Parallelize clang-tidy runs

[abadams]

Using a script provided by llvm. This makes it way faster to clang-tidy a branch before opening a PR.

[steven-johnson]

On my Mac, make clang-tidy-fix fails with /Users/srj/llvm-trunk-install/bin/../share/clang/run-clang-tidy.py: No such file or directory

[abadams]

Does /Users/srj/llvm-trunk-install/bin/clang-tidy exist for you? On top of the instructions in the readme I think you need to do a make install and enable the clang-tools-extra project.

[steven-johnson]

Does /Users/srj/llvm-trunk-install/bin/clang-tidy exist for you? On top of the instructions in the readme I think you need to do a make install and enable the clang-tools-extra project.

Nope. We should add that to the README.

[abadams]

Done.

[steven-johnson]

After doing that, I now can run it on OSX, but it is unable to find ~any of the system , e.g. /Users/srj/GitHub/Halide/src/IR.h:8:10: error: 'string' file not found [clang-diagnostic-error] #include <string>

[steven-johnson]

I also get a number of warnings of the form

/Users/srj/GitHub/Halide/src/IR.h:666:68: error: the parameter 'param' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param,-warnings-as-errors]
    static Expr make(Type type, const std::string &name, Parameter param) {

[abadams]

Can you try adding libcxx;libcxxabi to the list of enabled projects? For this to work you need to be able to actually compile c++ with the llvm that you built.

Those warnings sound like things that should be fixed. Not sure why I don't get them with my clang-tidy.

[steven-johnson]

libcxx;libcxxabi

Trying now, but FWIW, that adds a lot to the build (> 1000 files).

Since clang-tidy might be available in prebuilt form, it might be worth smartening our script to do something like:
(1) if $CLANG_TIDY is defined, use that
(2) else, if which clang-tidy reports it is available, use that
(3) else, use the logic based on $LLVM_CONFIG that we do now

(AFAICT, Homebrew doesn't offer a clang-tidy formula on Mac, but the prebuilts you can download include it)

[abadams]

I think the Makefile is already smart in that way. For any complete llvm install, prebuilt or not, setting LLVM_CONFIG correctly will find the rest of it. It sounds like to run clang-tidy you need a more complete llvm install than you currently have? Or maybe the homebrew prebuilt is only a partial build of llvm?

The default value of RUN_CLANG_TIDY points to llvm's standard install location for run-clang-tidy.py using the location of CLANG, which comes from querying llvm-config where to look.

[steven-johnson]

I think the Makefile is already smart in that way. For any complete llvm install, prebuilt or not, setting LLVM_CONFIG correctly will find the rest of it. It sounds like to run clang-tidy you need a more complete llvm install than you currently have? Or maybe the homebrew prebuilt is only a partial build of llvm?

The default value of RUN_CLANG_TIDY points to llvm's standard install location for run-clang-tidy.py using the location of CLANG, which comes from querying llvm-config where to look.

I'm building from scratch, with LLVM_ENABLE_PROJECTS="clang;lld;clang-tools-extra" (still rebuilding the libcxx stuff)

[steven-johnson]

(FWIW: I never bothered trying make clang-tidy locally before now anyway, so it was likely broken already, and I will probably rely on the presubmit checks anyway most of the time. That said, might as well figure out the failure modes while we are here.)

[abadams]

Yeah, I'm assuming this PR doesn't actually change the requirements for you. If run-clang-tidy.py doesn't work then probably clang-tidy didn't either.

[steven-johnson]

FYI: after rebuilding llvm with the libcxx;libcxxabi projects enabled, make clang-tidy is unchanged for me on this branch (still can't find system headers).

FYI #2: on the master branch, make clang-tidy just fails outright for me like so:

echo '[' >> bin/build/compile_commands.json
bash: bin/build/compile_commands.json: No such file or directory
make: *** [bin/build/compile_commands.json] Error 1

so, I guess this is a net improvement? Something is wonky but fine with me to land if you like.

[abadams]

master is missing a key mkdir. It would be interesting to know if clang-tidy works if you manually create bin/build first.

[steven-johnson]

(OK to land this without the buildbot testing IMHO)