122 строки
2.3 KiB
ArmAsm
122 строки
2.3 KiB
ArmAsm
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/* Optimised simple memory fill
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*
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <asm/cache.h>
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.section .text
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.balign L1_CACHE_BYTES
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###############################################################################
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#
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# void *memset(void *dst, int c, size_t n)
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#
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###############################################################################
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.globl memset
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.type memset,@function
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memset:
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movm [d2,d3],(sp)
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mov d0,(12,sp)
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mov d1,(16,sp)
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mov (20,sp),d2 # count
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mov d0,a0 # dst
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mov d0,e3 # the return value
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cmp +0,d2
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beq memset_done # return if zero-length fill
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# see if the region parameters are four-byte aligned
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or d0,d2,d3
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and +3,d3
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bne memset_1 # jump if not
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extbu d1
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mov_asl d1,d3,8,d1
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or_asl d1,d3,8,d1
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or_asl d1,d3,8,d1
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or d3,d1
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# we want to transfer as much as we can in chunks of 32 bytes
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cmp +31,d2
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bls memset_4_remainder # 4-byte aligned remainder
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add -32,d2
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mov +32,d3
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memset_4_loop:
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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sub d3,d2
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bcc memset_4_loop
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add d3,d2
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beq memset_4_no_remainder
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memset_4_remainder:
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# cut 4-7 words down to 0-3
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cmp +16,d2
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bcs memset_4_three_or_fewer_words
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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mov d1,(a0+)
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add -16,d2
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beq memset_4_no_remainder
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# copy the remaining 1, 2 or 3 words
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memset_4_three_or_fewer_words:
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cmp +8,d2
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bcs memset_4_one_word
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beq memset_4_two_words
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mov d1,(a0+)
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memset_4_two_words:
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mov d1,(a0+)
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memset_4_one_word:
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mov d1,(a0+)
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memset_4_no_remainder:
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# check we set the correct amount
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# TODO: REMOVE CHECK
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sub e3,a0,d2
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mov (20,sp),d1
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cmp d2,d1
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beq memset_done
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break
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break
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break
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memset_done:
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mov e3,a0
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ret [d2,d3],8
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# handle misaligned copying
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memset_1:
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add -1,d2
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mov +1,d3
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setlb # setlb requires the next insns
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# to occupy exactly 4 bytes
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sub d3,d2
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movbu d1,(a0)
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inc a0
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lcc
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mov e3,a0
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ret [d2,d3],8
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memset_end:
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.size memset, memset_end-memset
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