diff options
Diffstat (limited to 'libmp/Plan9-386/mpvecdigmulsub.s')
| -rw-r--r-- | libmp/Plan9-386/mpvecdigmulsub.s | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/libmp/Plan9-386/mpvecdigmulsub.s b/libmp/Plan9-386/mpvecdigmulsub.s new file mode 100644 index 00000000..ab28ef03 --- /dev/null +++ b/libmp/Plan9-386/mpvecdigmulsub.s @@ -0,0 +1,53 @@ +/* + * mpvecdigmulsub(mpdigit *b, int n, mpdigit m, mpdigit *p) + * + * p -= b*m + * + * each step look like: + * hi,lo = m*b[i] + * lo += oldhi + carry + * hi += carry + * p[i] += lo + * oldhi = hi + * + * the registers are: + * hi = DX - constrained by hardware + * lo = AX - constrained by hardware + * b = SI - can't be BP + * p = DI - can't be BP + * i = BP + * n = CX - constrained by LOOP instr + * m = BX + * oldhi = EX + * + */ +TEXT mpvecdigmulsub(SB),$0 + + MOVL b+0(FP),SI + MOVL n+4(FP),CX + MOVL m+8(FP),BX + MOVL p+12(FP),DI + XORL BP,BP + PUSHL BP +_mulsubloop: + MOVL (SI)(BP*4),AX /* lo = b[i] */ + MULL BX /* hi, lo = b[i] * m */ + ADDL 0(SP),AX /* lo += oldhi */ + JCC _mulsubnocarry1 + INCL DX /* hi += carry */ +_mulsubnocarry1: + SUBL AX,(DI)(BP*4) + JCC _mulsubnocarry2 + INCL DX /* hi += carry */ +_mulsubnocarry2: + MOVL DX,0(SP) + INCL BP + LOOP _mulsubloop + POPL AX + SUBL AX,(DI)(BP*4) + JCC _mulsubnocarry3 + MOVL $-1,AX + RET +_mulsubnocarry3: + MOVL $1,AX + RET |