[Bug target/48941] [arm gcc] NEON: Stack pointer operations performed even tho stack is not accessed at all in function.

["ramana at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48941

--- Comment #9 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> 2012-01-27 16:20:07 UTC ---
(In reply to comment #8)
> Any chance of seeing the work on this restart ?
> 
> I found this bug while looking for something that would help (I raised bug
> 51980 for the same kind of issue, still seen on trunk), but the patch attached
> to this bug does not solve the issue for code that is rich with zip/uzp/trn
> intrinsics.

I took a look at this for sometime when I was reviewing the patch submitted on
trunk. The problem in this case appears to go away with -fno-split-wide-types
but that in general is not a good idea. IIRC when RichardS and I talked about
it we did talk about maybe getting lower-subreg to pay some attention to it. 

Neon intrinsics have been improving ( I'd like to think) over time but they are
still not perfect unfortunately. I don't have time to look at this in the near
term myself. 

> 
> This is a major limitation of arm-gcc with respect to performance-critical Neon
> code in my opinion.

As they say, patches are welcome :) 

Ramana