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| author | Naohiro Tamura via Libc-alpha <libc-alpha@sourceware.org> | 2021-08-27 05:03:04 +0000 |
|---|---|---|
| committer | Szabolcs Nagy <szabolcs.nagy@arm.com> | 2021-09-03 15:59:46 +0100 |
| commit | 23777232c23f80809613bdfa329f63aadf992922 (patch) | |
| tree | 02c8d663d92010187a3176126b7dfb6247540f81 | |
| parent | 69623c0db0a540f26ee537bae09446d3dcdf1f80 (diff) | |
| download | glibc-23777232c23f80809613bdfa329f63aadf992922.tar.gz glibc-23777232c23f80809613bdfa329f63aadf992922.tar.xz glibc-23777232c23f80809613bdfa329f63aadf992922.zip | |
AArch64: Update A64FX memset not to degrade at 16KB
This patch updates unroll8 code so as not to degrade at the peak performance 16KB for both FX1000 and FX700. Inserted 2 instructions at the beginning of the unroll8 loop, cmp and branch, are a workaround that is found heuristically. Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
| -rw-r--r-- | sysdeps/aarch64/multiarch/memset_a64fx.S | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/sysdeps/aarch64/multiarch/memset_a64fx.S b/sysdeps/aarch64/multiarch/memset_a64fx.S index 7bf759b6a7..f7dfdaace7 100644 --- a/sysdeps/aarch64/multiarch/memset_a64fx.S +++ b/sysdeps/aarch64/multiarch/memset_a64fx.S @@ -96,7 +96,14 @@ L(vl_agnostic): // VL Agnostic L(unroll8): sub count, count, tmp1 .p2align 4 -1: st1b_unroll 0, 7 + // The 2 instructions at the beginning of the following loop, + // cmp and branch, are a workaround so as not to degrade at + // the peak performance 16KB. + // It is found heuristically and the branch condition, b.ne, + // is chosen intentionally never to jump. +1: cmp xzr, xzr + b.ne 1b + st1b_unroll 0, 7 add dst, dst, tmp1 subs count, count, tmp1 b.hi 1b |