[fpc-devel] LEA instruction speed

J. Gareth Moreton gareth at moreton-family.com
Tue Oct 3 09:41:48 CEST 2023


What should I call a new sub-CPU option?  Should it be "ICELAKE" or is 
there a better name like "CORE10" or "COREX" (X being the Roman numeral 
for 10, standing in for the 10th generation of Intel Core)?

Kit

On 03/10/2023 08:02, Florian Klämpfl via fpc-devel wrote:
>
>> Am 03.10.2023 um 03:32 schrieb J. Gareth Moreton via fpc-devel <fpc-devel at lists.freepascal.org>:
>>
>> Hi everyone,
>>
>> This is mainly to Florian, but also to anyone else who can answer the question - at which point did a complex LEA instruction (using all three input operands and some other specific circumstances) get slow?
> Maybe check Agner’s list?
>
>> Preliminary research suggests the 486 was when it gained extra latency, and then Sandy Bridge when it got particularly bad.  Icy Lake seems to be the architecture where faster LEA instructions are reintroduced, but I'm not sure about AMD processors.
>>
>> Should I introduce a new x86 subprocessor named "ICYLAKE" or is there a better name or does it fall under one of our categories already (CORE_AVX2 or ZEN3)?
> If it doesn’t fit in the existing ones, you can always add new ones
>
>> Kit
>>
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