Richard Sandiford <richard.sandif...@arm.com> wrote:
Alex Coplan <alex.cop...@arm.com> writes:
Note that an obvious omission here is that this patch does not touch the
mult patterns such as *add_<optab><ALLX:mode>_mult_<GPI:mode>. I found
that I couldn't hit these patterns with C code since multiplications by
powers of two always get turned into shifts by earlier RTL passes. If
there's a way to reliably hit these patterns, then perhaps these should
be updated as well.
Hmm. Feels like we should either update them or delete them. E.g.:
*adds_<optab><mode>_multp2
*subs_<optab><mode>_multp2
FWIW add_extvdi_multp2 seems to fire for me, building libstdc++ (c++11
cow-wstring-inst) on my [very experimental] initial attempts at a Darwin
port.
(I see these failures too because the platform assembler is based off the
LLVM
backend which complains)
Iain
were added alongside the adds3.c and subs3.c tests that you're updating,
so if the tests don't/no longer need the multp2 patterns to pass,
there's a good chance that the patterns are redundant.
For reasons I never understood, the canonical representation is to use
(mult …) for powers of 2 inside a (mem …) but shifts outside of (mem …)s.
So perhaps the patterns were originally for address calculations that had
been moved outside of a (mem …) and not updated to shifts instead of mults.
AFAICT the full list of affected patterns is:
*adds_<optab><mode>_multp2
*subs_<optab><mode>_multp2
*add_<optab><ALLX:mode>_mult_<GPI:mode>
*add_uxt<mode>_multp2
*sub_uxt<mode>_multp2
Is that right? If so, I think we should consider a follow-on patch
to delete them.
Testing:
* New test which checks for the correct syntax in all updated
patterns (fails before and passes after the aarch64.md change).
* New test can be assembled by both GAS and llvm-mc following the
change.
* Bootstrapped and regtested on aarch64-none-linux-gnu.
OK for master?
OK as-is if paired with a follow-on patch to delete the patterns above
(preapproved if it passes testing). Also OK without a follow-on patch
if the fix is extended to the patterns above too (but the first option
is better :-)).
Thanks for taking the time to find a test for each pattern.
Richard
