[compiler-rt] [Clang] Add __builtin_vectorelements to get number of elements in vector (PR #69010)

[Lawrence Benson via llvm-commits]

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@@ -10136,6 +10136,9 @@ def err_vec_builtin_incompatible_vector : Error<
 def err_vsx_builtin_nonconstant_argument : Error<
   "argument %0 to %1 must be a 2-bit unsigned literal (i.e. 0, 1, 2 or 3)">;
 
+def err_vectorelements_non_vector : Error<
+ "'__builtin_vectorelements' argument must be a vector">;
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lawben wrote:

this was inspired by "`first argument to __builtin_convertvector must be a vector`". but if you have a suggestion, i'm happy to change this. 

https://github.com/llvm/llvm-project/pull/69010