diff options
Diffstat (limited to 'libmp/Plan9-power/mpvecsub.s')
| -rw-r--r-- | libmp/Plan9-power/mpvecsub.s | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/libmp/Plan9-power/mpvecsub.s b/libmp/Plan9-power/mpvecsub.s new file mode 100644 index 00000000..c2a05bc1 --- /dev/null +++ b/libmp/Plan9-power/mpvecsub.s @@ -0,0 +1,57 @@ +#define BDNZ BC 16,0, +#define BDNE BC 0,2, + +/* + * mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff) + * + * diff[0:alen-1] = a[0:alen-1] - b[0:blen-1] + * + * prereq: alen >= blen, diff has room for alen digits + * + * R3 == a + * R4 == alen + * R5 == b + * R6 == blen + * R7 == diff + * R8 == temporary + * R9 == temporary + */ +TEXT mpvecsub(SB),$-4 + + MOVW alen+4(FP),R4 + MOVW b+8(FP),R5 + MOVW blen+12(FP),R6 + MOVW diff+16(FP),R7 + SUB R6, R4 /* calculate counter for second loop (alen > blen) */ + SUB $4, R3 /* pre decrement for MOVWU's */ + SUB $4, R5 /* pre decrement for MOVWU's */ + SUBC $4, R7 /* pre decrement for MOVWU's and set carry */ + + /* skip subraction if b is zero */ + CMP R0,R6 + BEQ _sub1 + + /* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */ + MOVW R6, CTR +_subloop1: + MOVWU 4(R3), R8 + MOVWU 4(R5), R9 + SUBE R9, R8, R8 + MOVWU R8, 4(R7) + BDNZ _subloop1 + +_sub1: + /* skip subtraction if a is zero */ + CMP R0, R4 + BEQ _subend + + /* diff[blen:alen-1] = a[blen:alen-1] - 0 + carry */ + MOVW R4, CTR +_subloop2: + MOVWU 4(R3), R8 + SUBE R0, R8 + MOVWU R8, 4(R7) + BDNZ _subloop2 +_subend: + RETURN + |