On Jun 23, 2006, at 9:39 PM, Andrew MacLeod wrote:
On Fri, 2006-06-23 at 15:07 -0700, Ian Lance Taylor wrote:
You omitted the RTL loop optimizer passes, which still do quite a bit
of work despite the tree-ssa loop passes. Also if-conversion and
some
minor passes, though they are less relevant.
Which brings up a good discussion. I presume the rtl loop
optimizers see
things exposed by addressing modes which aren't seen in the higher
level
code. I wonder what the "big gains" are here... and if they are
detectable at expansion time...
The one rtl loop optimizer which has nothing to do with addressing
modes and
loops is the doloop optimizer which is most likely possible to do
expansion time
and is one of the few loop optimizer which lowers register pressure.
The reason
why it lowers register pressure is because it makes use of a special
register for
loops (at least on PowerPC).
Thanks,
Andrew Pinski
