2 ms·
> "always" is not the weird one -- that's just the same as everyone else. "Never" is weird, immediately spending 1/16th of the opcode space (256 million instruc
by naniwaduni 5y ago
> "always" is not the weird one -- that's just the same as everyone else. "Never" is weird, immediately spending 1/16th of the opcode space (256 million instructions) on NO-OPs.
Worse, iirc what looks like it should be the slot for the "never" condition actually does exactly the same thing as "always".
- brucehoult 5y agoHmm. I guess I never actually tried it. The A64 manual says 1111 on a Bcc etc disassembles as NV but does the same as AL. The ARM7TDMI manual says 1111 is reserved and don't use it. I don't know the actual behaviour. Aha. The Welsh&Knaggs "ARM Book" says before ARMv3 NV meant NV. In ARMv3 and ARMv4 NV is unpredictable. And in ARMv5 NV is used to encode "various additional instructions that can only be executed unconditionally".