[flang-commits] [flang] Reland [flang][debug] Emit debug info for named constants- #213974 (PR #215369)

[Eugene Epshteyn via flang-commits]

================
@@ -510,8 +521,27 @@ void AddDebugInfoPass::handleGlobalOp(fir::GlobalOp globalOp,
   mlir::OpBuilder builder(context);
 
   std::pair result = fir::NameUniquer::deconstruct(globalOp.getSymName());
-  if (result.first != fir::NameUniquer::NameKind::VARIABLE)
+  switch (result.first) {
+  case fir::NameUniquer::NameKind::VARIABLE:
+    break;
+  case fir::NameUniquer::NameKind::CONSTANT:
+    // A constant local to a procedure is described while walking that
+    // procedure, where `scope` is its DISubprogramAttr. Reaching here with any
+    // other scope means the procedure is not in the IR, typically because it
+    // was never called and got removed while its constant survived. There is
+    // no procedure to attach the constant to, and describing it at compile
+    // unit scope would wrongly make it visible everywhere.
+    if (!isModuleLevelName(result.second) &&
+        !mlir::isa<mlir::LLVM::DISubprogramAttr>(scope))
+      return;
+    // Don't describe a constant for which we only have a declaration. It could
----------------
eugeneepshteyn wrote:

Please check the following case:

Module:
```
module mdef
  implicit none
  integer, parameter :: kk = 11
  integer, parameter :: tbl(4) = [1,2,3,4]
  integer :: mvar = 7
end module mdef
```
This is the regular use of the module, should work fine with the current change:
```
program uall
  use mdef
  implicit none
  print *, kk, tbl(2), mvar
end program uall
```
This is USE/ONLY case. Does it still work?
```
program uonly
  use mdef, only: kk, tbl, mvar
  ! Try variations: use all module declarations with ONLY, then use various subsets.
  implicit none
  ! Only print things that appear in ONLY:
  print *, kk, tbl(2), mvar
end program uonly
```


https://github.com/llvm/llvm-project/pull/215369