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| /* SPDX-License-Identifier: GPL-2.0-only */
| /*
| * Copyright (C) 2013 ARM Ltd.
| * Copyright (C) 2013 Linaro.
| *
| * This code is based on glibc cortex strings work originally authored by Linaro
| * be found @
| *
| * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
| * files/head:/src/aarch64/
| */
|
| #include <linux/linkage.h>
| #include <asm/assembler.h>
|
| /*
| * compare memory areas(when two memory areas' offset are different,
| * alignment handled by the hardware)
| *
| * Parameters:
| * x0 - const memory area 1 pointer
| * x1 - const memory area 2 pointer
| * x2 - the maximal compare byte length
| * Returns:
| * x0 - a compare result, maybe less than, equal to, or greater than ZERO
| */
|
| /* Parameters and result. */
| src1 .req x0
| src2 .req x1
| limit .req x2
| result .req x0
|
| /* Internal variables. */
| data1 .req x3
| data1w .req w3
| data2 .req x4
| data2w .req w4
| has_nul .req x5
| diff .req x6
| endloop .req x7
| tmp1 .req x8
| tmp2 .req x9
| tmp3 .req x10
| pos .req x11
| limit_wd .req x12
| mask .req x13
|
| SYM_FUNC_START_WEAK_PI(memcmp)
| cbz limit, .Lret0
| eor tmp1, src1, src2
| tst tmp1, #7
| b.ne .Lmisaligned8
| ands tmp1, src1, #7
| b.ne .Lmutual_align
| sub limit_wd, limit, #1 /* limit != 0, so no underflow. */
| lsr limit_wd, limit_wd, #3 /* Convert to Dwords. */
| /*
| * The input source addresses are at alignment boundary.
| * Directly compare eight bytes each time.
| */
| .Lloop_aligned:
| ldr data1, [src1], #8
| ldr data2, [src2], #8
| .Lstart_realigned:
| subs limit_wd, limit_wd, #1
| eor diff, data1, data2 /* Non-zero if differences found. */
| csinv endloop, diff, xzr, cs /* Last Dword or differences. */
| cbz endloop, .Lloop_aligned
|
| /* Not reached the limit, must have found a diff. */
| tbz limit_wd, #63, .Lnot_limit
|
| /* Limit % 8 == 0 => the diff is in the last 8 bytes. */
| ands limit, limit, #7
| b.eq .Lnot_limit
| /*
| * The remained bytes less than 8. It is needed to extract valid data
| * from last eight bytes of the intended memory range.
| */
| lsl limit, limit, #3 /* bytes-> bits. */
| mov mask, #~0
| CPU_BE( lsr mask, mask, limit )
| CPU_LE( lsl mask, mask, limit )
| bic data1, data1, mask
| bic data2, data2, mask
|
| orr diff, diff, mask
| b .Lnot_limit
|
| .Lmutual_align:
| /*
| * Sources are mutually aligned, but are not currently at an
| * alignment boundary. Round down the addresses and then mask off
| * the bytes that precede the start point.
| */
| bic src1, src1, #7
| bic src2, src2, #7
| ldr data1, [src1], #8
| ldr data2, [src2], #8
| /*
| * We can not add limit with alignment offset(tmp1) here. Since the
| * addition probably make the limit overflown.
