[clang] [CIR] Add token.none and fix coro.end signature (PR #214125)

[Erich Keane via cfe-commits]

================
@@ -8734,6 +8734,24 @@ def CIR_ConstructCatchParamOp : CIR_Op<"construct_catch_param", [
   let hasLLVMLowering = false;
 }
 
+//===----------------------------------------------------------------------===//
+// TokenNoneOp
+//===----------------------------------------------------------------------===//
+
+def CIR_TokenNoneOp : CIR_Op<"token.none", [
+  Pure, TokenProducerTrait
+]> {
+  let summary = "Produces an empty token value.";
+  let description = [{
+    MLIR does not have a way to represent the LLVM IR `none` token literal.
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erichkeane wrote:

This whole description isn't in the right 'voice'?  Can we just explain what it means/does rather than be concerned about MLIR?

https://github.com/llvm/llvm-project/pull/214125