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>early processors Early processors had speculative execution? I thought this had been added to Intel/AMD/ARM about 20 years ago?
by FLUX-YOU 9y ago
>early processors
Early processors had speculative execution? I thought this had been added to Intel/AMD/ARM about 20 years ago?
- DiThi 9y agoI think it means they're tricks for better performance when you _don't_ have speculative execution.
- dzdt 9y agoI guess he means the retpoline. On the 6502 there is no indirect jump instruction, so you need such tricks just to achieve an indirect jump at all.
- pubby 9y agoThere's an indirect jump instruction. It's not very good though, and has a notorious bug with addresses ending in 0xFF.
- dzdt 9y agoGah, you're right. Guess my memory is fading. There is indirect JMP, but no indirect JSR or indirect branches. And the indirect JMP as you say is not very useful.
- gpderetta 9y agoSpeculative execution is as old as branch prediction, which is very, very old.