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 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
