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133 lines
3.1 KiB
ArmAsm
133 lines
3.1 KiB
ArmAsm
/* memcmp - compare memory
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*
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* Copyright (c) 2013, Arm Limited.
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* SPDX-License-Identifier: MIT
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*/
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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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#include "asmdefs.h"
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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 data1h x4
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#define data2 x5
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#define data2w w5
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#define data2h x6
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#define tmp1 x7
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#define tmp2 x8
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ENTRY (memcmp)
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subs limit, limit, 8
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b.lo L(less8)
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ldr data1, [src1], 8
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ldr data2, [src2], 8
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cmp data1, data2
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b.ne L(return)
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subs limit, limit, 8
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b.gt L(more16)
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ldr data1, [src1, limit]
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ldr data2, [src2, limit]
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b L(return)
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L(more16):
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ldr data1, [src1], 8
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ldr data2, [src2], 8
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cmp data1, data2
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bne L(return)
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/* Jump directly to comparing the last 16 bytes for 32 byte (or less)
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strings. */
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subs limit, limit, 16
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b.ls L(last_bytes)
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/* We overlap loads between 0-32 bytes at either side of SRC1 when we
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try to align, so limit it only to strings larger than 128 bytes. */
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cmp limit, 96
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b.ls L(loop16)
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/* Align src1 and adjust src2 with bytes not yet done. */
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and tmp1, src1, 15
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add limit, limit, tmp1
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sub src1, src1, tmp1
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sub src2, src2, tmp1
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/* Loop performing 16 bytes per iteration using aligned src1.
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Limit is pre-decremented by 16 and must be larger than zero.
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Exit if <= 16 bytes left to do or if the data is not equal. */
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.p2align 4
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L(loop16):
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ldp data1, data1h, [src1], 16
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ldp data2, data2h, [src2], 16
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subs limit, limit, 16
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ccmp data1, data2, 0, hi
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ccmp data1h, data2h, 0, eq
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b.eq L(loop16)
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cmp data1, data2
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bne L(return)
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mov data1, data1h
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mov data2, data2h
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cmp data1, data2
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bne L(return)
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/* Compare last 1-16 bytes using unaligned access. */
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L(last_bytes):
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add src1, src1, limit
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add src2, src2, limit
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ldp data1, data1h, [src1]
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ldp data2, data2h, [src2]
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cmp data1, data2
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bne L(return)
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mov data1, data1h
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mov data2, data2h
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cmp data1, data2
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/* Compare data bytes and set return value to 0, -1 or 1. */
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L(return):
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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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L(ret_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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L(less8):
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adds limit, limit, 4
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b.lo L(less4)
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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 L(return)
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sub limit, limit, 4
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L(less4):
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adds limit, limit, 4
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beq L(ret_eq)
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L(byte_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 L(byte_loop)
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sub result, data1w, data2w
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ret
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END (memcmp)
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