This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PowerPC] PR23774 stack backchain broken saga


Especially as the ABI states that the write of the backlink
and the stack pointer update _have_ to be done in one insn.

That's on allocation. Deallocation isn't so critical. You just need to
ensure the backchain is written before updating sp.

Yes, but your example generated code showed allocation with two insns. Of course it works, but it's not allowed by the ABI.

Hmm, on powerpc64-linux you could even alloc up to 288 bytes without
an atomic update, since 288 bytes below the current sp is available for
use.

Yes. Question is, can GCC support this (easily) -- it would have to keep track how much space it already alloca()'ed before doing _this_ alloca().


Segher



Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]