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From: Wilco Dijkstra <wilco@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc] AArch64: Optimize memrchr Date: Tue, 17 Jan 2023 16:35:41 +0000 (GMT) [thread overview] Message-ID: <20230117163541.460763858C2B@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=00776241776e67fc666b896c1e85770f4f3ec1e1 commit 00776241776e67fc666b896c1e85770f4f3ec1e1 Author: Wilco Dijkstra <wilco.dijkstra@arm.com> Date: Wed Jan 11 13:51:17 2023 +0000 AArch64: Optimize memrchr Optimize the main loop - large strings are 43% faster on modern CPUs. Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Diff: --- sysdeps/aarch64/memrchr.S | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/sysdeps/aarch64/memrchr.S b/sysdeps/aarch64/memrchr.S index 9d2d29a396..621fc65109 100644 --- a/sysdeps/aarch64/memrchr.S +++ b/sysdeps/aarch64/memrchr.S @@ -26,7 +26,6 @@ * MTE compatible. */ -/* Arguments and results. */ #define srcin x0 #define chrin w1 #define cntin x2 @@ -77,31 +76,34 @@ ENTRY (__memrchr) csel result, result, xzr, hi ret + nop L(start_loop): - sub tmp, end, src - subs cntrem, cntin, tmp + subs cntrem, src, srcin b.ls L(nomatch) /* Make sure that it won't overread by a 16-byte chunk */ - add tmp, cntrem, 15 - tbnz tmp, 4, L(loop32_2) + sub cntrem, cntrem, 1 + tbz cntrem, 4, L(loop32_2) + add src, src, 16 - .p2align 4 + .p2align 5 L(loop32): - ldr qdata, [src, -16]! + ldr qdata, [src, -32]! cmeq vhas_chr.16b, vdata.16b, vrepchr.16b umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */ fmov synd, dend cbnz synd, L(end) L(loop32_2): - ldr qdata, [src, -16]! + ldr qdata, [src, -16] subs cntrem, cntrem, 32 cmeq vhas_chr.16b, vdata.16b, vrepchr.16b - b.ls L(end) + b.lo L(end_2) umaxp vend.16b, vhas_chr.16b, vhas_chr.16b /* 128->64 */ fmov synd, dend cbz synd, L(loop32) +L(end_2): + sub src, src, 16 L(end): shrn vend.8b, vhas_chr.8h, 4 /* 128->64 */ fmov synd, dend
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