>>> On 24.10.14 at 11:52, <richard.guent...@gmail.com> wrote: > On Fri, Oct 24, 2014 at 11:18 AM, Jakub Jelinek <ja...@redhat.com> wrote: >> On Fri, Oct 24, 2014 at 11:10:08AM +0200, Richard Biener wrote: >>> >> For something in static storage, this seems OK. However, I think a hard >>> >> register variable ought to be left alone -- even if we can't spill it to >>> >> a stack slot today, there's a reasonable chance we might add that >>> >> capability in the future. >>> > >>> > Hmm, but then wouldn't it need to be the code generating the spill >>> > that's responsible for enforcing suitable alignment? I can certainly >>> > re-submit without the hard register special cased (as it would still >>> > fix the original issue I'm seeing), but it feels wrong to do so. >>> >>> Yes, ISTR the spilling code is supposed to update the required >>> stack alignment. After all the RA decision might affect required >>> alignment of spills. >> >> From what I remember, at RA time you already have to know conservatively >> that you'll want to do dynamic stack realignment and what the highest needed >> alignment will be, so various parts of expansion etc. conservatively compute >> what will be needed. I think that is because you e.g. need to reserve some >> registers (vDRAP, etc.) if doing dynamic realignment. >> If you conservatively assume you'll need dynamic stack realignment and after >> RA you find you really don't need it, there are some optimizations in >> prologue threading where it attempts to at least decrease amount of >> unnecessary code, but the harm has already been done. >> >> Might be that with LRA perhaps this could be changed and not conservatively >> assume more alignment than proven to be needed, but such code isn't there I >> think. > > I stand corrected then.
So am I to conclude then that I need to take out the hard register check in order for this to be accepted? Jan
