[PATCH] D83725: [llvm-mc] Add --doc-id=<id> to support multiple documents in a file

Mon Jul 13 16:42:59 PDT 2020

MaskRay added a comment.

In D83725#2148760 <https://reviews.llvm.org/D83725#2148760>, @dblaikie wrote:

> > yaml2doc supports --docnum=<num> to allow multiple documents in a file. Combing tests prudently can improve readability. This patch adds a similar --doc-id=<id> to llvm-mc.
>
> Presumably "doc" makes sense in the yaml2doc context - perhaps "obj" would make more sense in llvm-mc
>
> But I'm not sure it's the best direction - we have lots of input files (testing IR, testing C++, etc) where we don't have this ability to have multiple distinct inputs in one file & it seems to work OK? Is there something different about llvm-mc that motivates this feature here especially?

If we want to test local things (how IR is lowered, how instructions are assembled, how bytes are disassembled), whatever the containing function is named does not matter. Say, we have a function `foo`, and we want to test a variant of it, we can just add another function `bar`, duplicating the content in `foo` and adding some variance.

However, this works poorly for some "global resources". For example, if we want to test the content of .strtab, the order of section headers, etc. We can't say: the first 3 input lines test the case of 3 symbols, the last 4 input lines test the case with 4 symbols - .symtab is a singleton, if you want to test 4 symbols, the 3 symbol case is not tested any more.

What we currently do is to add another test file, with some variation to the first test file. It is not rare for me to diff two test files and find the differences. It'd be easier if two similar things are tested in one file, with a comment explaining the differences.

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https://reviews.llvm.org/D83725