[PATCH] D63361: Pretend NRVO variables are references so they can be found by debug info

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

This needs two unit tests:

- A clang test at `clang/test/CodeGenCXX/debug-info-nrvo.cpp` similar to other debug-info-* tests there. This test should have a second RUN line and extra checks for -fno-elide-constructors.
- An LLVM test at `llvm/test/DebugInfo/COFF/nrvo.ll` to show that we handle dbg.declare + deref

Truly, we should also test the inalloca case.



================
Comment at: clang/lib/CodeGen/CGDebugInfo.cpp:3946
+  // the address of the variable.
+  if (VD->isNRVOVariable())
+    Expr.push_back(llvm::dwarf::DW_OP_deref);
----------------
I think we should check for `getLangOpts().ElideConstructors` here, and check that the debug info is correct (no deref) in that mode.


================
Comment at: clang/lib/CodeGen/CodeGenFunction.cpp:908
     --EI;
     llvm::Value *Addr = Builder.CreateStructGEP(nullptr, &*EI, Idx);
     Addr = Builder.CreateAlignedLoad(Addr, getPointerAlign(), "agg.result");
----------------
What I had in mind was to use this GEP as the ReturnValuePointer here. The inalloca parameter is also a pointer to stack memory, and a GEP is an offset, so it should end up being handled like a static alloca.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D63361/new/

https://reviews.llvm.org/D63361