[AArch64] Predicated SVE comparison folds

This patch adds SVE patterns that combine a PTRUE-predicated
comparison with a separate AND.  The main benefit is for
optimising ANDs with the loop predicate, as in the testcase.
However, one of the potential drawbacks is that it triggers
even for cases in which two naturally-parallel comparisons
are ANDed together.  Whether that's a win or a less will
depend on the schedule, but it has the potential to be a win
more often than a loss.

The combine patterns are undeniably ugly.  One way of getting
around them would be to allow 1->1 "splits" when combining
2 instructions, as well as 1->2 splits when combining more
than 2 instructions (although that wouldn't really be a split).
Another would be to have a way of defining target-specific
rtx simplifications.  branches/ARM/sve-branch has a prototype
implementation of that, but it would need some clean-up before being
ready to submit.  It would also be good to make it closer to the
match.pd style.

Until then, I think what the combine patterns are doing is the
"correct" implementation given the current infrastructure.

2018-05-08  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* config/aarch64/aarch64-sve.md (*pred_cmp<cmp_op><mode>_combine)
	(*pred_cmp<cmp_op><mode>, *fcm<cmp_op><mode>_and_combine)
	(*fcmuo<mode>_and_combine, *fcm<cmp_op><mode>_and)
	(*fcmuo<mode>_and): New patterns.

gcc/testsuite/
	* gcc.target/aarch64/sve/vcond_6.c: Do not expect any ANDs.
	XFAIL the BIC test.
	* gcc.target/aarch64/sve/vcond_7.c: New test.
	* gcc.target/aarch64/sve/vcond_7_run.c: Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r260031

0 files changed, 0 insertions, 0 deletions