diff options
Diffstat (limited to 'libmp/Plan9-mips/mpvecsub.s')
| -rw-r--r-- | libmp/Plan9-mips/mpvecsub.s | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/libmp/Plan9-mips/mpvecsub.s b/libmp/Plan9-mips/mpvecsub.s new file mode 100644 index 00000000..ca156fb7 --- /dev/null +++ b/libmp/Plan9-mips/mpvecsub.s @@ -0,0 +1,66 @@ +#define BDNZ BC 16,0, +#define BDNE BC 0,2, + +/* + * mpvecadd(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *sum) + * + * sum[0:alen] = a[0:alen-1] - b[0:blen-1] + * + * prereq: alen >= blen, sum has room for alen+1 digits + * + * R1 == a (first arg passed in R1) + * R3 == carry + * R4 == alen + * R5 == b + * R6 == blen + * R7 == sum + * R2 == temporary + * R8 == temporary + * R9 == temporary + */ +TEXT mpvecsub(SB),$-4 + + MOVW alen+4(FP), R4 + MOVW b+8(FP), R5 + MOVW blen+12(FP), R6 + MOVW sum+16(FP), R7 + SUBU R6, R4 /* calculate counter for second loop (alen > blen) */ + MOVW R0, R3 + + /* if blen == 0, don't need to subtract it */ + BEQ R6,_sub1 + + /* sum[0:blen-1],carry = a[0:blen-1] - b[0:blen-1] */ +_subloop1: + MOVW 0(R1), R8 + ADDU $4, R1 + MOVW 0(R5), R9 + ADDU $4, R5 + SUBU R3, R8, R2 + SGTU R2, R8, R3 + SUBU R9, R2, R8 + SGTU R8, R2, R9 + ADDU R9, R3 + MOVW R8, 0(R7) + ADDU $4, R7 + SUBU $1, R6 + BNE R6, _subloop1 + +_sub1: + /* if alen == blen, we're done */ + BEQ R4, _subend + + /* sum[blen:alen-1],carry = a[blen:alen-1] + 0 + carry */ +_subloop2: + MOVW 0(R1), R8 + ADDU $4, R1 + SUBU R3, R8, R2 + SGTU R2, R8, R3 + MOVW R2, 0(R7) + ADDU $4, R7 + SUBU $1, R4 + BNE R4, _subloop2 + + /* sum[alen] = carry */ +_subend: + RET |