Hi! On Tue, Apr 21, 2020 at 04:53:53PM -0500, Aaron Sawdey via Gcc-patches wrote: > For future architecture with prefix instructions, always use plq/pstq > rather than lq/stq for atomic load of quadword. Then we never have to > do the doubleword swap on little endian. Before this fix, -mno-pcrel > would generate lq with the doubleword swap (which was ok) and -mpcrel > would generate plq, also with the doubleword swap, which was wrong.
> 2020-04-20 Aaron Sawdey <acsaw...@linux.ibm.com> > > PR target/94622 > * config/rs6000/sync.md (load_quadpti): Add attr "prefixed" > if TARGET_PREFIXED. > (store_quadpti): Ditto. > (atomic_load<mode>): Do not swap doublewords if TARGET_PREFIXED as > plq will be used and doesn't need it. > (atomic_store<mode>): Ditto, for pstq. > +;; Pattern load_quadpti will always use plq for atomic TImode if > +;; TARGET_PREFIXED. It has the correct doubleword ordering on either LE > +;; or BE, so we can just move the result into the output register and > +;; do not need to do the doubleword swap for LE. Also this avoids any > +;; confusion about whether the lq vs plq might be used based on whether > +;; op1 has PC-relative addressing. We could potentially allow BE to > +;; use lq because it doesn't have the doubleword ordering problem. Two spaces after dot (twice). Thanks for the nice comments :-) > - [(set_attr "type" "store")]) > + [(set_attr "type" "store") > + (set (attr "prefixed") (if_then_else (match_test "TARGET_PREFIXED") > + (const_string "yes") > + (const_string "no")))]) Every 8 leading spaces should be a tab (it's annoying to have a mixture of styles, and then later to have patches randomly change such things as well. Spaces everywhere (no tabs ever) works fine for me, but that is not what we use, not in GCC, and not in our port. We could change that in GCC 11 perhaps? Opinions?) The patch is okay for trunk modulo those nits. Thanks! Segher
