[clang] [CIR] Upstream support for emitting constructors (PR #143639)

[Andy Kaylor via cfe-commits]

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@@ -21,6 +21,88 @@
 using namespace clang;
 using namespace clang::CIRGen;
 
+/// Checks whether the given constructor is a valid subject for the
+/// complete-to-base constructor delgation optimization, i.e. emitting the
+/// complete constructor as a simple call to the base constructor.
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andykaylor wrote:

Update: I was misunderstanding what `isDelegatingConstructor()` constructor meant. It's not the relevant case here. This function is only called for the C1 constructor (ctorType == Ctor_Complete) and it returns `true` for the initial test case here, causing us to emit the constructor as a call to the C2 constructor.

When I add a variadic constructor (which I will in my next update to this PR), this function returns `false` and we emit the C1 constructor (but not the C2 constructor).

https://github.com/llvm/llvm-project/pull/143639