llvm · abidh · Sep 30, 2025 · Sep 29, 2025
diff --git a/flang/include/flang/Optimizer/Passes/Pipelines.h b/flang/include/flang/Optimizer/Passes/Pipelines.h
@@ -158,7 +158,8 @@ void createOpenMPFIRPassPipeline(mlir::PassManager &pm,
 void createDebugPasses(mlir::PassManager &pm,
                        llvm::codegenoptions::DebugInfoKind debugLevel,
                        llvm::OptimizationLevel OptLevel,
-                       llvm::StringRef inputFilename, int32_t dwarfVersion);
+                       llvm::StringRef inputFilename, int32_t dwarfVersion,
+                       llvm::StringRef splitDwarfFile);
 
 void createDefaultFIRCodeGenPassPipeline(mlir::PassManager &pm,
                                          MLIRToLLVMPassPipelineConfig config,

diff --git a/flang/include/flang/Optimizer/Transforms/Passes.td b/flang/include/flang/Optimizer/Transforms/Passes.td
@@ -246,6 +246,10 @@ def AddDebugInfo : Pass<"add-debug-info", "mlir::ModuleOp"> {
            "int32_t",
            /*default=*/"0",
            "dwarf version">,
+    Option<"splitDwarfFile", "split-dwarf-file",
+           "std::string", /*default=*/"std::string{}",
+           "Name of the split dwarf file">
+
   ];
 }
 

diff --git a/flang/include/flang/Tools/CrossToolHelpers.h b/flang/include/flang/Tools/CrossToolHelpers.h
@@ -109,6 +109,7 @@ struct MLIRToLLVMPassPipelineConfig : public FlangEPCallBacks {
       InstrumentFunctionExit = "__cyg_profile_func_exit";
     }
     DwarfVersion = opts.DwarfVersion;
+    SplitDwarfFile = opts.SplitDwarfFile;
   }
 
   llvm::OptimizationLevel OptLevel; ///< optimisation level
@@ -146,6 +147,7 @@ struct MLIRToLLVMPassPipelineConfig : public FlangEPCallBacks {
       Fortran::frontend::CodeGenOptions::ComplexRangeKind::
           CX_Full; ///< Method for calculating complex number division
   int32_t DwarfVersion = 0; ///< Version of DWARF debug info to generate
+  std::string SplitDwarfFile = ""; ///< File name for the split debug info
 };
 
 struct OffloadModuleOpts {

diff --git a/flang/lib/Optimizer/Passes/Pipelines.cpp b/flang/lib/Optimizer/Passes/Pipelines.cpp
@@ -95,12 +95,14 @@ getEmissionKind(llvm::codegenoptions::DebugInfoKind kind) {
 void addDebugInfoPass(mlir::PassManager &pm,
                       llvm::codegenoptions::DebugInfoKind debugLevel,
                       llvm::OptimizationLevel optLevel,
-                      llvm::StringRef inputFilename, int32_t dwarfVersion) {
+                      llvm::StringRef inputFilename, int32_t dwarfVersion,
+                      llvm::StringRef splitDwarfFile) {
   fir::AddDebugInfoOptions options;
   options.debugLevel = getEmissionKind(debugLevel);
   options.isOptimized = optLevel != llvm::OptimizationLevel::O0;
   options.inputFilename = inputFilename;
   options.dwarfVersion = dwarfVersion;
+  options.splitDwarfFile = splitDwarfFile;
   addPassConditionally(pm, disableDebugInfo,
                        [&]() { return fir::createAddDebugInfoPass(options); });
 }
@@ -340,9 +342,11 @@ void createOpenMPFIRPassPipeline(mlir::PassManager &pm,
 void createDebugPasses(mlir::PassManager &pm,
                        llvm::codegenoptions::DebugInfoKind debugLevel,
                        llvm::OptimizationLevel OptLevel,
-                       llvm::StringRef inputFilename, int32_t dwarfVersion) {
+                       llvm::StringRef inputFilename, int32_t dwarfVersion,
+                       llvm::StringRef splitDwarfFile) {
   if (debugLevel != llvm::codegenoptions::NoDebugInfo)
-    addDebugInfoPass(pm, debugLevel, OptLevel, inputFilename, dwarfVersion);
+    addDebugInfoPass(pm, debugLevel, OptLevel, inputFilename, dwarfVersion,
+                     splitDwarfFile);
 }
 
