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authorzhichang.yuan <zhichang.yuan@linaro.org>2014-04-28 06:11:31 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2014-05-23 15:07:48 +0100
commitb29a51fe0e0be63157d8661666be8bbfd8f0c5d7 (patch)
tree52fe220fdbab3501d732912e1d828e8cae6dbdd8 /arch
parent280adc1951c0c9fc8f2d85571ff563a1c412b1cd (diff)
downloadlinux-linaro-stable-b29a51fe0e0be63157d8661666be8bbfd8f0c5d7.tar.gz
arm64: lib: Implement optimized memset routine
This patch, based on Linaro's Cortex Strings library, improves the performance of the assembly optimized memset() function. Signed-off-by: Zhichang Yuan <zhichang.yuan@linaro.org> Signed-off-by: Deepak Saxena <dsaxena@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/lib/memset.S207
1 files changed, 185 insertions, 22 deletions
diff --git a/arch/arm64/lib/memset.S b/arch/arm64/lib/memset.S
index 87e4a68fbbbc..7c72dfd36b63 100644
--- a/arch/arm64/lib/memset.S
+++ b/arch/arm64/lib/memset.S
@@ -1,5 +1,13 @@
/*
* Copyright (C) 2013 ARM Ltd.
+ * Copyright (C) 2013 Linaro.
+ *
+ * This code is based on glibc cortex strings work originally authored by Linaro
+ * and re-licensed under GPLv2 for the Linux kernel. The original code can
+ * be found @
+ *
+ * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
+ * files/head:/src/aarch64/
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
@@ -16,6 +24,7 @@
#include <linux/linkage.h>
#include <asm/assembler.h>
+#include <asm/cache.h>
/*
* Fill in the buffer with character c (alignment handled by the hardware)
@@ -27,27 +36,181 @@
* Returns:
* x0 - buf
*/
+
+dstin .req x0
+val .req w1
+count .req x2
+tmp1 .req x3
+tmp1w .req w3
+tmp2 .req x4
+tmp2w .req w4
+zva_len_x .req x5
+zva_len .req w5
+zva_bits_x .req x6
+
+A_l .req x7
+A_lw .req w7
+dst .req x8
+tmp3w .req w9
+tmp3 .req x9
+
ENTRY(memset)
- mov x4, x0
- and w1, w1, #0xff
- orr w1, w1, w1, lsl #8
- orr w1, w1, w1, lsl #16
- orr x1, x1, x1, lsl #32
- subs x2, x2, #8
- b.mi 2f
-1: str x1, [x4], #8
- subs x2, x2, #8
- b.pl 1b
-2: adds x2, x2, #4
- b.mi 3f
- sub x2, x2, #4
- str w1, [x4], #4
-3: adds x2, x2, #2
- b.mi 4f
- sub x2, x2, #2
- strh w1, [x4], #2
-4: adds x2, x2, #1
- b.mi 5f
- strb w1, [x4]
-5: ret
+ mov dst, dstin /* Preserve return value. */
+ and A_lw, val, #255
+ orr A_lw, A_lw, A_lw, lsl #8
+ orr A_lw, A_lw, A_lw, lsl #16
+ orr A_l, A_l, A_l, lsl #32
+
+ cmp count, #15
+ b.hi .Lover16_proc
+ /*All store maybe are non-aligned..*/
+ tbz count, #3, 1f
+ str A_l, [dst], #8
+1:
+ tbz count, #2, 2f
+ str A_lw, [dst], #4
+2:
+ tbz count, #1, 3f
+ strh A_lw, [dst], #2
+3:
+ tbz count, #0, 4f
+ strb A_lw, [dst]
+4:
+ ret
+
+.Lover16_proc:
+ /*Whether the start address is aligned with 16.*/
+ neg tmp2, dst
+ ands tmp2, tmp2, #15
+ b.eq .Laligned
+/*
+* The count is not less than 16, we can use stp to store the start 16 bytes,
+* then adjust the dst aligned with 16.This process will make the current
+* memory address at alignment boundary.
