base:advanced_optimizing
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| Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
| base:advanced_optimizing [2021-01-20 10:15] – [Forming terms] bitbreaker | base:advanced_optimizing [2021-04-19 08:26] – [LAX] bitbreaker | ||
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| Actually you can use LAX also with an immediate value, but it behaves a bit unstable regarding the given immediate value. However when simply doing an LAX #$00 you are fine. | Actually you can use LAX also with an immediate value, but it behaves a bit unstable regarding the given immediate value. However when simply doing an LAX #$00 you are fine. | ||
| + | |||
| + | lda $xxxx,y is not available as 8 bit version, so an lda $xx,y is not possible. With lax $xx,y there is howeever a way to imitate a lda $xx,y at the cost of destroying x. | ||
| ===== SAX/SHA ===== | ===== SAX/SHA ===== | ||
| Line 1430: | Line 1432: | ||
| 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 · Last modified: 2024-03-03 11:06 by bitbreaker