diff options
Diffstat (limited to 'libmp/Plan9-mips/mpvecdigmulsub.s')
| -rw-r--r-- | libmp/Plan9-mips/mpvecdigmulsub.s | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/libmp/Plan9-mips/mpvecdigmulsub.s b/libmp/Plan9-mips/mpvecdigmulsub.s new file mode 100644 index 00000000..c1a1739c --- /dev/null +++ b/libmp/Plan9-mips/mpvecdigmulsub.s @@ -0,0 +1,61 @@ +/* + * mpvecdigmulsub(mpdigit *b, int n, mpdigit m, mpdigit *p) + * + * p -= b*m + * + * each step looks like: + * hi,lo = m*b[i] + * lo += oldhi + carry + * hi += carry + * p[i] += lo + * oldhi = hi + * + * the registers are: + * b = R1 + * n = R4 + * m = R5 + * p = R6 + * i = R7 + * hi = R8 - constrained by hardware + * lo = R9 - constrained by hardware + * oldhi = R10 + * tmp = R11 + * + */ +TEXT mpvecdigmulsub(SB),$0 + + MOVW n+4(FP),R4 + MOVW m+8(FP),R5 + MOVW p+12(FP),R6 + + MOVW R0, R10 /* oldhi = 0 */ +_mulsubloop: + MOVW 0(R1), R9 /* lo = b[i] */ + ADDU $4, R1 + MOVW 0(R6), R11 /* tmp = p[i] */ + MULU R9, R5 + MOVW HI, R8 /* hi = (b[i] * m)>>32 */ + MOVW LO, R9 /* lo = b[i] * m */ + ADDU R10, R9 /* lo += oldhi */ + SGTU R10, R9, R2 + ADDU R2, R8 /* hi += carry */ + SUBU R9, R11, R3 /* tmp -= lo */ + SGTU R3, R11, R2 + ADDU R2, R8 /* hi += carry */ + MOVW R3, 0(R6) /* p[i] = tmp */ + ADDU $4, R6 + MOVW R8, R10 /* oldhi = hi */ + SUBU $1, R4 + BNE R4, _mulsubloop + + MOVW 0(R6), R11 /* tmp = p[i] */ + SUBU R10, R11, R3 /* tmp -= oldhi */ + MOVW R3, 0(R6) /* p[i] = tmp */ + SGTU R3, R11, R1 + BNE R1, _mulsub2 + MOVW $1, R1 /* return +1 for positive result */ + RET + +_mulsub2: + MOVW $-1, R1 /* return -1 for negative result */ + RET |