[flang-commits] [flang] [flang][debug] Only import debug info for specified renamed variables (PR #194926)

[via flang-commits]

https://github.com/timsmith78 updated https://github.com/llvm/llvm-project/pull/194926

>From 07623b498311cac4fc062c0a0da5f190bec26eb1 Mon Sep 17 00:00:00 2001
From: Timothy Smith <timothy.smith at hpe.com>
Date: Thu, 23 Apr 2026 11:58:41 -0500
Subject: [PATCH 1/2] Only import debug info for specified renamed variables

Given the following:

USE mod, ONLY : alias => var

Currently, flang will create a DW_TAG_imported_module tag for mod when
it should only be creating a list of DW_TAG_imported_declaration tags
for each imported variable.  This causes erroneous variables from mod to be
visible in the debugger with undefined information.

Fixes #180836
---
 flang/lib/Lower/PFTBuilder.cpp                  | 1 +
 flang/lib/Optimizer/Transforms/AddDebugInfo.cpp | 8 ++++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/flang/lib/Lower/PFTBuilder.cpp b/flang/lib/Lower/PFTBuilder.cpp
index afabb6b29f4f1..367b516bdcdac 100644
--- a/flang/lib/Lower/PFTBuilder.cpp
+++ b/flang/lib/Lower/PFTBuilder.cpp
@@ -253,6 +253,7 @@ class PFTBuilder {
                             std::string localName{
                                 std::get<0>(names.t).source.ToString()};
                             stmt.renames.push_back(localName);
+                            stmt.onlyNames.push_back(localName);
                           },
                           [&](const parser::Rename::Operators &) {
                             // Operator renames - not commonly needed for debug
diff --git a/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp b/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
index 65c8508de9c9f..167ce0c5f0acd 100644
--- a/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
+++ b/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
@@ -823,8 +823,12 @@ void AddDebugInfoPass::handleOnlyClause(
     fir::UseStmtOp useOp, mlir::LLVM::DISubprogramAttr spAttr,
     mlir::LLVM::DIFileAttr fileAttr, mlir::SymbolTable *symbolTable,
     llvm::DenseSet<mlir::LLVM::DIImportedEntityAttr> &importedModules) {
+
+  auto onlySymbols = useOp.getOnlySymbols();
+  auto renames = useOp.getRenames();
+
   // Process ONLY symbols (without renames)
-  if (auto onlySymbols = useOp.getOnlySymbols()) {
+  if (onlySymbols && !renames) {
     for (mlir::Attribute attr : *onlySymbols) {
       auto symbolRef = mlir::cast<mlir::FlatSymbolRefAttr>(attr);
       if (auto importedDecl = createImportedDeclForGlobal(
@@ -835,7 +839,7 @@ void AddDebugInfoPass::handleOnlyClause(
   }
 
   // Process renames within ONLY clause
-  if (auto renames = useOp.getRenames()) {
+  if (renames) {
     for (auto attr : *renames) {
       auto renameAttr = mlir::cast<fir::UseRenameAttr>(attr);
       if (auto importedDecl = createImportedDeclForGlobal(

>From 6943088b3f8b7a4fa1caaa2dc3953216f0786bc7 Mon Sep 17 00:00:00 2001
From: Timothy Smith <timothy.smith at hpe.com>
Date: Fri, 1 May 2026 15:01:26 -0500
Subject: [PATCH 2/2] Fix cases where USE, ONLY clause contains mix of renames
 and non-renames

---
 .../lib/Optimizer/Transforms/AddDebugInfo.cpp | 20 +++++++++++++++++--
 flang/test/Integration/debug-use-stmt.f90     |  2 ++
 flang/test/Lower/debug-use-stmt.f90           |  4 ++--
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp b/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
index 167ce0c5f0acd..09efc27f93368 100644
--- a/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
+++ b/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
@@ -828,10 +828,26 @@ void AddDebugInfoPass::handleOnlyClause(
   auto renames = useOp.getRenames();
 
