[clang] [flang] [Flang][AArch64][VecLib] Add libmvec support for Flang/AArch64 (PR #146453)

[Paul Walker via cfe-commits]

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@@ -3487,7 +3487,8 @@ def fno_experimental_isel : Flag<["-"], "fno-experimental-isel">, Group<f_clang_
   Alias<fno_global_isel>;
 def fveclib : Joined<["-"], "fveclib=">, Group<f_Group>,
   Visibility<[ClangOption, CC1Option, FlangOption, FC1Option]>,
-    HelpText<"Use the given vector functions library">,
+    HelpText<"Use the given vector functions library.\n"
+             "  Note: -fveclib=libmvec on AArch64 requires GLIBC 2.40 or newer.">,
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paulwalker-arm wrote:

The toolchain user will see a link time failure when trying to resolve a call to a vector math routine. Note: the exact requirement depends on the function in question, but version 2.40 is what was used to decide which math functions to add mappings for.

https://github.com/llvm/llvm-project/pull/146453