Drop LLVM 3.5 and LLVM 3.6 support

[ysbaddaden]

Since omnibus will be updated to use LLVM 3.8.1, this drops support for older, buggy, LLVM releases. This also cleans up the codebase.

The supported LLVM versions are now 3.8, 3.9 and 4.0 (manually tested).

[bcardiff]

Note: We are missing invocations to llvm-config-4.0, in some linux packages there might be no llvm-config but llvm-config-4.0. (in the Makefile and lib_llvm.cr). I was expecting to do that soon, but it will conflict slightly with this.

This can't be merged until the omnibus-crystal is migrated to use newer llvm, so avoid merging until @matiasgarciaisaia or @waj says so.

[dmitryrck]

How about Dockerfile? It is using 3.5.0.

%  docker run --rm crystallang/crystal crystal --version
Crystal 0.22.0 [3c71228] (2017-04-20) LLVM 3.5.0

P. S.: I mean not necessarily updating it in this PR, but it is required to update 😉 .

[ysbaddaden]

The docker image is based on released Crystal AFAIK so it should be updated on next release.

I initially didn't had llvm-config-4.0 when I merged the compatibility commits, because LLVM4 was in beta. We can decide to upgrade to LLVM4 by default (or as a fallback) now that it's stable. Your call, I'll make the change.

[dmitryrck]

Great! :D

[akzhan]

I suppose that latest stable LLVM should be default one.

[ysbaddaden]

LLVM 3.9 is the current stable. LLVM 4 is qualification and LLVM 5 is unstable. Some package managers (i.e. homebrew) are pushing the qualification release as stable but it's actually not by LLVM terms.

[akzhan]

Looks like these functions should be uncommented.

https://github.com/crystal-lang/crystal/blob/master/src/math/libm.cr#L6

[Sija]

Also:

• https://github.com/crystal-lang/crystal/blob/master/src/math/libm.cr#L34
• https://github.com/crystal-lang/crystal/blob/master/src/math/math.cr#L112
• https://github.com/crystal-lang/crystal/blob/master/src/math/math.cr#L134

[ysbaddaden]

1. this PR drops support for older LLVM releases (cleanup);
2. that depends on which LLVM release the intrinsics were introduced (it's unclear).

[akzhan]

@ysbaddaden As @RX14 said - minnum and maxnum were introduced in LLVM 3.6.

[ysbaddaden]

Bump. Since omnibus now relies on LLVM 3.8 can we drop support for older, buggy, LLVM versions?

[sdogruyol]

Bump 👍

[matiasgarciaisaia]

I'm not that sure it's wise to merge this until we get rid of things like #4719 I'd treat 3.8 builds as release candidates for now - I'd rather have the safety net of falling back to 3.5 if anything gets to ugly. Probably over-conservative, but that's what I feel. I'm open to other opinions, anyway.

[akzhan]

Everywhere in code I see mentions about ugly earliest LLVM < 3.9.

We must drop support for old LLVMs because of

1. LLVM LexicalScopes build exception when building with --release flag #4719 (comment)
2. Crystal still in early development stages, so support for old codebase is not needed.

[RX14]

The solution is to statically compile LLVM into the crystal compiler so we can support 1 or maybe 2 LLVM major versions and not have to worry about distributions.

[ysbaddaden]

Closing, this was merged in #4821.