[clang] [CIR] Implement ctor-try-body rethrow (PR #229436)

[Erich Keane via cfe-commits]

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@@ -736,8 +741,13 @@ CIRGenFunction::emitCXXTryStmt(const CXXTryStmt &s,
     //   The currently handled exception is rethrown if control
     //   reaches the end of a handler of the function-try-block of a
     //   constructor or destructor.
-
-    // TODO(cir): Handle implicit rethrow?
+    //
+    // It is important that we only do this on fallthrough and not on
+    // return.  Note that it's illegal to put a return in a
+    // constructor function-try-block's catch handler (p14), so this
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erichkeane wrote:

This comment is copy/pasted from classic codegen :)  See CGException.cpp:1301.

https://github.com/llvm/llvm-project/pull/229436