[llvm] [LLVM][Support] add nonNull function helper (PR #188718)

[Nathan Gauër via llvm-commits]

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@@ -811,6 +811,19 @@ T cantFail(Expected<T> ValOrErr, const char *Msg = nullptr) {
   }
 }
 
+/// Calls llvm_unreachable if Pointer is null, otherwise returns the
+/// pointer as is.
+template <typename T>
+LLVM_ATTRIBUTE_RETURNS_NONNULL T *nonNull(T *Pointer,
+                                          const char *Msg = nullptr) {
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Keenuts wrote:

fair. Moved in the default value, just added an assert for Msg then.

https://github.com/llvm/llvm-project/pull/188718