149 lines
3.8 KiB
ArmAsm
149 lines
3.8 KiB
ArmAsm
/*
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* arch/xtensa/lib/strnlen_user.S
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*
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* This file is subject to the terms and conditions of the GNU General
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* Public License. See the file "COPYING" in the main directory of
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* this archive for more details.
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*
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* Returns strnlen, including trailing zero terminator.
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* Zero indicates error.
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*
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* Copyright (C) 2002 Tensilica Inc.
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*/
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#include <asm/variant/core.h>
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/* Load or store instructions that may cause exceptions use the EX macro. */
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#define EX(insn,reg1,reg2,offset,handler) \
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9: insn reg1, reg2, offset; \
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.section __ex_table, "a"; \
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.word 9b, handler; \
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.previous
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/*
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* size_t __strnlen_user(const char *s, size_t len)
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*/
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#ifdef __XTENSA_EB__
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# define MASK0 0xff000000
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# define MASK1 0x00ff0000
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# define MASK2 0x0000ff00
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# define MASK3 0x000000ff
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#else
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# define MASK0 0x000000ff
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# define MASK1 0x0000ff00
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# define MASK2 0x00ff0000
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# define MASK3 0xff000000
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#endif
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# Register use:
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# a2/ src
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# a3/ len
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# a4/ tmp
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# a5/ mask0
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# a6/ mask1
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# a7/ mask2
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# a8/ mask3
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# a9/ tmp
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# a10/ tmp
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.text
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.align 4
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.global __strnlen_user
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.type __strnlen_user,@function
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__strnlen_user:
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entry sp, 16 # minimal stack frame
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# a2/ s, a3/ len
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addi a4, a2, -4 # because we overincrement at the end;
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# we compensate with load offsets of 4
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movi a5, MASK0 # mask for byte 0
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movi a6, MASK1 # mask for byte 1
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movi a7, MASK2 # mask for byte 2
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movi a8, MASK3 # mask for byte 3
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bbsi.l a2, 0, .L1mod2 # if only 8-bit aligned
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bbsi.l a2, 1, .L2mod4 # if only 16-bit aligned
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/*
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* String is word-aligned.
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*/
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.Laligned:
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srli a10, a3, 2 # number of loop iterations with 4B per loop
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#if XCHAL_HAVE_LOOPS
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loopnez a10, .Ldone
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#else
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beqz a10, .Ldone
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slli a10, a10, 2
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add a10, a10, a4 # a10 = end of last 4B chunk
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#endif /* XCHAL_HAVE_LOOPS */
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.Loop:
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EX(l32i, a9, a4, 4, lenfixup) # get next word of string
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addi a4, a4, 4 # advance string pointer
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bnone a9, a5, .Lz0 # if byte 0 is zero
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bnone a9, a6, .Lz1 # if byte 1 is zero
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bnone a9, a7, .Lz2 # if byte 2 is zero
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bnone a9, a8, .Lz3 # if byte 3 is zero
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#if !XCHAL_HAVE_LOOPS
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blt a4, a10, .Loop
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#endif
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.Ldone:
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EX(l32i, a9, a4, 4, lenfixup) # load 4 bytes for remaining checks
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bbci.l a3, 1, .L100
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# check two more bytes (bytes 0, 1 of word)
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addi a4, a4, 2 # advance string pointer
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bnone a9, a5, .Lz0 # if byte 0 is zero
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bnone a9, a6, .Lz1 # if byte 1 is zero
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.L100:
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bbci.l a3, 0, .L101
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# check one more byte (byte 2 of word)
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# Actually, we don't need to check. Zero or nonzero, we'll add one.
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# Do not add an extra one for the NULL terminator since we have
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# exhausted the original len parameter.
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addi a4, a4, 1 # advance string pointer
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.L101:
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sub a2, a4, a2 # compute length
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retw
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# NOTE that in several places below, we point to the byte just after
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# the zero byte in order to include the NULL terminator in the count.
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.Lz3: # byte 3 is zero
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addi a4, a4, 3 # point to zero byte
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.Lz0: # byte 0 is zero
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addi a4, a4, 1 # point just beyond zero byte
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sub a2, a4, a2 # subtract to get length
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retw
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.Lz1: # byte 1 is zero
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addi a4, a4, 1+1 # point just beyond zero byte
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sub a2, a4, a2 # subtract to get length
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retw
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.Lz2: # byte 2 is zero
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addi a4, a4, 2+1 # point just beyond zero byte
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sub a2, a4, a2 # subtract to get length
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retw
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.L1mod2: # address is odd
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EX(l8ui, a9, a4, 4, lenfixup) # get byte 0
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addi a4, a4, 1 # advance string pointer
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beqz a9, .Lz3 # if byte 0 is zero
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bbci.l a4, 1, .Laligned # if string pointer is now word-aligned
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.L2mod4: # address is 2 mod 4
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addi a4, a4, 2 # advance ptr for aligned access
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EX(l32i, a9, a4, 0, lenfixup) # get word with first two bytes of string
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bnone a9, a7, .Lz2 # if byte 2 (of word, not string) is zero
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bany a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero
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# byte 3 is zero
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addi a4, a4, 3+1 # point just beyond zero byte
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sub a2, a4, a2 # subtract to get length
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retw
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.section .fixup, "ax"
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.align 4
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lenfixup:
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movi a2, 0
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retw
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