ddb1b4b4a4
here is the bugfix: - x86_64: Optimize ffsll function code size - S390: Fix building with disable mutli arch (BZ 31196) - sparc: Fix broken memset for sparc32 (BZ 31068) - sparc: Remove unwind information from signal return - sparc: Fix sparc64 memmove length comparison (BZ 31266) - sparc: Remove unwind information from signal return stubs (BZ 31244)
51 lines
1.7 KiB
Diff
51 lines
1.7 KiB
Diff
From 30e546d76e756fe4d2d20a8b2286de4fbf30ceb5 Mon Sep 17 00:00:00 2001
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From: Sunil K Pandey <skpgkp2@gmail.com>
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Date: Wed, 26 Jul 2023 08:34:05 -0700
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Subject: [PATCH 1/6] x86_64: Optimize ffsll function code size.
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Ffsll function randomly regress by ~20%, depending on how code gets
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aligned in memory. Ffsll function code size is 17 bytes. Since default
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function alignment is 16 bytes, it can load on 16, 32, 48 or 64 bytes
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aligned memory. When ffsll function load at 16, 32 or 64 bytes aligned
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memory, entire code fits in single 64 bytes cache line. When ffsll
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function load at 48 bytes aligned memory, it splits in two cache line,
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hence random regression.
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Ffsll function size reduction from 17 bytes to 12 bytes ensures that it
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will always fit in single 64 bytes cache line.
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This patch fixes ffsll function random performance regression.
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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(cherry picked from commit 9d94997b5f9445afd4f2bccc5fa60ff7c4361ec1)
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---
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sysdeps/x86_64/ffsll.c | 10 +++++-----
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1 file changed, 5 insertions(+), 5 deletions(-)
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diff --git a/sysdeps/x86_64/ffsll.c b/sysdeps/x86_64/ffsll.c
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index a1c13d4906..0c6680735c 100644
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--- a/sysdeps/x86_64/ffsll.c
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+++ b/sysdeps/x86_64/ffsll.c
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@@ -26,13 +26,13 @@ int
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ffsll (long long int x)
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{
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long long int cnt;
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- long long int tmp;
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- asm ("bsfq %2,%0\n" /* Count low bits in X and store in %1. */
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- "cmoveq %1,%0\n" /* If number was zero, use -1 as result. */
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- : "=&r" (cnt), "=r" (tmp) : "rm" (x), "1" (-1));
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+ asm ("mov $-1,%k0\n" /* Initialize cnt to -1. */
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+ "bsf %1,%0\n" /* Count low bits in x and store in cnt. */
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+ "inc %k0\n" /* Increment cnt by 1. */
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+ : "=&r" (cnt) : "r" (x));
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- return cnt + 1;
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+ return cnt;
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}
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#ifndef __ILP32__
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--
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2.33.0
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