This is the mail archive of the
glibc-cvs@sourceware.org
mailing list for the glibc project.
GNU C Library master sources branch master updated. glibc-2.26.9000-970-g2bce01e
- From: siddhesh at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 13 Dec 2017 13:21:03 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.26.9000-970-g2bce01e
This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU C Library master sources".
The branch, master has been updated
via 2bce01ebbaf8db52ba4a5635eb5744f989cdbf69 (commit)
from 243b63337c2c02f30ec3a988ecc44bc0f6ffa0ad (commit)
Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.
- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=2bce01ebbaf8db52ba4a5635eb5744f989cdbf69
commit 2bce01ebbaf8db52ba4a5635eb5744f989cdbf69
Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Wed Dec 13 18:50:27 2017 +0530
aarch64: Improve strcmp unaligned performance
Replace the simple byte-wise compare in the misaligned case with a
dword compare with page boundary checks in place. For simplicity I've
chosen a 4K page boundary so that we don't have to query the actual
page size on the system.
This results in up to 3x improvement in performance in the unaligned
case on falkor and about 2.5x improvement on mustang as measured using
bench-strcmp.
* sysdeps/aarch64/strcmp.S (misaligned8): Compare dword at a
time whenever possible.
diff --git a/ChangeLog b/ChangeLog
index 22df17b..a5419e1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-12-13 Siddhesh Poyarekar <siddhesh@sourceware.org>
+
+ * sysdeps/aarch64/strcmp.S (misaligned8): Compare dword at a
+ time whenever possible.
+
2017-12-12 Carlos O'Donell <carlos@redhat.com>
* elf/Makefile [$(nss-crypt)$(static-nss-crypt) == yesno]
diff --git a/sysdeps/aarch64/strcmp.S b/sysdeps/aarch64/strcmp.S
index e99d662..c260e1d 100644
--- a/sysdeps/aarch64/strcmp.S
+++ b/sysdeps/aarch64/strcmp.S
@@ -72,6 +72,7 @@ L(start_realigned):
cbz syndrome, L(loop_aligned)
/* End of performance-critical section -- one 64B cache line. */
+L(end):
#ifndef __AARCH64EB__
rev syndrome, syndrome
rev data1, data1
@@ -145,12 +146,38 @@ L(mutual_align):
b L(start_realigned)
L(misaligned8):
- /* We can do better than this. */
+ /* Align SRC1 to 8 bytes and then compare 8 bytes at a time, always
+ checking to make sure that we don't access beyond page boundary in
+ SRC2. */
+ tst src1, #7
+ b.eq L(loop_misaligned)
+L(do_misaligned):
ldrb data1w, [src1], #1
ldrb data2w, [src2], #1
cmp data1w, #1
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
- b.eq L(misaligned8)
+ b.ne L(done)
+ tst src1, #7
+ b.ne L(misaligned8)
+
+L(loop_misaligned):
+ /* Test if we are within the last dword of the end of a 4K page. If
+ yes then jump back to the misaligned loop to copy a byte at a time. */
+ and tmp1, src2, #0xff8
+ eor tmp1, tmp1, #0xff8
+ cbz tmp1, L(do_misaligned)
+ ldr data1, [src1], #8
+ ldr data2, [src2], #8
+
+ sub tmp1, data1, zeroones
+ orr tmp2, data1, #REP8_7f
+ eor diff, data1, data2 /* Non-zero if differences found. */
+ bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
+ orr syndrome, diff, has_nul
+ cbz syndrome, L(loop_misaligned)
+ b L(end)
+
+L(done):
sub result, data1, data2
RET
END(strcmp)
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 5 +++++
sysdeps/aarch64/strcmp.S | 31 +++++++++++++++++++++++++++++--
2 files changed, 34 insertions(+), 2 deletions(-)
hooks/post-receive
--
GNU C Library master sources