   // Process ONLY symbols (without renames)
-  if (onlySymbols && !renames) {
+  if (onlySymbols) {
     for (mlir::Attribute attr : *onlySymbols) {
       auto symbolRef = mlir::cast<mlir::FlatSymbolRefAttr>(attr);
-      if (auto importedDecl = createImportedDeclForGlobal(
+
+      // Check if this symbol is also in renames, if so skip it
+      bool isInRenames = false;
+      if (renames) {
+        for (auto renameAttr : *renames) {
+          auto rename = mlir::cast<fir::UseRenameAttr>(renameAttr);
+          if (rename.getSymbol().getValue() == symbolRef.getValue()) {
+            isInRenames = true;
+            break;
+          }
+        }
+      }
+
+    if (isInRenames)
+      continue;
+
+    if (auto importedDecl = createImportedDeclForGlobal(
               symbolRef.getValue(), spAttr, fileAttr, mlir::StringAttr(),
               symbolTable))
         importedModules.insert(*importedDecl);
diff --git a/flang/test/Integration/debug-use-stmt.f90 b/flang/test/Integration/debug-use-stmt.f90
index db20dd94e85d1..50a70da3941f8 100644
--- a/flang/test/Integration/debug-use-stmt.f90
+++ b/flang/test/Integration/debug-use-stmt.f90
@@ -26,6 +26,8 @@ program test_use
 
 ! CHECK-DAG: [[SP:![0-9]+]] = distinct !DISubprogram(name: "TEST_USE", linkageName: "_QQmain"{{.*}}retainedNodes:
 
+! Check that the full testmod module is not imported
+! CHECK-NOT: !DIImportedEntity(tag: DW_TAG_imported_module, scope: [[SP]], entity: [[TESTMOD]]
 ! Check testmod imports: var_b directly (no rename), var_d as rename of var_c
 ! CHECK-DAG: !DIImportedEntity(tag: DW_TAG_imported_declaration, scope: [[SP]], entity: [[VAR_B]],{{.*}}file:{{.*}}line:
 ! CHECK-DAG: !DIImportedEntity(tag: DW_TAG_imported_declaration, name: "var_d", scope: [[SP]], entity: [[VAR_C]],{{.*}}file:{{.*}}line:
diff --git a/flang/test/Lower/debug-use-stmt.f90 b/flang/test/Lower/debug-use-stmt.f90
index 293b38c78e17a..7404f7da932ea 100644
--- a/flang/test/Lower/debug-use-stmt.f90
+++ b/flang/test/Lower/debug-use-stmt.f90
@@ -73,8 +73,8 @@ subroutine test_only_rename()
 ! NO_DEBUG-NOT: fir.use_stmt
 
 ! WITH_DEBUG-LABEL: func.func @_QPtest_only_rename()
-! WITH_DEBUG-DAG: fir.use_stmt "mod1" only_symbols{{\[}}[@_QMmod1Ec]] renames{{\[}}[#fir.use_rename<"local_b", @_QMmod1Eb>, #fir.use_rename<"local_a", @_QMmod1Ea>]]
-! WITH_DEBUG-DAG: fir.use_stmt "mod2" renames{{\[}}[#fir.use_rename<"local_x", @_QMmod2Ex>, #fir.use_rename<"local_y", @_QMmod2Ey>]]
+! WITH_DEBUG-DAG: fir.use_stmt "mod1" only_symbols{{\[}}[@_QMmod1Eb, @_QMmod1Ec, @_QMmod1Ea]] renames{{\[}}[#fir.use_rename<"local_b", @_QMmod1Eb>, #fir.use_rename<"local_a", @_QMmod1Ea>]]
+! WITH_DEBUG-DAG: fir.use_stmt "mod2" only_symbols{{\[}}[@_QMmod2Ex, @_QMmod2Ey]] renames{{\[}}[#fir.use_rename<"local_x", @_QMmod2Ex>, #fir.use_rename<"local_y", @_QMmod2Ey>]]
 
 ! NO_DEBUG-LABEL: func.func @_QPtest_only_rename()
 ! NO_DEBUG-NOT: fir.use_stmt