[clang] [clang] constexpr `__builtin_elementwise_abs` support (PR #152497)

[Iris Shi via cfe-commits]

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@@ -115,6 +115,8 @@ Non-comprehensive list of changes in this release
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 - Added ``__builtin_elementwise_fshl`` and ``__builtin_elementwise_fshr``.
 
+- Added `__builtin_elementwise_abs`.
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el-ev wrote:

It's not "Added", it's making the function constexpr.

https://github.com/llvm/llvm-project/pull/152497