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ARM: Improve armv7 memcpy performance.

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Only enter the aligned copy loop with buffers that can be 8-byte
aligned. This improves performance slightly on Cortex-A9 and
Cortex-A15 cores for large copies with buffers that are 4-byte
aligned but not 8-byte aligned.

ports/ChangeLog.arm:

2013-09-16  Will Newton  <will.newton@linaro.org>

	* sysdeps/arm/armv7/multiarch/memcpy_impl.S: Tighten check
	on entry to aligned copy loop to improve performance.
This commit is contained in:
Will Newton 2013-08-07 14:15:52 +01:00
parent f06dd27b0c
commit cd90698b54
2 changed files with 10 additions and 6 deletions
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5
ports/ChangeLog.arm
View File

@ -1,3 +1,8 @@
2013-09-16 Will Newton <will.newton@linaro.org>
* sysdeps/arm/armv7/multiarch/memcpy_impl.S: Tighten check
on entry to aligned copy loop to improve performance.
2013-08-30 Roland McGrath <roland@hack.frob.com>
* sysdeps/arm/armv6t2/strlen.S: Use sfi_pld and sfi_breg macros.

11
ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
View File

@ -24,7 +24,6 @@
ARMv6 (ARMv7-a if using Neon)
ARM state
Unaligned accesses
LDRD/STRD support unaligned word accesses
*/
@ -369,8 +368,8 @@ ENTRY(memcpy)
cfi_adjust_cfa_offset (FRAME_SIZE)
cfi_rel_offset (tmp2, 0)
cfi_remember_state
and tmp2, src, #3
and tmp1, dst, #3
and tmp2, src, #7
and tmp1, dst, #7
cmp tmp1, tmp2
bne .Lcpy_notaligned
@ -381,9 +380,9 @@ ENTRY(memcpy)
vmov.f32 s0, s0
#endif
/* SRC and DST have the same mutual 32-bit alignment, but we may
/* SRC and DST have the same mutual 64-bit alignment, but we may
still need to pre-copy some bytes to get to natural alignment.
We bring DST into full 64-bit alignment. */
We bring SRC and DST into full 64-bit alignment. */
lsls tmp2, dst, #29
beq 1f
rsbs tmp2, tmp2, #0
@ -515,7 +514,7 @@ ENTRY(memcpy)
.Ltail63aligned: /* Count in tmp2. */
/* Copy up to 7 d-words of data. Similar to Ltail63unaligned, but
we know that the src and dest are 32-bit aligned so we can use
we know that the src and dest are 64-bit aligned so we can use
LDRD/STRD to improve efficiency. */
/* TMP2 is now negative, but we don't care about that. The bottom
six bits still tell us how many bytes are left to copy. */