[clang] [DebugInfo] Ignore delegating constructors in constructor homing. (PR #218807)

[Clayton Knittel via cfe-commits]

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@@ -27,6 +27,39 @@ struct E {
   constexpr E(){};
 } TestE;
 
+// Defined delegating constructor where delegated constructor is not defined
+// should not emit full debug info.
+// CHECK-DAG: !DICompositeType(tag: DW_TAG_structure_type, name: "Delegating"{{.*}}flags: DIFlagFwdDecl
+struct Delegating {
+  Delegating() : Delegating(42) {}
+  Delegating(int);
+} TestDelegating;
+
+// Defined delegating constructor where delegated constructor is defined should
+// emit full debug info.
+// CHECK-DAG: !DICompositeType(tag: DW_TAG_structure_type, name: "DelegatingToDefined"{{.*}}DIFlagTypePassByValue
+struct DelegatingToDefined {
+  DelegatingToDefined() : DelegatingToDefined(42) {}
+  DelegatingToDefined(int) {}
+} TestDelegatingToDefined;
+
+// Defined out-of-line delegating constructor where delegated constructor is
+// defined should emit full debug info.
+// CHECK-DAG: !DICompositeType(tag: DW_TAG_structure_type, name: "DelegatingOutOfLine"{{.*}}DIFlagTypePassByValue
+struct DelegatingOutOfLine {
+  DelegatingOutOfLine();
+  DelegatingOutOfLine(int) {}
+};
+DelegatingOutOfLine d;
+DelegatingOutOfLine::DelegatingOutOfLine() : DelegatingOutOfLine(42) {}
----------------
ClaytonKnittel wrote:

Yep, the tests should already cover these cases I believe.

It essentially boils down to this - all delegating constructors are ignored. Otherwise, the normal rules apply for constructor homing.

`DelegatingToOutOfLine` has a delegating ctor that calls another ctor which is defined out-of-line. Full debug info is emitted because, ignoring the delegating ctor, we can see the definition of a ctor.

And `DelegatingOutOfLine` has a defined out-of-line delegating ctor that calls an inline-defined ctor. Also emit full debug info. This is the same as the previous test, we just switched which ctors were defined inline vs. out-of-line.

`Delegating` is the only test case that doesn't emit full debug info. It has a delegating ctor that calls a ctor which is not defined. It does not emit full debug info, which is what we expected.

Let me know if there are any more cases you'd like to test. We have coverage of delegating-to-declared (`Delegating`) and delegating-to-defined (all other cases), with some combinations of defining ctors inline vs out-of-line (which shouldn't make a difference on whether full debug info is emitted).

https://github.com/llvm/llvm-project/pull/218807