On 1/24/25 3:57 AM, Robin Dapp wrote:
So this isn't a regression, but I can also understand the desire to fix
this fairly significant performance issue.
I'd argue it is a regression as the match.pd pattern that merges the permutes
was introduces after GCC 14.
Good point. I hadn't thought about it as resolving the performance
regression from that change.
After giving it a bit more thought, I'd still like to send the attached v2
because it excludes fewer cases and, consequently, requires fewer changes to
the test suite.
Regtested on rv64gcv_zvl512b.
Regards
Robin
[PATCH v2] RISC-V: Disable two-source permutes for now [PR117173].
After testing on the BPI (4.2% improvement for x264 input 1, 4.4% for
input 2) and the discussion in PR117173 I figured it's best to disable
the two-source permutes by default for now.
The patch adds a parameter "riscv-two-source-permutes" which restores
the old behavior.
PR target/117173
gcc/ChangeLog:
* config/riscv/riscv-v.cc (shuffle_generic_patterns): Only
support single-source permutes by default.
* config/riscv/riscv.opt: New param "riscv-two-source-permutes".
gcc/testsuite/ChangeLog:
* gcc.dg/fold-perm-2.c: Run with two-source permutes.
* gcc.dg/pr54346.c: Ditto.
OK
jeff