 void createDefaultFIRCodeGenPassPipeline(mlir::PassManager &pm,
@@ -360,7 +364,7 @@ void createDefaultFIRCodeGenPassPipeline(mlir::PassManager &pm,
       pm, (config.DebugInfo != llvm::codegenoptions::NoDebugInfo));
   fir::addExternalNameConversionPass(pm, config.Underscoring);
   fir::createDebugPasses(pm, config.DebugInfo, config.OptLevel, inputFilename,
-                         config.DwarfVersion);
+                         config.DwarfVersion, config.SplitDwarfFile);
   fir::addTargetRewritePass(pm);
   fir::addCompilerGeneratedNamesConversionPass(pm);
 

diff --git a/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp b/flang/lib/Optimizer/Transforms/AddDebugInfo.cpp
@@ -696,7 +696,8 @@ void AddDebugInfoPass::runOnOperation() {
       llvm::dwarf::getLanguage("DW_LANG_Fortran95"), fileAttr, producer,
       isOptimized, debugLevel,
       /*nameTableKind=*/mlir::LLVM::DINameTableKind::Default,
-      /*splitDebugFilename=*/mlir::StringAttr());
+      splitDwarfFile.empty() ? mlir::StringAttr()
+                             : mlir::StringAttr::get(context, splitDwarfFile));
 
   module.walk([&](mlir::func::FuncOp funcOp) {
     handleFuncOp(funcOp, fileAttr, cuAttr, typeGen, &symbolTable);

diff --git a/flang/test/Integration/debug-split-dwarf.f90 b/flang/test/Integration/debug-split-dwarf.f90
@@ -2,20 +2,28 @@
 
 ! Testing to ensure that setting only -split-dwarf-file allows to place
 ! .dwo sections into regular output object.
-!  RUN: %flang_fc1 -debug-info-kind=standalone -triple x86_64-unknown-linux \
-!  RUN:   -split-dwarf-file %t.o -emit-obj -o %t.o %s
-!  RUN: llvm-readobj -S %t.o | FileCheck --check-prefix=DWO %s
+! RUN: %flang_fc1 -debug-info-kind=standalone -triple x86_64-unknown-linux \
+! RUN:   -split-dwarf-file %t.o -emit-obj -o %t.o %s
+! RUN: llvm-readobj -S %t.o | FileCheck --check-prefix=DWO %s
 
 ! Testing to ensure that setting both -split-dwarf-file and -split-dwarf-output
 ! does not place .dwo sections into regular output object but in a separate
 ! file.
-!  RUN: %flang_fc1 -debug-info-kind=standalone -triple x86_64-unknown-linux \
-!  RUN:   -split-dwarf-file %t.dwo -split-dwarf-output %t.dwo -emit-obj -o %t.o %s
-!  RUN: llvm-readobj -S %t.dwo | FileCheck --check-prefix=DWO %s
-!  RUN: llvm-readobj -S %t.o | FileCheck --check-prefix=SPLIT %s
+! RUN: %flang_fc1 -debug-info-kind=standalone -triple x86_64-unknown-linux \
+! RUN:   -split-dwarf-file %t.dwo -split-dwarf-output %t.dwo -emit-obj -o %t.o %s
+! RUN: llvm-readobj -S %t.dwo | FileCheck --check-prefix=DWO %s
+! RUN: llvm-readobj -S %t.o | FileCheck --check-prefix=SPLIT %s
 
-!  DWO: .dwo
-!  SPLIT-NOT: .dwo
+! Test that splitDebugFilename field of the DICompileUnit get correctly
+! generated.
+! RUN: %flang_fc1 -debug-info-kind=standalone -triple x86_64-unknown-linux \
+! RUN:   -split-dwarf-file %t.test_dwo -split-dwarf-output %t.test_dwo \
+! RUN:   -emit-llvm %s -o - | FileCheck --check-prefix=CU %s
+
+! DWO: .dwo
+! SPLIT-NOT: .dwo
+! CU: !DICompileUnit
+! CU-SAME: splitDebugFilename: "{{.*}}test_dwo"
 
 program test
 end program test
diff --git a/flang/test/Transforms/debug-split-dwarf.fir b/flang/test/Transforms/debug-split-dwarf.fir
@@ -0,0 +1,12 @@
+// RUN: fir-opt --add-debug-info="split-dwarf-file=test.dwo"  \
+// RUN:         --mlir-print-debuginfo %s -o - | FileCheck %s
+
+module {
+  func.func @test() {
+    return
+  } loc(#loc1)
+}
+#loc1 = loc("test.f90":15:1)
+
+// CHECK: llvm.di_compile_unit
+// CHECK-SAME: splitDebugFilename = "test.dwo"