[llvm] [LV] Teach the loop vectorizer llvm.sincos is trivially vectorizable (PR #128035)

[David Sherwood via llvm-commits]

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david-arm wrote:

I know we don't have masked variants of sincos available, but is it still useful to have a test for a predicated loop with sincos to make sure the cost looks sensible?

https://github.com/llvm/llvm-project/pull/128035