82 lines
1.1 KiB
ArmAsm
82 lines
1.1 KiB
ArmAsm
TEXT memcpy(SB), $0
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MOVQ RARG, DI
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MOVQ DI, AX /* return value */
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MOVQ p2+8(FP), SI
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MOVQ n+16(FP), BX
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CMPQ BX, $0
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JGT _ok
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JEQ _return /* nothing to do if n == 0 */
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MOVL $0, SI /* fault if n < 0 */
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/*
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* check and set for backwards:
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* (p2 < p1) && ((p2+n) > p1)
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*/
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_ok:
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CMPQ SI, DI
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JGT _forward
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JEQ _return /* nothing to do if p2 == p1 */
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MOVQ SI, DX
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ADDQ BX, DX
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CMPQ DX, DI
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JGT _back
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/*
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* copy whole longs if aligned
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*/
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_forward:
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CLD
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MOVQ SI, DX
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ORQ DI, DX
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ANDL $3, DX
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JNE c3f
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MOVQ BX, CX
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SHRQ $2, CX
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ANDL $3, BX
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REP; MOVSL
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/*
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* copy the rest, by bytes
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*/
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JEQ _return /* flags set by above ANDL */
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c3f:
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MOVQ BX, CX
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REP; MOVSB
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RET
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/*
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* whole thing backwards has
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* adjusted addresses
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*/
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_back:
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ADDQ BX, DI
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ADDQ BX, SI
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STD
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SUBQ $4, DI
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SUBQ $4, SI
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/*
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* copy whole longs, if aligned
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*/
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MOVQ DI, DX
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ORQ SI, DX
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ANDL $3, DX
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JNE c3b
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MOVQ BX, CX
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SHRQ $2, CX
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ANDL $3, BX
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REP; MOVSL
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/*
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* copy the rest, by bytes
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*/
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JEQ _return /* flags set by above ANDL */
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c3b:
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ADDQ $3, DI
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ADDQ $3, SI
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MOVQ BX, CX
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REP; MOVSB
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_return:
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RET
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