[flang-commits] [flang] [flang][debug] Handle 'used' module. (PR #107626)

[via flang-commits]

================
@@ -152,6 +156,44 @@ mlir::LLVM::DIModuleAttr AddDebugInfoPass::getOrCreateModuleAttr(
   return modAttr;
 }
 
+/// If globalOp represents a module variable, return a ModuleAttr that
+/// represents that module.
+std::optional<mlir::LLVM::DIModuleAttr>
+AddDebugInfoPass::getModuleAttrFromGlobalOp(fir::GlobalOp globalOp,
+                                            mlir::LLVM::DIFileAttr fileAttr,
+                                            mlir::LLVM::DIScopeAttr scope) {
+  mlir::MLIRContext *context = &getContext();
+  mlir::OpBuilder builder(context);
+
+  std::pair result = fir::NameUniquer::deconstruct(globalOp.getSymName());
+  // Only look for module if this variable is not part of a function.
+  if (!result.second.procs.empty() || result.second.modules.empty())
+    return std::nullopt;
+
+  // DWARF5 says following about the fortran modules:
+  // A Fortran 90 module may also be represented by a module entry
+  // (but no declaration attribute is warranted because Fortran has no concept
+  // of a corresponding module body).
+  // But in practice, compilers use declaration attribute with a module in cases
+  // where module was defined in another source file (only being used in this
+  // one). The isInitialized() seems to provide the right information
+  // but inverted. It is true where module is actually defined but false where
+  // it is used.
+  // FIXME: Currently we don't have the line number on which a module was
+  // declared. We are using a best guess of line - 1 where line is the source
+  // line of the first member of the module that we encounter.
+  unsigned line = getLineFromLoc(globalOp.getLoc());
+
+  mlir::LLVM::DISubprogramAttr sp =
+      mlir::dyn_cast_if_present<mlir::LLVM::DISubprogramAttr>(scope);
+  // Modules are generated at compile unit scope
+  if (sp)
+    scope = sp.getCompileUnit();
+
+  return getOrCreateModuleAttr(result.second.modules[0], fileAttr, scope,
+                               line - 1, !globalOp.isInitialized());
----------------
jeanPerier wrote:

`line-1` could be 0 if the variable name appeared on the first line of the file as below. It may be best to use `std::max(line - 1, 1)` to avoid troubles.

```
  use m, only : x
  call bar(x)
end
```

https://github.com/llvm/llvm-project/pull/107626