[clang] [CIR] Add is_implicit to ReturnOp (PR #174832)

[Hendrik Hübner via cfe-commits]

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@@ -714,10 +714,12 @@ def CIR_ReturnOp : CIR_Op<"return", [
 
   // The return operation takes an optional input operand to return. This
   // value must match the return type of the enclosing function.
-  let arguments = (ins Variadic<CIR_AnyType>:$input);
+  let arguments = (ins Variadic<CIR_AnyType>:$input, UnitProp:$is_implicit);
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HendrikHuebner wrote:

Could you update the description of `ReturnOp` with a short explanation of `is_implicit`?
This is only set for non-void functions missing return statements in C, right?

https://github.com/llvm/llvm-project/pull/174832