Blockers for Clang support on all supported platforms

[psmarshall]

I'd like to discuss what the support for compiling with Clang is like on all supported platforms. The context is that the V8 team is thinking about experimenting with Clang plugins that will automatically generate stack maps. This means V8 C++ code could store tagged pointers to heap values directly on the stack, rather than indirectly through Handles.

Particularly I don't know what the support is like on AIX, FreeBSD etc.

Adding folks who might be interested.. @mhdawson @hannespayer @mlippautz @hashseed

[richardlau]

cc @nodejs/platforms

[mhdawson]

@ThePrez can you check out and answer for IBM i
@john-yan @miladfarca can you track down the answer for AIX
@john-yan, @miladfarca can you also answer for Linux on P, Linux on Z
@john-yan, @miladfarca can you follow up with Igor (could not find his github id just yet) on z/OS

[john-yan]

@mhdawson from what I know, clang/llvm doesn't support AIX. Linux on P/Z should be workable.
@joransiu Can you check with Igor on z/OS?

[miladfarca]

Work might be underway for supporting clang on AIX but not supported at the moment: http://lists.llvm.org/pipermail/llvm-dev/2019-February/130175.html

[joransiu]

@psmarshall : Just wanted to make sure I understand the proposed plugin here: Are we generating stack maps for select locations within V8 C++ functions, to map the frame slots that contain tagged pointers to heap?

Do you have details on which specific clang plugin APIs will be used?

[refack]

/CC @nodejs/platform-smartos

There's also the @nodejs/build resource bottleneck 🤷‍♂️

Windows issue:
Refs: #19630

General BuildWG discussion:
Refs: nodejs/build#1543

P.S. We currently already do CI/CD on freeBSD with CLang

P.P.S. We need a cross-compiler toolchain for building ARM binaries nodejs/build#1238

[bnoordhuis]

can you follow up with Igor (could not find his github id just yet) on z/OS

@IgorTodorovskiIBM?

[IgorTodorovskiIBM]

Node on z/OS ships with the IBM njsc compiler (which is based on clang). However, there are currently a few issues with respect to creating clang plugins that are being investigated.

[hashseed]

There is no Clang plugin yet, but we will likely experiment on this front soon.

[jasnell]

@nodejs/build ... does this need to remain open?

[mhdawson]

@psmarshall any updates on this front?

[psmarshall]

The current plan is to explore conservative stack scanning which doesn't rely on a clang plugin so this isn't relevant anymore. Thanks!