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[3/5] AArch64: Improve A64FX memset for remaining bytes

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Simplify handling of remaining bytes. Avoid lots of taken branches and complex
whilelo computations, instead unconditionally write vectors from the end.

Reviewed-by: Naohiro Tamura <naohirot@fujitsu.com>
This commit is contained in:
Wilco Dijkstra 2021-08-10 13:42:07 +01:00
parent 9bc2ed8f46
commit 186092c6ba
1 changed files with 13 additions and 33 deletions
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46
sysdeps/aarch64/multiarch/memset_a64fx.S
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@ -130,38 +130,19 @@ L(unroll8):
b 1b
L(last):
whilelo p0.b, xzr, rest
whilelo p1.b, vector_length, rest
b.last 1f
st1b z0.b, p0, [dst, #0, mul vl]
st1b z0.b, p1, [dst, #1, mul vl]
ret
1: lsl tmp1, vector_length, 1 // vector_length * 2
whilelo p2.b, tmp1, rest
incb tmp1
whilelo p3.b, tmp1, rest
b.last 1f
st1b z0.b, p0, [dst, #0, mul vl]
st1b z0.b, p1, [dst, #1, mul vl]
st1b z0.b, p2, [dst, #2, mul vl]
st1b z0.b, p3, [dst, #3, mul vl]
ret
1: lsl tmp1, vector_length, 2 // vector_length * 4
whilelo p4.b, tmp1, rest
incb tmp1
whilelo p5.b, tmp1, rest
incb tmp1
whilelo p6.b, tmp1, rest
incb tmp1
whilelo p7.b, tmp1, rest
st1b z0.b, p0, [dst, #0, mul vl]
st1b z0.b, p1, [dst, #1, mul vl]
st1b z0.b, p2, [dst, #2, mul vl]
st1b z0.b, p3, [dst, #3, mul vl]
st1b z0.b, p4, [dst, #4, mul vl]
st1b z0.b, p5, [dst, #5, mul vl]
st1b z0.b, p6, [dst, #6, mul vl]
st1b z0.b, p7, [dst, #7, mul vl]
cmp count, vector_length, lsl 1
b.ls 2f
add tmp2, vector_length, vector_length, lsl 2
cmp count, tmp2
b.ls 5f
st1b z0.b, p0, [dstend, -8, mul vl]
st1b z0.b, p0, [dstend, -7, mul vl]
st1b z0.b, p0, [dstend, -6, mul vl]
5: st1b z0.b, p0, [dstend, -5, mul vl]
st1b z0.b, p0, [dstend, -4, mul vl]
st1b z0.b, p0, [dstend, -3, mul vl]
2: st1b z0.b, p0, [dstend, -2, mul vl]
st1b z0.b, p0, [dstend, -1, mul vl]
ret
L(L1_prefetch): // if rest >= L1_SIZE
@ -199,7 +180,6 @@ L(L2):
subs count, count, CACHE_LINE_SIZE
b.hi 1b
add count, count, CACHE_LINE_SIZE
add dst, dst, CACHE_LINE_SIZE
b L(last)
END (MEMSET)