llvmGen: Adapt to allow LLVM 15

We now must use -passes in place of -O<n> due to #21936 (closed).

Closes #21936 (closed). Closes #22220 (closed).

I assume -passes is backwards compatibles up to llvm 10?

requested review from @AndreasK

We probably also want to backport this to 9.4

added backport needed:9.4 label

Is this actually correct as is? Last week I tried passing "-passes=default1,-globalopt" to llvm and iirc it complained about one either having to pass the defaults or a list of flags.

marked this merge request as draft

mentioned in merge request !9145 (closed)

added 1 commit

• baa77724 - Update llvm-passes

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While -passes is supported by LLVM 10, the default1 convention appears not to be supported by 10, 11, or 14. In fact, I'm beginning to wonder whether it's even supported at by 15.

Also relevant: https://llvm.org/docs/NewPassManager.html.

For the record, the best way I have found to dumping the passes run by clang is https://groups.google.com/g/llvm-dev/c/p7KYRoA8AHY?pli=1

added 140 commits

• baa77724...1ebd521f - 139 commits from branch master
• bb6bb0f7 - llvmGen: Adapt to allow LLVM 15

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The problem here, as noted by @duog, is the -tbaa flag which is a pass.

mentioned in merge request !9287 (closed)

added 332 commits

• bb6bb0f7...3d55d8ab - 331 commits from branch master
• 30694951 - llvmGen: Adapt to allow LLVM 15

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changed the description

It seems with LLVM 15.0.6 here, opt-15 doesn't work with -passes=tbaa at all:

opt-15: unknown pass name 'tbaa'

mentioned in issue #12798

@bgamari @mpickering I understand this has been superseded by matts work?

To some extent, yes. Ultimately we will soon need to switch to the new pass manager, which will require that we revisit this MR.

mentioned in issue #22954 (closed)

removed review request for @AndreasK