 at 11:52 PM, Maciej W. Rozycki <macro@linux-mips.org> wrote:
>  For the record: MIPS processors that implement CLZ/CLO (for some reason
> CTZ/CTO haven't been added to the architecture, but these operations can
> be cheaply transformed into CLZ/CLO) generally have a dedicated unit that
> causes no pipeline stall for these instructions even in the simplest
> pipeline designs like the M4K -- IOW they are issued at the usual one
> instruction per pipeline clock rate.

Even on Octeon this is true.  Though Octeon has seq/sneq too so it
does not matter in the end.

Note I originally was the one who proposed this optimization for
PowerPC even before I saw what XLC did.  See PR 10588 (which I filed 9
years ago)  and it seems we are about to fix it soon.

Thanks,
Andrew Pinski