On Fri, 17 Oct 2014, Uros Bizjak wrote:
While looking correct, I am a bit nervous about avx512fintrin.h
changes, mainly because I have not much experience with these
patterns. I have adder Kirill to CC for possible comments.
He asked for this part of the patch, and tested it:
https://gcc.gnu.org/ml/gcc-patches/2014-07/msg01954.html
I don't have many comments on simple arithmetic, and changes look
"trivial". I'd say that simple arithmetic part is OK for branch.
Thanks. I am testing the updated patch tonight and I'll commit. I am
planning on making a branch: ^/branches/x86-intrinsics-ext if noone
complains about the name.
One last note: scalar builtins preserve highpart of target register.
IIRC, I have tried to convert _mm_frcz_s{s,d} to use scalars, but
resulted in a horrible code. Current approach uses
__builtin_ia32_movs{s,d} to generate optimal code, but I didn't test
if current gcc improved in this part.
Operations that act on only part of a vector do tend to go badly indeed. I
remember working on something related at some point (the goal was to
handle v[0]+=2):
https://gcc.gnu.org/ml/gcc-patches/2012-12/msg00824.html
I don't remember exactly why I gave up on this. It may be a different
issue from yours with frcz, but I kept the impression from then that
builtins were still the way to go for anything non-trivial.
--
Marc Glisse
