base:advanced_optimizing
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base:advanced_optimizing [2021-01-20 10:15] bitbreaker [Forming terms] |
base:advanced_optimizing [2021-03-05 16:57] (current) bitbreaker [Forming terms] |
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| sbc num | sbc num | ||
| sta neg | sta neg | ||
| + | | ||
| + | ;num in a, carry set | ||
| + | lda num | ||
| + | sbc #$01 | ||
| + | eor #$ff | ||
| </ | </ | ||
| - | There are of course also other expressions possible, just ponder a while about the term. | + | There are of course also other expressions possible, just ponder a while about the term. Also the carry flag after the negation can be influenced, depending on using sbc or adc for most cases ($00/$ff will cause an overflow). |
| How's about forming terms with logical operations? We notice, that for e.g. (a + b) xor $ff is the same as (a xor $ff) - b: | How's about forming terms with logical operations? We notice, that for e.g. (a + b) xor $ff is the same as (a xor $ff) - b: | ||
base/advanced_optimizing.txt ยท Last modified: 2021-03-05 16:57 by bitbreaker