| */
| sub limit_wd, limit, #1/*limit != 0, so no underflow.*/
| and tmp3, limit_wd, #7
| lsr limit_wd, limit_wd, #3
| add tmp3, tmp3, tmp1
| add limit_wd, limit_wd, tmp3, lsr #3
| add limit, limit, tmp1/* Adjust the limit for the extra. */
|
| lsl tmp1, tmp1, #3/* Bytes beyond alignment -> bits.*/
| neg tmp1, tmp1/* Bits to alignment -64. */
| mov tmp2, #~0
| /*mask off the non-intended bytes before the start address.*/
| CPU_BE( lsl tmp2, tmp2, tmp1 )/*Big-endian.Early bytes are at MSB*/
| /* Little-endian. Early bytes are at LSB. */
| CPU_LE( lsr tmp2, tmp2, tmp1 )
|
| orr data1, data1, tmp2
| orr data2, data2, tmp2
| b .Lstart_realigned
|
| /*src1 and src2 have different alignment offset.*/
| .Lmisaligned8:
| cmp limit, #8
| b.lo .Ltiny8proc /*limit < 8: compare byte by byte*/
|
| and tmp1, src1, #7
| neg tmp1, tmp1
| add tmp1, tmp1, #8/*valid length in the first 8 bytes of src1*/
| and tmp2, src2, #7
| neg tmp2, tmp2
| add tmp2, tmp2, #8/*valid length in the first 8 bytes of src2*/
| subs tmp3, tmp1, tmp2
| csel pos, tmp1, tmp2, hi /*Choose the maximum.*/
|
| sub limit, limit, pos
| /*compare the proceeding bytes in the first 8 byte segment.*/
| .Ltinycmp:
| ldrb data1w, [src1], #1
| ldrb data2w, [src2], #1
| subs pos, pos, #1
| ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
| b.eq .Ltinycmp
| cbnz pos, 1f /*diff occurred before the last byte.*/
| cmp data1w, data2w
| b.eq .Lstart_align
| 1:
| sub result, data1, data2
| ret
|
| .Lstart_align:
| lsr limit_wd, limit, #3
| cbz limit_wd, .Lremain8
|
| ands xzr, src1, #7
| b.eq .Lrecal_offset
| /*process more leading bytes to make src1 aligned...*/
| add src1, src1, tmp3 /*backwards src1 to alignment boundary*/
| add src2, src2, tmp3
| sub limit, limit, tmp3
| lsr limit_wd, limit, #3
| cbz limit_wd, .Lremain8
| /*load 8 bytes from aligned SRC1..*/
| ldr data1, [src1], #8
| ldr data2, [src2], #8
|
| subs limit_wd, limit_wd, #1
| eor diff, data1, data2 /*Non-zero if differences found.*/
| csinv endloop, diff, xzr, ne
| cbnz endloop, .Lunequal_proc
| /*How far is the current SRC2 from the alignment boundary...*/
| and tmp3, tmp3, #7
|
| .Lrecal_offset:/*src1 is aligned now..*/
| neg pos, tmp3
| .Lloopcmp_proc:
| /*
| * Divide the eight bytes into two parts. First,backwards the src2
| * to an alignment boundary,load eight bytes and compare from
| * the SRC2 alignment boundary. If all 8 bytes are equal,then start
| * the second part's comparison. Otherwise finish the comparison.
| * This special handle can garantee all the accesses are in the
| * thread/task space in avoid to overrange access.
| */
| ldr data1, [src1,pos]
| ldr data2, [src2,pos]
| eor diff, data1, data2 /* Non-zero if differences found. */
| cbnz diff, .Lnot_limit
|
| /*The second part process*/
| ldr data1, [src1], #8
| ldr data2, [src2], #8
| eor diff, data1, data2 /* Non-zero if differences found. */
| subs limit_wd, limit_wd, #1
| csinv endloop, diff, xzr, ne/*if limit_wd is 0,will finish the cmp*/
| cbz endloop, .Lloopcmp_proc
| .Lunequal_proc:
| cbz diff, .Lremain8
|
| /* There is difference occurred in the latest comparison. */
| .Lnot_limit:
| /*
| * For little endian,reverse the low significant equal bits into MSB,then
| * following CLZ can find how many equal bits exist.
| */
| CPU_LE( rev diff, diff )
| CPU_LE( rev data1, data1 )
| CPU_LE( rev data2, data2 )
|
| /*
| * The MS-non-zero bit of DIFF marks either the first bit
| * that is different, or the end of the significant data.
| * Shifting left now will bring the critical information into the
| * top bits.
| */
| clz pos, diff
| lsl data1, data1, pos
| lsl data2, data2, pos
| /*
| * We need to zero-extend (char is unsigned) the value and then
| * perform a signed subtraction.
| */
| lsr data1, data1, #56
| sub result, data1, data2, lsr #56
| ret
|
| .Lremain8:
| /* Limit % 8 == 0 =>. all data are equal.*/
| ands limit, limit, #7
| b.eq .Lret0
|
| .Ltiny8proc:
| ldrb data1w, [src1], #1
| ldrb data2w, [src2], #1
| subs limit, limit, #1
|
| ccmp data1w, data2w, #0, ne /* NZCV = 0b0000. */
| b.eq .Ltiny8proc
| sub result, data1, data2
| ret
| .Lret0:
| mov result, #0
| ret
| SYM_FUNC_END_PI(memcmp)
| EXPORT_SYMBOL_NOKASAN(memcmp)
|
|
