https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89071
Uroš Bizjak <ubizjak at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2019-02-01
Assignee|unassigned at gcc dot gnu.org |ubizjak at gmail dot com
Ever confirmed|0 |1
--- Comment #14 from Uroš Bizjak <ubizjak at gmail dot com> ---
Created attachment 45582
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45582&action=edit
Additional patch to break partial SSE reg dependencies
Here is another patch that may help with partial SSE reg dependencies for
{R,}SQRTS{S,D}, RCPS{S,D} and ROUNDS{S,D} instructions. It takes the same
strategy as both ICC and clang take, that is:
a) load from mem with MOVS{S,D} and
b) in case of SSE, match input and output register.
The implementation uses preferred_for_speed attribute, so in cold sections or
when compiled with -Os, the compiler is still able to create direct load from
memory (SSE, AVX) and use unmatched registers for SSE targets.
So, the sqrt from memory is now compikled to:
movsd z(%rip), %xmm0
sqrtsd %xmm0, %xmm0
(SSE) or
vmovsd z(%rip), %xmm1
vsqrtsd %xmm1, %xmm1, %xmm0
(AVX).
And sqrt from unmatched input register will compile to:
sqrtsd %xmm1, %xmm1
movapd %xmm1, %xmm0
(SSE) or
vsqrtsd %xmm1, %xmm1, %xmm0
.
HJ, can you please benchmark this patch?
