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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 two strings
| *
| * Parameters:
| * x0 - const string 1 pointer
| * x1 - const string 2 pointer
| * Returns:
| * x0 - an integer less than, equal to, or greater than zero
| * if s1 is found, respectively, to be less than, to match,
| * or be greater than s2.
| */
|
| #define REP8_01 0x0101010101010101
| #define REP8_7f 0x7f7f7f7f7f7f7f7f
| #define REP8_80 0x8080808080808080
|
| /* Parameters and result. */
| src1 .req x0
| src2 .req x1
| result .req x0
|
| /* Internal variables. */
| data1 .req x2
| data1w .req w2
| data2 .req x3
| data2w .req w3
| has_nul .req x4
| diff .req x5
| syndrome .req x6
| tmp1 .req x7
| tmp2 .req x8
| tmp3 .req x9
| zeroones .req x10
| pos .req x11
|
| SYM_FUNC_START_WEAK_PI(strcmp)
| eor tmp1, src1, src2
| mov zeroones, #REP8_01
| tst tmp1, #7
| b.ne .Lmisaligned8
| ands tmp1, src1, #7
| b.ne .Lmutual_align
|
| /*
| * NUL detection works on the principle that (X - 1) & (~X) & 0x80
| * (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
| * can be done in parallel across the entire word.
| */
| .Lloop_aligned:
| ldr data1, [src1], #8
| ldr data2, [src2], #8
| .Lstart_realigned:
| sub tmp1, data1, zeroones
| orr tmp2, data1, #REP8_7f
| eor diff, data1, data2 /* Non-zero if differences found. */
| bic has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */
| orr syndrome, diff, has_nul
| cbz syndrome, .Lloop_aligned
| b .Lcal_cmpresult
|
| .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 preceed the start point.
| */
| bic src1, src1, #7
| bic src2, src2, #7
| lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
| ldr data1, [src1], #8
| neg tmp1, tmp1 /* Bits to alignment -64. */
| ldr data2, [src2], #8
| mov tmp2, #~0
| /* Big-endian. Early bytes are at MSB. */
| CPU_BE( lsl tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
| /* Little-endian. Early bytes are at LSB. */
| CPU_LE( lsr tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */
|
| orr data1, data1, tmp2
| orr data2, data2, tmp2
| b .Lstart_realigned
|
| .Lmisaligned8:
| /*
| * Get the align offset length to compare per byte first.
| * After this process, one string's address will be aligned.
| */
| and tmp1, src1, #7
| neg tmp1, tmp1
| add tmp1, tmp1, #8
| and tmp2, src2, #7
| neg tmp2, tmp2
| add tmp2, tmp2, #8
| subs tmp3, tmp1, tmp2
| csel pos, tmp1, tmp2, hi /*Choose the maximum. */
| .Ltinycmp:
| ldrb data1w, [src1], #1
| ldrb data2w, [src2], #1
| subs pos, pos, #1
| ccmp data1w, #1, #0, ne /* NZCV = 0b0000. */
| ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
| b.eq .Ltinycmp
| cbnz pos, 1f /*find the null or unequal...*/
| cmp data1w, #1
| ccmp data1w, data2w, #0, cs
| b.eq .Lstart_align /*the last bytes are equal....*/
| 1:
| sub result, data1, data2
| ret
|
| .Lstart_align:
| ands xzr, src1, #7
| b.eq .Lrecal_offset
| /*process more leading bytes to make str1 aligned...*/
| add src1, src1, tmp3
| add src2, src2, tmp3
| /*load 8 bytes from aligned str1 and non-aligned str2..*/
| ldr data1, [src1], #8
| ldr data2, [src2], #8
|
| sub tmp1, data1, zeroones
| orr tmp2, data1, #REP8_7f
| bic has_nul, tmp1, tmp2
| eor diff, data1, data2 /* Non-zero if differences found. */
| orr syndrome, diff, has_nul
| cbnz syndrome, .Lcal_cmpresult
| /*How far is the current str2 from the alignment boundary...*/
| and tmp3, tmp3, #7
| .Lrecal_offset:
| neg pos, tmp3
| .Lloopcmp_proc:
| /*
| * Divide the eight bytes into two parts. First,backwards the src2
| * to an alignment boundary,load eight bytes from the SRC2 alignment
| * boundary,then compare with the relative bytes from SRC1.
| * 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]
| sub tmp1, data1, zeroones
| orr tmp2, data1, #REP8_7f
| bic has_nul, tmp1, tmp2
| eor diff, data1, data2 /* Non-zero if differences found. */
| orr syndrome, diff, has_nul
| cbnz syndrome, .Lcal_cmpresult
|
| /*The second part process*/
| ldr data1, [src1], #8
| ldr data2, [src2], #8
| sub tmp1, data1, zeroones
| orr tmp2, data1, #REP8_7f
| bic has_nul, tmp1, tmp2
| eor diff, data1, data2 /* Non-zero if differences found. */
| orr syndrome, diff, has_nul
| cbz syndrome, .Lloopcmp_proc
|
| .Lcal_cmpresult:
| /*
| * reversed the byte-order as big-endian,then CLZ can find the most
| * significant zero bits.
| */
| CPU_LE( rev syndrome, syndrome )
| CPU_LE( rev data1, data1 )
| CPU_LE( rev data2, data2 )
|
| /*
| * For big-endian we cannot use the trick with the syndrome value
| * as carry-propagation can corrupt the upper bits if the trailing
| * bytes in the string contain 0x01.
| * However, if there is no NUL byte in the dword, we can generate
| * the result directly. We cannot just subtract the bytes as the
| * MSB might be significant.
| */
| CPU_BE( cbnz has_nul, 1f )
| CPU_BE( cmp data1, data2 )
| CPU_BE( cset result, ne )
| CPU_BE( cneg result, result, lo )
| CPU_BE( ret )
| CPU_BE( 1: )
| /*Re-compute the NUL-byte detection, using a byte-reversed value. */
| CPU_BE( rev tmp3, data1 )
| CPU_BE( sub tmp1, tmp3, zeroones )
| CPU_BE( orr tmp2, tmp3, #REP8_7f )
| CPU_BE( bic has_nul, tmp1, tmp2 )
| CPU_BE( rev has_nul, has_nul )
| CPU_BE( orr syndrome, diff, has_nul )
|
| clz pos, syndrome
| /*
| * The MS-non-zero bit of the syndrome marks either the first bit
| * that is different, or the top bit of the first zero byte.
| * Shifting left now will bring the critical information into the
| * top bits.
| */
| lsl data1, data1, pos
| lsl data2, data2, pos
| /*
| * But we need to zero-extend (char is unsigned) the value and then
| * perform a signed 32-bit subtraction.
| */
| lsr data1, data1, #56
| sub result, data1, data2, lsr #56
| ret
| SYM_FUNC_END_PI(strcmp)
| EXPORT_SYMBOL_NOKASAN(strcmp)
|
|
