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141 lines
4.0 KiB
ArmAsm
141 lines
4.0 KiB
ArmAsm
/*
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* Copyright (c) 2017 ARM Ltd
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the company may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#if (defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED))
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/* See memcmp-stub.c */
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#else
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/* Assumptions:
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*
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* ARMv8-a, AArch64, unaligned accesses.
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*/
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/* Parameters and result. */
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#define src1 x0
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#define src2 x1
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#define limit x2
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#define result w0
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/* Internal variables. */
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#define data1 x3
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#define data1w w3
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#define data2 x4
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#define data2w w4
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#define tmp1 x5
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.macro def_fn f p2align=0
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.text
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.p2align \p2align
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.global \f
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.type \f, %function
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\f:
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.endm
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/* Small inputs of less than 8 bytes are handled separately. This allows the
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main code to be sped up using unaligned loads since there are now at least
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8 bytes to be compared. If the first 8 bytes are equal, align src1.
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This ensures each iteration does at most one unaligned access even if both
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src1 and src2 are unaligned, and mutually aligned inputs behave as if
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aligned. After the main loop, process the last 8 bytes using unaligned
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accesses. */
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def_fn memcmp p2align=6
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subs limit, limit, 8
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b.lo .Lless8
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/* Limit >= 8, so check first 8 bytes using unaligned loads. */
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ldr data1, [src1], 8
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ldr data2, [src2], 8
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and tmp1, src1, 7
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add limit, limit, tmp1
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cmp data1, data2
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bne .Lreturn
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/* Align src1 and adjust src2 with bytes not yet done. */
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sub src1, src1, tmp1
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sub src2, src2, tmp1
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subs limit, limit, 8
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b.ls .Llast_bytes
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/* Loop performing 8 bytes per iteration using aligned src1.
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Limit is pre-decremented by 8 and must be larger than zero.
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Exit if <= 8 bytes left to do or if the data is not equal. */
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.p2align 4
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.Lloop8:
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ldr data1, [src1], 8
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ldr data2, [src2], 8
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subs limit, limit, 8
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ccmp data1, data2, 0, hi /* NZCV = 0b0000. */
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b.eq .Lloop8
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cmp data1, data2
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bne .Lreturn
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/* Compare last 1-8 bytes using unaligned access. */
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.Llast_bytes:
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ldr data1, [src1, limit]
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ldr data2, [src2, limit]
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/* Compare data bytes and set return value to 0, -1 or 1. */
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.Lreturn:
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#ifndef __AARCH64EB__
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rev data1, data1
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rev data2, data2
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#endif
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cmp data1, data2
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.Lret_eq:
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cset result, ne
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cneg result, result, lo
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ret
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.p2align 4
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/* Compare up to 8 bytes. Limit is [-8..-1]. */
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.Lless8:
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adds limit, limit, 4
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b.lo .Lless4
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ldr data1w, [src1], 4
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ldr data2w, [src2], 4
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cmp data1w, data2w
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b.ne .Lreturn
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sub limit, limit, 4
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.Lless4:
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adds limit, limit, 4
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beq .Lret_eq
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.Lbyte_loop:
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ldrb data1w, [src1], 1
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ldrb data2w, [src2], 1
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subs limit, limit, 1
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ccmp data1w, data2w, 0, ne /* NZCV = 0b0000. */
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b.eq .Lbyte_loop
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sub result, data1w, data2w
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ret
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.size memcmp, . - memcmp
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#endif
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