https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106415
--- Comment #3 from Undefined Opcode <undefinedopcode2 at gmail dot com> --- Created attachment 53348 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53348&action=edit dump of buggy optimization pass (In reply to Andrew Pinski from comment #2) > I suspect this is a target cost model issue ... > > You can look at the ivopts dump to see the costs there. Funny, I was just about to reply to the thread about this. It looks like it's choosing candidate 7. I've also included the candidate 3 info for completeness. Candidate 3: Incr POS: orig biv IV struct: Type: short int Base: 15 Step: -1 Biv: N Overflowness wrto loop niter: No-overflow ... <trimmed> ... Candidate 7: Var befor: ivtmp.19 Var after: ivtmp.19 Incr POS: before exit test IV struct: Type: unsigned int Base: 15 Step: 4294967295 Biv: N Overflowness wrto loop niter: Overflow ... <trimmed> ... <Candidate Costs>: cand cost 0 5 1 5 2 5 3 4 4 5 5 5 6 5 7 5 8 5 It's odd to me that it's choosing 7 over 3, since 3 is clearly lower cost. It also spits out "group candidate costs", but I'm not sure what those actually represent (sorry, this is my first time poking through GCC optimization internals). I've attached a copy of test.c.174t.ivopts if someone else can make more sense of it.
