Post #2409997
2025-09-09 04:13 UTC
@rygorous@mastodon.gamedev.place @regehr@mastodon.social @steve@discuss.systems The one actual "killer" feature of the x86 ISA was load-op. It turns out that a LOT of instructions want to load a value from memory, do an operation on it, and never reference that value again.
Most RISC ISAs make you send that value through a register, which is precious rename/read/write/etc bandwidth.
But, offset that against the more complex encoding of load-op. Which one wins is very context-specific, and it doesn't win by that much.
Replies (1)
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@TomF@mastodon.gamedev.place 2025-09-09 04:15
@rygorous@mastodon.gamedev.place @regehr@mastodon.social @steve@discuss.systems But for sure, when I retire and make the finest ISA in the world, it will have load-op in some form or other. Because it's a good idea and saves a lot of power. (the OOO engines all spot this use pattern by the way, so they also save the power, but it's indirect)