Hi all, Resurrecting this thread... > On 01/07/13 12:05, Kyrylo Tkachov wrote: > > Hi Richard, > > > >>> This hurts code size. > >>> Therefore I've disabled the new peephole2 for > optimize_insn_for_size_p > >> so that > >>> the original peephole before r200197 is used when optimising for > size. > >>> > >>> I've also added a test to confirm that the new peephole2 for the non- > CC > >>> setting variants is being used when optimising for speed, since the > >> large code > >>> should be more efficient because the scheduler won't have to deal > with > >>> condition-code setting. > >>> > >>> Ok for trunk? > >>> > >>> Thanks, > >>> Kyrill > >>> > >>> gcc/ > >>> 2013-06-21 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > >>> > >>> * config/arm/arm.md (peepholes for eq (reg1) (reg2/imm)): > >>> Use the flag setting variants when optimising for size. > >>> > >>> > >>> gcc/testsuite/ > >>> 2013-06-21 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > >>> > >>> * gcc.target/arm/pr46975-2.c: New test. > >>> > >> > >> Not ok. > >> > >> This re-introduces the bug that Meador was trying to fix. > >> > >> You need to ensure that the condition code register is dead before > >> applying this peephole. > > > > Thanks for the review. > > > > How about this? I'm reusing Meadors' peephole2 and guard the > application by > > checking the CC reg for deadness with peep2_regno_dead_p. > > > > Kyrill > > > > gcc/ > > 2013-07-01 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > > Meador Inge <mead...@codesourcery.com> > > > > * config/arm/arm.md (peepholes for eq (reg1) (reg2/imm)): > > Use the flag setting variants when optimising for size. > > > > > > gcc/testsuite/ > > 2013-07-01 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > > Meador Inge <mead...@codesourcery.com> > > > > * gcc.target/arm/pr46975-2.c: New test. > > > > +;; Rd = (eq (reg1) (reg2/imm)) // optimize for size on Thumb2 > +;; subs T1, Reg1, reg2 > +;; negs Rd, T1 > +;; adcs Rd, Rd, T1 > > Only the second operation has to be flag setting. A later pass will > convert the first and third instructions to flag clobbering if that's > the right thing to do on the target (which it currently always is, but > may not always remain so).
So I tried removing the flag setting from the peephole for the sub and adc instructions, and nothing ends up converting them to flag-setting instructions and we end up with: sub negs adc which is suboptimal for size. Is combine supposed to do decide whether to use flag-setting variants? Thanks, Kyrill
