[fpc-devel] LEA instruction speed

[Tomas Hajny]

On October 3, 2023 03:32:34 +0200, "J. Gareth Moreton via fpc-devel" <fpc-devel at lists.freepascal.org> wrote:


Hii Kit,

>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?  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.

I cannot answer your question, but if you prepare a test program, I can run it on an Intel 486 DX2 100 Mhz and AMD Athlon 1 GHz machines if it helps you in any way (at least I hope the 486 DX2 machine should be still able to start ;-) ).

Tomas