[clang] [clang][DebugInfo] Add inlined subprogram metadata for compiler built-ins (PR #189969)

[J. Ryan Stinnett via cfe-commits]

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@@ -2648,6 +2648,11 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
   assert(!getContext().BuiltinInfo.isImmediate(BuiltinID) &&
          "Should not codegen for consteval builtins");
 
+  // Treat built-in as call to artificial inlined function in debug info.
+  // This enables e.g. profiling tools to annotate time spent in user-called
+  // built-ins with the built-in function name.
+  ApplyBuiltinDebugLocation DebugScope(*this, GD);
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jryans wrote:

Hmm, do you have a particular example in mind? Even single intrinsics can lead to a wide variety of behaviours further down the pipeline, depending on their purpose.

I believe it will be hard to "automatically" scope this to only certain built-ins based on their ultimate behaviour at this front-end emission stage because those behaviours are determined by other passes further down the pipeline and this Clang code gen stage is unaware of them. 

If we do decide to apply this to only some built-ins, perhaps the simplest way to do so at this point in the pipeline would be via an explicit list of built-ins that we do not want to apply this to (based on what we assume about how they behave).

Anyway, it may help to talk through one or more examples, so I am curious which you have in mind.

https://github.com/llvm/llvm-project/pull/189969