------- Comment #9 from dave at hiauly1 dot hia dot nrc dot ca 2009-01-12 18:01 ------- Subject: Re: [4.4 Regression] Incorrect delayed branch optimization
> I've been building parts of glibc's vfprintf code with -fno-delayed-branch for > hppa because of bugs in DBR. I never filed a bug because it was almost > impossible for me to reduce the vfprintf code (large file, large tables, long > jumps). I would guess that this particular regression has something to do with the new register allocator. The general problem mentioned by Richard Sandiford dbr_schedule is the only user of resource.c, which is based on this horrible hack of assuming that, although the basic block information is no longer up-to-date, we can still rely on the live register sets before BARRIERs. We also assume that we can rely on REG_DEAD notes to some extent: if a register is marked dead by a REG_DEAD note, and isn't set again before the next label, we assume it really is dead at the label. is more serious. The delayed branch optimisation is run at all levels. So, the generated code may be wrong if a user doesn't specify -fno-delayed-branch. As this problem affects more than the PA, possibly the priority of this report should be increased. Dave -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38740
