ref: b4c916efce5e1476d9ac7079ca8ffec54fdcbce2
dir: /sys/src/libc/arm/memmove.s/
TS = 0 TE = 1 FROM = 2 N = 3 TMP = 3 /* N and TMP don't overlap */ TMP1 = 4 TEXT memcpy(SB), $0 B _memmove TEXT memmove(SB), $0 _memmove: MOVW R(TS), to+0(FP) /* need to save for return value */ MOVW from+4(FP), R(FROM) MOVW n+8(FP), R(N) ADD R(N), R(TS), R(TE) /* to end pointer */ CMP R(FROM), R(TS) BLS _forward _back: ADD R(N), R(FROM) /* from end pointer */ CMP $4, R(N) /* need at least 4 bytes to copy */ BLT _b1tail _b4align: /* align destination on 4 */ AND.S $3, R(TE), R(TMP) BEQ _b4aligned MOVBU.W -1(R(FROM)), R(TMP) /* pre-indexed */ MOVBU.W R(TMP), -1(R(TE)) /* pre-indexed */ B _b4align _b4aligned: /* is source now aligned? */ AND.S $3, R(FROM), R(TMP) BNE _bunaligned ADD $31, R(TS), R(TMP) /* do 32-byte chunks if possible */ _b32loop: CMP R(TMP), R(TE) BLS _b4tail MOVM.DB.W (R(FROM)), [R4-R7] MOVM.DB.W [R4-R7], (R(TE)) MOVM.DB.W (R(FROM)), [R4-R7] MOVM.DB.W [R4-R7], (R(TE)) B _b32loop _b4tail: /* do remaining words if possible */ ADD $3, R(TS), R(TMP) _b4loop: CMP R(TMP), R(TE) BLS _b1tail MOVW.W -4(R(FROM)), R(TMP1) /* pre-indexed */ MOVW.W R(TMP1), -4(R(TE)) /* pre-indexed */ B _b4loop _b1tail: /* remaining bytes */ CMP R(TE), R(TS) BEQ _return MOVBU.W -1(R(FROM)), R(TMP) /* pre-indexed */ MOVBU.W R(TMP), -1(R(TE)) /* pre-indexed */ B _b1tail _forward: CMP $4, R(N) /* need at least 4 bytes to copy */ BLT _f1tail _f4align: /* align destination on 4 */ AND.S $3, R(TS), R(TMP) BEQ _f4aligned MOVBU.P 1(R(FROM)), R(TMP) /* implicit write back */ MOVBU.P R(TMP), 1(R(TS)) /* implicit write back */ B _f4align _f4aligned: /* is source now aligned? */ AND.S $3, R(FROM), R(TMP) BNE _funaligned SUB $31, R(TE), R(TMP) /* do 32-byte chunks if possible */ _f32loop: CMP R(TMP), R(TS) BHS _f4tail MOVM.IA.W (R(FROM)), [R4-R7] MOVM.IA.W [R4-R7], (R(TS)) MOVM.IA.W (R(FROM)), [R4-R7] MOVM.IA.W [R4-R7], (R(TS)) B _f32loop _f4tail: SUB $3, R(TE), R(TMP) /* do remaining words if possible */ _f4loop: CMP R(TMP), R(TS) BHS _f1tail MOVW.P 4(R(FROM)), R(TMP1) /* implicit write back */ MOVW.P R4, 4(R(TS)) /* implicit write back */ B _f4loop _f1tail: CMP R(TS), R(TE) BEQ _return MOVBU.P 1(R(FROM)), R(TMP) /* implicit write back */ MOVBU.P R(TMP), 1(R(TS)) /* implicit write back */ B _f1tail _return: MOVW to+0(FP), R0 RET RSHIFT = 4 LSHIFT = 5 OFFSET = 11 BR0 = 6 BW0 = 7 BR1 = 7 BW1 = 8 _bunaligned: CMP $2, R(TMP) /* is R(TMP) < 2 ? */ MOVW.LT $8, R(RSHIFT) /* (R(n)<<24)|(R(n-1)>>8) */ MOVW.LT $24, R(LSHIFT) MOVW.LT $1, R(OFFSET) MOVW.EQ $16, R(RSHIFT) /* (R(n)<<16)|(R(n-1)>>16) */ MOVW.EQ $16, R(LSHIFT) MOVW.EQ $2, R(OFFSET) MOVW.GT $24, R(RSHIFT) /* (R(n)<<8)|(R(n-1)>>24) */ MOVW.GT $8, R(LSHIFT) MOVW.GT $3, R(OFFSET) ADD $8, R(TS), R(TMP) /* do 8-byte chunks if possible */ CMP R(TMP), R(TE) BLS _b1tail BIC $3, R(FROM) /* align source */ MOVW (R(FROM)), R(BR0) /* prime first block register */ _bu8loop: CMP R(TMP), R(TE) BLS _bu1tail MOVW R(BR0)<<R(LSHIFT), R(BW1) MOVM.DB.W (R(FROM)), [R(BR0)-R(BR1)] ORR R(BR1)>>R(RSHIFT), R(BW1) MOVW R(BR1)<<R(LSHIFT), R(BW0) ORR R(BR0)>>R(RSHIFT), R(BW0) MOVM.DB.W [R(BW0)-R(BW1)], (R(TE)) B _bu8loop _bu1tail: ADD R(OFFSET), R(FROM) B _b1tail RSHIFT = 4 LSHIFT = 5 OFFSET = 11 FW0 = 6 FR0 = 7 FW1 = 7 FR1 = 8 _funaligned: CMP $2, R(TMP) MOVW.LT $8, R(RSHIFT) /* (R(n+1)<<24)|(R(n)>>8) */ MOVW.LT $24, R(LSHIFT) MOVW.LT $3, R(OFFSET) MOVW.EQ $16, R(RSHIFT) /* (R(n+1)<<16)|(R(n)>>16) */ MOVW.EQ $16, R(LSHIFT) MOVW.EQ $2, R(OFFSET) MOVW.GT $24, R(RSHIFT) /* (R(n+1)<<8)|(R(n)>>24) */ MOVW.GT $8, R(LSHIFT) MOVW.GT $1, R(OFFSET) SUB $8, R(TE), R(TMP) /* do 8-byte chunks if possible */ CMP R(TMP), R(TS) BHS _f1tail BIC $3, R(FROM) /* align source */ MOVW.P 4(R(FROM)), R(FR1) /* prime last block register, implicit write back */ _fu8loop: CMP R(TMP), R(TS) BHS _fu1tail MOVW R(FR1)>>R(RSHIFT), R(FW0) MOVM.IA.W (R(FROM)), [R(FR0)-R(FR1)] ORR R(FR0)<<R(LSHIFT), R(FW0) MOVW R(FR0)>>R(RSHIFT), R(FW1) ORR R(FR1)<<R(LSHIFT), R(FW1) MOVM.IA.W [R(FW0)-R(FW1)], (R(TS)) B _fu8loop _fu1tail: SUB R(OFFSET), R(FROM) B _f1tail