[clang] [Wasm][Clang] Add __builtin_wasm_ref_is_null_extern (PR #139580)

[Hood Chatham via cfe-commits]

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@@ -741,6 +741,12 @@ __externref_t externref_null() {
   // WEBASSEMBLY-NEXT: ret
 }
 
+int externref_is_null(__externref_t arg) {
+  return __builtin_wasm_ref_is_null_extern(arg);
+  // WEBASSEMBLY: tail call i32 @llvm.wasm.ref.is_null.extern(ptr addrspace(10) %arg)
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hoodmane wrote:

Yeah @pmatos implemented it four years ago:
https://reviews.llvm.org/D114979

https://github.com/llvm/llvm-project/pull/139580