[llvm] [IR] Add a test for `f128` libm libcall lowering (NFC) (PR #148308)

[Nikita Popov via llvm-commits]

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@@ -0,0 +1,337 @@
+; Verify that fp128 intrinsics only lower to `long double` calls (e.g. sinl) on
+; platforms where 128 and `long double` have the same layout.Otherwise, lower
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nikic wrote:

```suggestion
; platforms where 128 and `long double` have the same layout. Otherwise, lower
```

https://github.com/llvm/llvm-project/pull/148308