On Sat, 23 Jun 2012, Jan Hubicka wrote: > > > > Tailcalls have no argument setup cost and no return value cost. > > This patch adjusts estminate_num_insns to reflect that. > > > > Honza, does this look correct? > > > > Bootstrapped and tested on x86_64-unknown-linux-gnu. > > > > Thanks, > > Richard. > > > > 2012-06-20 Richard Guenther <rguent...@suse.de> > > > > * tree-inline.c (estimate_num_insns): Estimate call cost for > > tailcalls properly. > > Well, as discussed offline, this change should currently be no-op since > we discover tail calls only very late in the game. > > I am not sure I agree that the argument costs are zeroed out. I.e. the > arguments are generally passed the same way as they would be for normal call, > just they are homed at different place of the stack frame. > (note that we mark by the tail call flag far more calls than those that > are really expanded to tailcall because target limitations are checked only > in calls.c). > > Finally ipa-cp use estimate_move cost to estimate savings for propagating > and I think there is risk in arriving to negative numbers when costs > are not accounted at all calls. > > So I am not sure we want to keep the patch in mainline in the current form...
I have reverted the patch. Richard.
