On Tue, Mar 7, 2017 at 9:52 AM, Linus Torvalds <torva...@linux-foundation.org> wrote: > On Tue, Mar 7, 2017 at 9:38 AM, Josh Poimboeuf <jpoim...@redhat.com> wrote: >> >> So I'm thinking we should have -maccumulate-outgoing-args always enabled >> on x86_32 just like we already do on x86_64. > > Ugh. I realize we have workarounds for bugs, but I think > -maccumulate-outgoing-args is nasty. It just generates worse code by > avoiding the much nicer push/pop sequences, afaik. > > On x86-64 it's not such a big deal, because we pass the first six > arguments in registers anyway, so the arguments on the stack is a > fairly unusual special case. > > But on x86-32, we only have three argument registers, so this > braindamage is potentially worse. > > I guess we already do this in most situations due to the gcc bugs, but > I do think it's sad that we would do it for our _own_ bugs too. >
Is it our bug or a gcc bug? I would have thought -fno-omit-frame-pointer meant that the call-frame-to-return-address offset should be constant and -fomit-frame-pointer meant "do whatever". Also, maybe I'm missing something, but does gcc's code even allow the function to return sensibly? It could do it by a nasty calculation involving backing out the old esp from edi, but that seems quite overcomplicated. --Andy
