4 ms·
Wouldn't this be the ideal instruction for implementing multi-word arithmetic? If the carry flag is set from the previous (lower order) addition, increase the
by mpweiher 3y ago
Wouldn't this be the ideal instruction for implementing multi-word arithmetic? If the carry flag is set from the previous (lower order) addition, increase the next word up by one and continue adding.
And of course ARM 32 had conditional execution for all instructions. These appear the variants that were useful enough to keep around when the general feature was removed from aarch64
- gpvos 3y agoARM has both add-with-carry and add-without-carry instructions, a separate increment is not necessary. (I don't know much about AArch64, only ancient ARM2/3, but I expect they left this in).
- Findecanor 3y agoYes AArch64 has "adds" for modifying the carry flag after the first addition and then "adcs" for using and modifying the carry flag in subsequent additions.
- wbl 3y agoARM used to have the beautiful UMALL, a single instruction that would multiply two registers then accumulate two other values into the result, then store as a double word into the registers. This is the inner loop of multiplication and was very nice to use, but died in the AArch64 transition.