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changeset 102:baead5689afc
Fix logic errors in floating point addition routine
| author | William Astle <lost@l-w.ca> |
|---|---|
| date | Mon, 30 Oct 2023 20:48:29 -0600 |
| parents | b0422868a7b1 |
| children | 2f97bfecffab |
| files | src/fps.s |
| diffstat | 1 files changed, 5 insertions(+), 4 deletions(-) [+] |
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--- a/src/fps.s Mon Oct 23 23:15:55 2023 -0600 +++ b/src/fps.s Mon Oct 30 20:48:29 2023 -0600 @@ -121,7 +121,8 @@ std fpa1+fpa.sig+5 std fpa1+fpa.sig+7 sta fpa1+fpa.sig+9 - subb fpa0+fpa.exp ; calculate exponent difference + ldb fpa0+fpa.exp ; fetch exponent of second argument + subb fpa1+fpa.exp ; calculate exponent difference lbeq fps_add8 ; brif same exponent - no need to denormalize bcs fps_add4 ; brif second operand is bigger ldx #fpa1 ; point to second operand to denormalize @@ -129,11 +130,11 @@ bhs fps_add0 ; brif so - return first operand bra fps_add5 ; go shift operand right by B places fps_add4 negb ; get positive number of shifts + cmpb #10 ; shifting more than precision? + bhs fps_add2 ; brif so - return second operand ldx #fpa0 ; shift left operand right B places lda fpa1+fpa.exp ; set exponent of result to larger of two sta fpa0+fpa.exp - cmpb #10 ; shifting more than precision? - bhs fps_add2 ; brif so - return second operand fps_add5 subb #2 ; do we need at least two places? bcs fps_add6 ; brif not lda fpa.sig+8,x ; shift right into extra digits @@ -220,7 +221,7 @@ cmpa fpa1+fpa.sig+4 bne fps_add9 lda fpa0+fpa.sig+5 - cmpa fpa1+fpa.sig+5 ; don't have to check other extras; only one set will be set + cmpa fpa1+fpa.sig+5 ; don't have to check other extras; the first extra will be decisive fps_add9 bhs fps_add10 ; brif first operand is bigger ldx #fpa0 ; point to first operand as smaller lda fpa1+fpa.sign ; set result sign to that of larger operand