[clang] [clang]Implement the c23 stdc bit builtins (PR #185978)

[Eli Friedman via cfe-commits]

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@@ -0,0 +1,19 @@
+#ifndef LLVM_CLANG_TEST_STDBIT_H
+#define LLVM_CLANG_TEST_STDBIT_H
+
+#define stdc_leading_zeros(x) (__builtin_stdc_leading_zeros((x)))
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efriedma-quic wrote:

Right, the C library only needs an external identifier for the versions with suffixes (stdc_leading_zeros_ull etc.).  Which doesn't require anything fancy.

https://github.com/llvm/llvm-project/pull/185978