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arm64: Import latest version of Cortex Strings' strcmp
Import the latest version of the former Cortex Strings - now Arm Optimized Routines - strcmp function based on the upstream code of string/aarch64/strcmp.S at commit afd6244 from https://github.com/ARM-software/optimized-routines Note that for simplicity Arm have chosen to contribute this code to Linux under GPLv2 rather than the original MIT license. Signed-off-by: Sam Tebbs <sam.tebbs@arm.com> [ rm: update attribution and commit message ] Signed-off-by: Robin Murphy <robin.murphy@arm.com> Link: https://lore.kernel.org/r/0fe90c90b96b569fbdfd46e47bd1298abb02079e.1622128527.git.robin.murphy@arm.com Signed-off-by: Will Deacon <will@kernel.org>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,223 +1,176 @@ | ||
| /* SPDX-License-Identifier: GPL-2.0-only */ | ||
| /* | ||
| * Copyright (C) 2013 ARM Ltd. | ||
| * Copyright (C) 2013 Linaro. | ||
| * Copyright (c) 2012-2020, Arm Limited. | ||
| * | ||
| * 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/ | ||
| * Adapted from the original at: | ||
| * https://github.com/ARM-software/optimized-routines/blob/master/string/aarch64/strcmp.S | ||
| */ | ||
|
|
||
| #include <linux/linkage.h> | ||
| #include <asm/assembler.h> | ||
|
|
||
| /* | ||
| * compare two strings | ||
| /* Assumptions: | ||
| * | ||
| * 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. | ||
| * ARMv8-a, AArch64 | ||
| */ | ||
|
|
||
| #define L(label) .L ## label | ||
|
|
||
| #define REP8_01 0x0101010101010101 | ||
| #define REP8_7f 0x7f7f7f7f7f7f7f7f | ||
| #define REP8_80 0x8080808080808080 | ||
|
|
||
| /* Parameters and result. */ | ||
| src1 .req x0 | ||
| src2 .req x1 | ||
| result .req x0 | ||
| #define src1 x0 | ||
| #define src2 x1 | ||
| #define result 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 | ||
|
|
||
| #define data1 x2 | ||
| #define data1w w2 | ||
| #define data2 x3 | ||
| #define data2w w3 | ||
| #define has_nul x4 | ||
| #define diff x5 | ||
| #define syndrome x6 | ||
| #define tmp1 x7 | ||
| #define tmp2 x8 | ||
| #define tmp3 x9 | ||
| #define zeroones x10 | ||
| #define pos x11 | ||
|
|
||
| /* Start of performance-critical section -- one 64B cache line. */ | ||
| .align 6 | ||
| SYM_FUNC_START_WEAK_PI(strcmp) | ||
| eor tmp1, src1, src2 | ||
| mov zeroones, #REP8_01 | ||
| tst tmp1, #7 | ||
| b.ne .Lmisaligned8 | ||
| b.ne L(misaligned8) | ||
| 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: | ||
| b.ne L(mutual_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. */ | ||
| L(loop_aligned): | ||
| ldr data1, [src1], #8 | ||
| ldr data2, [src2], #8 | ||
| .Lstart_realigned: | ||
| L(start_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 | ||
| cbz syndrome, L(loop_aligned) | ||
| /* End of performance-critical section -- one 64B cache line. */ | ||
|
|
||
| L(end): | ||
| #ifndef __AARCH64EB__ | ||
| rev syndrome, syndrome | ||
| rev data1, data1 | ||
| /* 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. */ | ||
| clz pos, syndrome | ||
| rev data2, data2 | ||
| 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 | ||
| #else | ||
| /* 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 can't just subtract the bytes as the | ||
| MSB might be significant. */ | ||
| cbnz has_nul, 1f | ||
| cmp data1, data2 | ||
| cset result, ne | ||
| cneg result, result, lo | ||
| ret | ||
| 1: | ||
| /* Re-compute the NUL-byte detection, using a byte-reversed value. */ | ||
| rev tmp3, data1 | ||
| sub tmp1, tmp3, zeroones | ||
| orr tmp2, tmp3, #REP8_7f | ||
| bic has_nul, tmp1, tmp2 | ||
| rev has_nul, has_nul | ||
| 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 | ||
| #endif | ||
|
|
||
| .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. | ||
| */ | ||
| L(mutual_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 | ||
| #ifdef __AARCH64EB__ | ||
| /* Big-endian. Early bytes are at MSB. */ | ||
| CPU_BE( lsl tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */ | ||
| lsl tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */ | ||
| #else | ||
| /* Little-endian. Early bytes are at LSB. */ | ||
| CPU_LE( lsr tmp2, tmp2, tmp1 ) /* Shift (tmp1 & 63). */ | ||
|
|
||
| lsr tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */ | ||
| #endif | ||
| 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: | ||
| b L(start_realigned) | ||
|
|
||
| L(misaligned8): | ||
| /* Align SRC1 to 8 bytes and then compare 8 bytes at a time, always | ||
| checking to make sure that we don't access beyond page boundary in | ||
| SRC2. */ | ||
| tst src1, #7 | ||
| b.eq L(loop_misaligned) | ||
| L(do_misaligned): | ||
| 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..*/ | ||
| ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */ | ||
| b.ne L(done) | ||
| tst src1, #7 | ||
| b.ne L(do_misaligned) | ||
|
|
||
| L(loop_misaligned): | ||
| /* Test if we are within the last dword of the end of a 4K page. If | ||
| yes then jump back to the misaligned loop to copy a byte at a time. */ | ||
| and tmp1, src2, #0xff8 | ||
| eor tmp1, tmp1, #0xff8 | ||
| cbz tmp1, L(do_misaligned) | ||
| 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. */ | ||
| 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, .Lloopcmp_proc | ||
| cbz syndrome, L(loop_misaligned) | ||
| b L(end) | ||
|
|
||
| .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 | ||
| L(done): | ||
| sub result, data1, data2 | ||
| ret | ||
|
|
||
| SYM_FUNC_END_PI(strcmp) | ||
| EXPORT_SYMBOL_NOKASAN(strcmp) |