------- Comment #9 from ebotcazou at gcc dot gnu dot org 2006-10-30 16:01 ------- > Bug in biv selection, so strength reduction messes up: > > Loop from 45 to 46: 12 real insns. > Biv 60: insn 19 const (reg 59 [ pretmp.26 ]) > Biv 60: insn 22 const (1) > Biv 60: verified > Biv 60: initialized at insn 13: initial value (0) > > 60 is not a Biv:
Yeah, the limitations of loop.c are blatantly exposed by the new dialect generated by the RTL expanders in 4.x because of the 100 tree-opt passes. It turns out that 3.x finds the same BIVs: Biv 61: insn 22 const (1) Biv 61: insn 28 const (reg 65) Biv 61: verified Biv 61: initialized at insn 12: initial value (0) but the non-constant increment comes after the constant one, which is enough to prevent the GIV from being eliminated... -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28970
