On Thu, 20 Dec 2012, Jakub Jelinek wrote: > On Thu, Dec 20, 2012 at 02:51:55PM +0100, Richard Biener wrote: > > In the PR we perform expression replacement of an FP operation > > across a builtin call that sets the FP control register. This > > patch restricts replacement across calls further, from allowing > > all builtins to only allowing those without side-effects. > > > > Allowing replacement over calls at all was to not pessimize > > FP code generation for example for sqrt which is most often > > expanded to a single instruction. > > > > Bootstrap and regtest running on x86_64-unknown-linux-gnu. > > > > Comments? > > Wouldn't it be better to have there a list of known builtins over which it > is fine to do TER? I'd bet most of memory or string builtins that don't > call malloc/free should be still ok, but they surely have side-effects.
I'm not sure - the original reason was that replacing across calls made us spill more because there was a call. We agreed that replacing across calls isn't usually a good idea but put in the (admittedly bad) workaround to still allow doing so across likely-not-calls. string builtins generally will expand to calls though. I was thinking of even making it stronger and increment "cur_call_cnt" when the stmt (even non-call) has side-effects (would for example cover volatile asms or general volatile touching insns). Richard. > > 2012-12-20 Richard Biener <rguent...@suse.de> > > > > PR middle-end/55752 > > * tree-ssa-ter.c (find_replaceable_in_bb): Only allow replacing > > across calls with no side-effects. > > Jakub > > -- Richard Biener <rguent...@suse.de> SUSE / SUSE Labs SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 GF: Jeff Hawn, Jennifer Guild, Felix Imend