+*/
+ stp A_l, A_l, [dst] /*non-aligned store..*/
+ /*make the dst aligned..*/
+ sub count, count, tmp2
+ add dst, dst, tmp2
+
+.Laligned:
+ cbz A_l, .Lzero_mem
+
+.Ltail_maybe_long:
+ cmp count, #64
+ b.ge .Lnot_short
+.Ltail63:
+ ands tmp1, count, #0x30
+ b.eq 3f
+ cmp tmp1w, #0x20
+ b.eq 1f
+ b.lt 2f
+ stp A_l, A_l, [dst], #16
+1:
+ stp A_l, A_l, [dst], #16
+2:
+ stp A_l, A_l, [dst], #16
+/*
+* The last store length is less than 16,use stp to write last 16 bytes.
+* It will lead some bytes written twice and the access is non-aligned.
+*/
+3:
+ ands count, count, #15
+ cbz count, 4f
+ add dst, dst, count
+ stp A_l, A_l, [dst, #-16] /* Repeat some/all of last store. */
+4:
+ ret
+
+ /*
+ * Critical loop. Start at a new cache line boundary. Assuming
+ * 64 bytes per line, this ensures the entire loop is in one line.
+ */
+ .p2align L1_CACHE_SHIFT
+.Lnot_short:
+ sub dst, dst, #16/* Pre-bias. */
+ sub count, count, #64
+1:
+ stp A_l, A_l, [dst, #16]
+ stp A_l, A_l, [dst, #32]
+ stp A_l, A_l, [dst, #48]
+ stp A_l, A_l, [dst, #64]!
+ subs count, count, #64
+ b.ge 1b
+ tst count, #0x3f
+ add dst, dst, #16
+ b.ne .Ltail63
+.Lexitfunc:
+ ret
+
+ /*
+ * For zeroing memory, check to see if we can use the ZVA feature to
+ * zero entire 'cache' lines.
+ */
+.Lzero_mem:
+ cmp count, #63
+ b.le .Ltail63
+ /*
+ * For zeroing small amounts of memory, it's not worth setting up
+ * the line-clear code.
+ */
+ cmp count, #128
+ b.lt .Lnot_short /*count is at least 128 bytes*/
+
+ mrs tmp1, dczid_el0
+ tbnz tmp1, #4, .Lnot_short
+ mov tmp3w, #4
+ and zva_len, tmp1w, #15 /* Safety: other bits reserved. */
+ lsl zva_len, tmp3w, zva_len
+
+ ands tmp3w, zva_len, #63
+ /*
+ * ensure the zva_len is not less than 64.
+ * It is not meaningful to use ZVA if the block size is less than 64.
+ */
+ b.ne .Lnot_short
+.Lzero_by_line:
+ /*
+ * Compute how far we need to go to become suitably aligned. We're
+ * already at quad-word alignment.
+ */
+ cmp count, zva_len_x
+ b.lt .Lnot_short /* Not enough to reach alignment. */
+ sub zva_bits_x, zva_len_x, #1
+ neg tmp2, dst
+ ands tmp2, tmp2, zva_bits_x
+ b.eq 2f /* Already aligned. */
+ /* Not aligned, check that there's enough to copy after alignment.*/
+ sub tmp1, count, tmp2
+ /*
+ * grantee the remain length to be ZVA is bigger than 64,
+ * avoid to make the 2f's process over mem range.*/
+ cmp tmp1, #64
+ ccmp tmp1, zva_len_x, #8, ge /* NZCV=0b1000 */
+ b.lt .Lnot_short
+ /*
+ * We know that there's at least 64 bytes to zero and that it's safe
+ * to overrun by 64 bytes.
+ */
+ mov count, tmp1
+1:
+ stp A_l, A_l, [dst]
+ stp A_l, A_l, [dst, #16]
+ stp A_l, A_l, [dst, #32]
+ subs tmp2, tmp2, #64
+ stp A_l, A_l, [dst, #48]
+ add dst, dst, #64
+ b.ge 1b
+ /* We've overrun a bit, so adjust dst downwards.*/
+ add dst, dst, tmp2
+2:
+ sub count, count, zva_len_x
+3:
+ dc zva, dst
+ add dst, dst, zva_len_x
+ subs count, count, zva_len_x
+ b.ge 3b
+ ands count, count, zva_bits_x
+ b.ne .Ltail_maybe_long
+ ret
ENDPROC(memset)