On 2022-09-07 16:34, J. Gareth Moreton via fpc-devel wrote:
So this one has eluded me a little bit... what's the exact difference between the -Cp and -Op options?
-Cp: the code is only guaranteed to run on this cpu and usually also later ones (the code generator/optimiser can use instruction that are not available on earlier/other cpus). E.g.: use BMI2 instructions. -Op: the code is optimised for this cpu, but will still run on earlier/later ones. E.g., use lea instead of shl on a particular cpu because it's faster there, even if it's not the case on all of them. -Cf: use this instruction set to perform floating point calculations. It is independently handled from the two previous settings, even if it can indirectly also influence the minimum required CPU.
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