diff options
Diffstat (limited to 'libmp/Plan9-amd64/mpvecsub.s')
| -rw-r--r-- | libmp/Plan9-amd64/mpvecsub.s | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/libmp/Plan9-amd64/mpvecsub.s b/libmp/Plan9-amd64/mpvecsub.s new file mode 100644 index 00000000..9e1b5349 --- /dev/null +++ b/libmp/Plan9-amd64/mpvecsub.s @@ -0,0 +1,45 @@ +/* + * 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 + */ +TEXT mpvecsub(SB),$0 + +/* MOVQ a+0(FP),SI */ + MOVQ RARG, SI + MOVQ b+16(FP),BX + MOVL alen+8(FP),DX + MOVL blen+24(FP),CX + MOVQ diff+32(FP),DI + SUBL CX,DX + XORL BP,BP /* this also sets carry to 0 */ + + /* skip subraction if b is zero */ + TESTL CX,CX + JZ _sub1 + + /* diff[0:blen-1],borrow = a[0:blen-1] - b[0:blen-1] */ +_subloop1: + MOVL (SI)(BP*4),AX + SBBL (BX)(BP*4),AX + MOVL AX,(DI)(BP*4) + INCL BP + LOOP _subloop1 + +_sub1: + INCL DX + MOVL DX,CX + LOOP _subloop2 + RET + + /* diff[blen:alen-1] = a[blen:alen-1] - 0 */ +_subloop2: + MOVL (SI)(BP*4),AX + SBBL $0,AX + MOVL AX,(DI)(BP*4) + INCL BP + LOOP _subloop2 + RET + |