[llvm] [update_test_checks] Generate multiple SAME lines to avoid back-reference issues. (PR #172452)

[Nikita Popov via llvm-commits]

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@@ -24,7 +24,7 @@
 2: --function-signature is now enabled by default and also checks return
    type/attributes.
 3: Opening parenthesis of function args is kept on the first LABEL line
-   in case arguments are split to a separate SAME line.
+   in case arguments are split to separate SAME lines.
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nikic wrote:

Oh, I see, the problem is a backreference after a long list of unrelated capture groups.

I feel like UTC is not really the right place to address this. This splitting seems like something FileCheck could do internally. Though possibly the easiest thing to do would be to add support for more than 9 backreferences to the regex engine (I think this would require a small change to regcomp.c only).

https://github.com/llvm/llvm-project/pull/172452