[llvm-dev] New x86-64 micro-architecture levels (original) (raw)

Allan Sandfeld Jensen via llvm-dev llvm-dev at lists.llvm.org
Sat Jul 11 00:40:06 PDT 2020

On Freitag, 10. Juli 2020 19:30:09 CEST Florian Weimer via Gcc wrote:

glibc (or an alternative loader implementation) would search for libraries starting at level D, going back to level A, and finally the baseline implementation in the default library location.

I expect that some distributions will also use these levels to set a baseline for the entire distribution (i.e., everything would be built to level A or maybe even level C), and these libraries would then be installed in the default location. I'll be glad if I can get any feedback on this proposal. I plan to turn it into a merge request for the x86-64 psABI document eventually. Sounds good, though if I could dream I would also love a partial replacement option. So that you could have a generic x86-64 binary that only had some AVX2 optimized replacement functions in a supplementary library.

Perhaps implemented by marked the library as a partial replacement, so the dynamic linker would also load the base or lower libraries except for functions already resolved.

You could also add a level E for the AVX512 instructions in ice lake and above. The VBMI1/2 instructions would likely be useful for autovectorization in GCC.

'Allan

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