[flang-commits] [mlir] [flang] [MLIR][LLVM] Enable export of DISubprograms on function declarations (PR #78026)

[Christian Ulmann via flang-commits]

https://github.com/Dinistro created https://github.com/llvm/llvm-project/pull/78026

This commit changes the MLIR to LLVMIR export to also attach subprogram debug attachements to function declarations.
This commit additonally fixes the two passes that produce subprograms to not attach the "Definition" flag to function declarations. This otherwise results in invalid LLVM IR.

>From 9f9af8f96b9180214938b96969f91dbf8b27154b Mon Sep 17 00:00:00 2001
From: Christian Ulmann <christian.ulmann at nextsilicon.com>
Date: Sat, 13 Jan 2024 10:33:40 +0000
Subject: [PATCH] [MLIR][LLVM] Enable export of DISubprograms on function
 declarations

This commit changes the MLIR to LLVMIR export to also attach subprogram
debug attachements to function declarations.
This commit addiitonally fixes the two passes that produce subprograms
to not attach the "Definition" flag to function declarations. This
otherwise results in invalid LLVM IR.
---
 .../Optimizer/Transforms/AddDebugFoundation.cpp   |  8 +++++---
 .../LLVMIR/Transforms/DIScopeForLLVMFuncOp.cpp    | 15 ++++++++-------
 mlir/lib/Target/LLVMIR/ModuleTranslation.cpp      |  6 +++---
 mlir/test/Target/LLVMIR/llvmir-debug.mlir         | 14 ++++++++++++++
 4 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/flang/lib/Optimizer/Transforms/AddDebugFoundation.cpp b/flang/lib/Optimizer/Transforms/AddDebugFoundation.cpp
index 16b8db7ec8c640..7a6f58066722d5 100644
--- a/flang/lib/Optimizer/Transforms/AddDebugFoundation.cpp
+++ b/flang/lib/Optimizer/Transforms/AddDebugFoundation.cpp
@@ -97,16 +97,18 @@ void AddDebugFoundationPass::runOnOperation() {
     // Only definitions need a distinct identifier and a compilation unit.
     mlir::DistinctAttr id;
     mlir::LLVM::DICompileUnitAttr compilationUnit;
+    auto subprogramFlags = mlir::LLVM::DISubprogramFlags::Optimized;
     if (!funcOp.isExternal()) {
       id = mlir::DistinctAttr::create(mlir::UnitAttr::get(context));
       compilationUnit = cuAttr;
+      subprogramFlags =
+          subprogramFlags | mlir::LLVM::DISubprogramFlags::Definition;
     }
-    mlir::LLVM::DISubprogramAttr spAttr = mlir::LLVM::DISubprogramAttr::get(
+    auto spAttr = mlir::LLVM::DISubprogramAttr::get(
         context, id, compilationUnit, fileAttr, funcName, funcName,
         funcFileAttr,
         /*line=*/1,
-        /*scopeline=*/1, mlir::LLVM::DISubprogramFlags::Definition,
-        subTypeAttr);
+        /*scopeline=*/1, subprogramFlags, subTypeAttr);
     funcOp->setLoc(builder.getFusedLoc({funcOp->getLoc()}, spAttr));
   });
 }
diff --git a/mlir/lib/Dialect/LLVMIR/Transforms/DIScopeForLLVMFuncOp.cpp b/mlir/lib/Dialect/LLVMIR/Transforms/DIScopeForLLVMFuncOp.cpp
index de6fb1b16977a8..2960cc6220d9f5 100644
--- a/mlir/lib/Dialect/LLVMIR/Transforms/DIScopeForLLVMFuncOp.cpp
+++ b/mlir/lib/Dialect/LLVMIR/Transforms/DIScopeForLLVMFuncOp.cpp
@@ -67,18 +67,19 @@ static void addScopeToFunction(LLVM::LLVMFuncOp llvmFunc,
 
