[llvm-dev] Multiple documents in one test file

[Chen, Yuanfang via llvm-dev]

Interesting. `-split-input-file` is indeed terse and performant for tests with similar run lines. To generalize the functionality a bit, I'm not sure if people have had the idea of let LIT to the splitting using some common separator lines like `# SEP: #`, `// SEP: //` etc.

________________________________________
From: Mehdi AMINI <joker.eph at gmail.com>
Sent: Monday, July 13, 2020 8:06 PM
To: Chen, Yuanfang
Cc: llvm-dev; Fangrui Song
Subject: Re: [llvm-dev] Multiple documents in one test file

We have a similar option (-split-input-file) in `mlir-opt`: https://github.com/llvm/llvm-project/blob/master/mlir/test/Dialect/Affine/invalid.mlir

With a single `RUN:` lit invocation the tool itself will loop over all the split sections in the file. This is convenient to test error cases where the tool would abort at the first error otherwise. I don't think we can easily achieve this with a single pipe and a separate `extract` command though?

--
Mehdi



On Mon, Jul 13, 2020 at 6:43 PM Chen, Yuanfang via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
`extract` +1 for consistency.

________________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org<mailto:llvm-dev-bounces at lists.llvm.org>> on behalf of Fangrui Song via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
Sent: Monday, July 13, 2020 6:17 PM
To: llvm-dev
Subject: [llvm-dev] Multiple documents in one test file

Sometimes it is convenient if we can specify multiple independent tests
in one file. To give an example, let's discuss test/MC/ELF/debug-md5.s and
test/MC/ELF/debug-md5-err.s (.file directive in the assembler).

a) An invalid .file makes the whole file invalid. Because errors lead to a
non-zero exit code, We have to use `RUN: not llvm-mc %s` for the whole file.
This often lead to users placing good (`RUN: llvm-mc %s`) and bad tests (`RUN:
not llvm-mc %s`) separately. For some features, having both good and bad tests
in one file may improve readability.
b) .debug_line is a global resource. Whenever we add a (valid) .file, we
contribute an entry to the global resource. If we want to test some
characteristics when include_directories[0] is A, and other characteristics
when include_directories[0] is B, we have to use another test file.

The arguments apply to many other types of tests (opt on .ll, llc on .ll and .mir, clang on .c, yaml2obj on .yaml, etc).

I have a patch teaching llvm-mc about an option to split input: https://reviews.llvm.org/D83725
(30+ lines)

In a comment, Richard Smith mentioned whether we can add a separate extractor utility:

```
# RUN: extract bb %s | llvm-mc - 2>&1 | FileCheck %s --check-prefix=BB

or

# RUN: extract bb %s -o %t.bb<http://t.bb>
# RUN: llvm-mc %t.bb<http://t.bb> 2>&1 | FileCheck %t.bb<http://t.bb>
```

The advantage is its versatility. The downside is somewhat verbose syntax.


Some questoms:

1. What do people think of the two approaches? An in-utility option vs a standalone utility.
2. For llvm-mc, if we go with an option, is there a better name than --doc-id? David Blaikie proposed --asm-id
   (This is my personal preference, trading 30+ lines in a utility for simpler syntax)
3. If we add a standalone utility, how shall we name it? (Note that llvm-extract exists, but people can probably distinguish 'extract' from llvm-extract
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