[PATCH] D55572: [AArch64] Add patterns for zext/sext of shift amount.

[Tim Northover via Phabricator via llvm-commits]

t.p.northover added a comment.

> update_llc_test_checks is a useful starting point because it generates the right checks to ensure you're checking the whole function, which is inconvenient to do by hand (trying to CHECK-NOT your way to checking the whole function is a bad idea).

I can see some benefit there, though when the tests do break I'm often annoyed by it checking irrelevant details (those comments in this case, for example). Either way I think we should very strongly discourage people from treating its output as good enough for final tests except in trivial one-instruction cases.

> I can replace the explicit reference to r8 with a regex, sure.

Thanks.

> (We could look at modifying update_llc_test_checks to generate a regex where appropriate, I guess... but it might be tricky to distinguish when a value is ABI-significant.)

I was musing along similar lines myself this morning. Intel vs AT&T (and use/def in general) would also be tricky; I suspect it would need to bake quite a bit of target-specific knowledge into it to get reasonable output.


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  rL LLVM

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https://reviews.llvm.org/D55572