ChatGPT powerpc instruction question

Perfect — let’s build two separate lists of PowerPC instructions that

do not alter registers, and

either (A) allow traps or (B) exclude traps as control flow changes.



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📑 List A — Registers not altered, traps allowed

(These don’t write back into registers. They may affect memory, caches, ordering, or trigger a trap, but that’s okay under this definition.)

Synchronization

sync        (31 / XO=598)
eieio       (31 / XO=854)
isync       (19 / XO=150)

Data Cache Block Ops

dcbf        (31 / XO=86)
dcbst       (31 / XO=54)
dcbi        (31 / XO=470)
dcbt        (31 / XO=278)
dcbtst      (31 / XO=246)
dcbz        (31 / XO=1014)

Instruction Cache

icbi        (31 / XO=982)

TLB Ops

tlbie       (31 / XO=306)
tlbia       (31 / XO=370)   [optional/implementation-specific]

Trap Instructions (no register writes, but may raise exception)

tdi         (2)
td          (31 / XO=68)    Trap Doubleword (register form)
tw          (31 / XO=4)     Trap Word
twi         (3)             Trap Word Immediate


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📑 List B — Registers not altered, no control flow change at all

(This is the strict interpretation: no register writes and no possible PC change, even via exception/trap.)

Synchronization

sync        (31 / XO=598)
eieio       (31 / XO=854)
isync       (19 / XO=150)

Data Cache Block Ops

dcbf        (31 / XO=86)
dcbst       (31 / XO=54)
dcbi        (31 / XO=470)
dcbt        (31 / XO=278)
dcbtst      (31 / XO=246)
dcbz        (31 / XO=1014)

Instruction Cache

icbi        (31 / XO=982)

TLB Ops

tlbie       (31 / XO=306)
tlbia       (31 / XO=370)   [optional/implementation-specific]


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✅ So the difference is that List A includes td, tdi, tw, twi, while List B excludes them because they can change control flow by causing exceptions.