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[AArch64] Adjust writeback in non-zero memset

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This fixes an ineffiency in the non-zero memset.  Delaying the writeback
until the end of the loop is slightly faster on some cores - this shows
~5% performance gain on Cortex-A53 when doing large non-zero memsets.

	* sysdeps/aarch64/memset.S (MEMSET): Improve non-zero memset loop.
This commit is contained in:
Wilco Dijkstra 2018-11-20 12:37:00 +00:00
parent 9a62a9397d
commit 5770c0ad1e
2 changed files with 8 additions and 3 deletions
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4
ChangeLog
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@ -1,3 +1,7 @@
2018-11-20 Wilco Dijkstra <wdijkstr@arm.com>
* sysdeps/aarch64/memset.S (MEMSET): Improve non-zero memset loop.
2018-11-20 Joseph Myers <joseph@codesourcery.com>
* conform/conformtest.py (ElementTest.run): Use unique identifiers

7
sysdeps/aarch64/memset.S
View File

@ -89,10 +89,10 @@ L(set_long):
b.eq L(try_zva)
L(no_zva):
sub count, dstend, dst /* Count is 16 too large. */
add dst, dst, 16
sub dst, dst, 16 /* Dst is biased by -32. */
sub count, count, 64 + 16 /* Adjust count and bias for loop. */
1: stp q0, q0, [dst], 64
stp q0, q0, [dst, -32]
1: stp q0, q0, [dst, 32]
stp q0, q0, [dst, 64]!
L(tail64):
subs count, count, 64
b.hi 1b
@ -183,6 +183,7 @@ L(zva_other):
subs count, count, zva_len
b.hs 3b
4: add count, count, zva_len
sub dst, dst, 32 /* Bias dst for tail loop. */
b L(tail64)
#endif