   StringAttr funcNameAttr = llvmFunc.getNameAttr();
   // Only definitions need a distinct identifier and a compilation unit.
-  mlir::DistinctAttr id;
-  if (!llvmFunc.isExternal())
+  DistinctAttr id;
+  auto subprogramFlags = LLVM::DISubprogramFlags::Optimized;
+  if (!llvmFunc.isExternal()) {
     id = mlir::DistinctAttr::create(mlir::UnitAttr::get(context));
-  else
+    subprogramFlags = subprogramFlags | LLVM::DISubprogramFlags::Definition;
+  } else {
     compileUnitAttr = {};
-  mlir::LLVM::DISubprogramAttr subprogramAttr = LLVM::DISubprogramAttr::get(
+  }
+  auto subprogramAttr = LLVM::DISubprogramAttr::get(
       context, id, compileUnitAttr, fileAttr, funcNameAttr, funcNameAttr,
       fileAttr,
       /*line=*/line,
-      /*scopeline=*/col,
-      LLVM::DISubprogramFlags::Definition | LLVM::DISubprogramFlags::Optimized,
-      subroutineTypeAttr);
+      /*scopeline=*/col, subprogramFlags, subroutineTypeAttr);
   llvmFunc->setLoc(FusedLoc::get(context, {loc}, subprogramAttr));
 }
 
diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
index ce46a194ea7d9f..7c23a7d3e9af4d 100644
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -1073,9 +1073,6 @@ LogicalResult ModuleTranslation::convertOneFunction(LLVMFuncOp func) {
   branchMapping.clear();
   llvm::Function *llvmFunc = lookupFunction(func.getName());
 
-  // Translate the debug information for this function.
-  debugTranslation->translate(func, *llvmFunc);
-
   // Add function arguments to the value remapping table.
   for (auto [mlirArg, llvmArg] :
        llvm::zip(func.getArguments(), llvmFunc->args()))
@@ -1256,6 +1253,9 @@ LogicalResult ModuleTranslation::convertFunctionSignatures() {
 
     if (auto alignment = function.getAlignment())
       llvmFunc->setAlignment(llvm::MaybeAlign(*alignment));
+
+    // Translate the debug information for this function.
+    debugTranslation->translate(function, *llvmFunc);
   }
 
   return success();
diff --git a/mlir/test/Target/LLVMIR/llvmir-debug.mlir b/mlir/test/Target/LLVMIR/llvmir-debug.mlir
index 476ed165887c08..f16c59f886500b 100644
--- a/mlir/test/Target/LLVMIR/llvmir-debug.mlir
+++ b/mlir/test/Target/LLVMIR/llvmir-debug.mlir
@@ -169,6 +169,20 @@ llvm.func @empty_types() {
 
 // -----
 
+#di_file = #llvm.di_file<"foo.mlir" in "/test/">
+#di_subprogram = #llvm.di_subprogram<
+  scope = #di_file, name = "func_decl_with_subprogram", file = #di_file, subprogramFlags = "Optimized"
+>
+
+// CHECK-LABEL: declare !dbg
+// CHECK-SAME: ![[SUBPROGRAM:.*]] i32 @func_decl_with_subprogram(
+llvm.func @func_decl_with_subprogram() -> (i32) loc(fused<#di_subprogram>["foo.mlir":2:1])
+
+// CHECK: ![[SUBPROGRAM]] = !DISubprogram(name: "func_decl_with_subprogram", scope: ![[FILE:.*]], file: ![[FILE]], spFlags: DISPFlagOptimized)
+// CHECK: ![[FILE:.*]] = !DIFile(filename: "foo.mlir", directory: "/test/")
+
+// -----
+
 #di_basic_type = #llvm.di_basic_type<tag = DW_TAG_base_type, name = "int", sizeInBits = 32, encoding = DW_ATE_signed>
 #di_file = #llvm.di_file<"foo.mlir" in "/test/">
 #di_compile_unit = #llvm.di_compile_unit<