33 lines
875 B
ArmAsm
33 lines
875 B
ArmAsm
.file "memchr.S"
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.section .text
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.global _memchr
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.type _memchr,@function
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_memchr:
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;; R1: string pointer
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;; R2: byte sought
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;; R3: max number to scan
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#ifdef __RX_DISALLOW_STRING_INSNS__
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mov.b r2, r2 ; The mov.b below sign extends as it loads, so make sure that r2 is sign-extended as well.
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2: cmp #0, r3
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beq 1f
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sub #1, r3
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mov.b [r1+], r5
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cmp r5, r2
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bne 2b
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sub #1, r1 ; We have found a match, bit now R1 points to the byte after the match.
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1: rts
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#else
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cmp #0, r3 ; If r3 is 0 suntil.b will do nothing and not set any flags...
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stz #1, r1 ; ...so store 1 into r1. It will be decremented by the SUB later.
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suntil.b ; Search until *r1 == r2 or r3 bytes have been examined.
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stnz #1, r1 ; If no match was found return NULL.
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sub #1, r1 ; suntil.b leaves r1 pointing at the address *after* the match.
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rts
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#endif
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.size _memchr, . - _memchr
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