Instruction sets

[tdesveauxPKFX]

Currently, vectorextensions can only hold one value at a time which make sense as avx include sse and avx2 include avx and so on.

But in gcc 5.4, if you want both avx2 and f16c you need -mavx2 and -mf16c and -mf16c does not include avx2.
Another example, -mbmi2 does not include -mbmi.

I am wondering what is the best way too add this in premake, a new api entry or setting vectorextensions kind to a list:string.

I personally am leaning toward a new api but wanted your input on this.

Note that visual studio manage this internally, f16c is used since visual 2012 so this option is for gcc and clang.

[samsinsane]

Making vectorextensions a list:string would be fine, I'm not sure why a new API would be required, but if you have good enough reasons that should be fine, or if others have strong reasons for it to be that way.

As I have no knowledge on these, does it make sense to specify some of these options without the others? For example, avx2 without f16c or vice versa? If it doesn't, perhaps you could just additionally emit these compiler switches with -mavx2, et al?

[tdesveauxPKFX]

My main reason toward creating a new api is that visual studio has a vector extension property (Enable Enhanced Instruction Set) that is covered by the vectorextensions api. VS take only one value for this property but gcc and clang can take multiple "-m" options. This is why I feel that we should keep vectorextensions as is.

I have two other smaller reasons for this.
Keep in mind that I do not have that much knowledge about these concepts so if someone feel the need to correct me, please do.
As I understand it, we can say that SSE, AVX and F16C are vector extension but not BMI so a new api is more about terminology and self documentation (something like instruction sets extensions, quite a mouthful). (One of my colleague is on the fence with F16C as it does use vector registers but it is misleading https://en.wikipedia.org/wiki/F16C#Technical_information).

Finally, I did not encounter this issue and it might never be one but if someone want to do something like

project "prj"
    ...
    vectorextensions "avx2"

    filter{ "files:src.cpp" }
        vectorextensions "sse"

With vector extension being a list:string, the gcc command line for src.cpp would be
gcc -mavx2 -msse ...
which is not what I would expect seeing the lua file.

About AVX2 and F16C, VS does use F16C everywhere but gcc let the user choose to use F16C alone or not so I feel we should follow gcc here.
Also, AVX and F16C have two different goals. It would make little sense to me to add F16C to AVX.

[samsinsane]

I see what you're saying, I agree with you regarding the new API. isaextensions might be a good name instead of instructionsetextensions or instructionsetarchitectureextensions.

[tdesveauxPKFX]

Good, something else took priority over this but I hope to do this before this week's end.

I might have other questions like this in the future, are github issues the correct way to do this or would you prefer I use the google developer group?

[starkos]

The developer group is generally pretty quite; GitHub issues are proving to be more useful.

[samsinsane]

Closing this as the PR was merged.