[Cloning] Clone every Function's Debug Info

Summary:
Export the CloneDebugInfoMetadata utility, which clones all debug info
associated with a function into the first module. Also use this function
in CloneModule on each function we clone (the CloneFunction entrypoint
already does this).

Without this, cloning a module will lead to DI quality regressions,
especially since r252219 reversed the Function <-> DISubprogram edge
(before we could get lucky and have this edge preserved if the
DISubprogram itself was, e.g. due to location metadata).

This was verified to fix missing debug information in julia and
a unittest to verify the new behavior is included.

Patch by Yichao Yu! Thanks!

Reviewers: loladiro, pcc
Differential Revision: http://reviews.llvm.org/D17165

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260791 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Utils/Cloning.h

@@ -130,6 +130,11 @@ Function *CloneFunction(const Function *F, ValueToValueMapTy &VMap,
                         bool ModuleLevelChanges,
                         ClonedCodeInfo *CodeInfo = nullptr);
 
+/// Clone the module-level debug info associated with OldFunc. The cloned data
+/// will point to NewFunc instead.
+void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
+                            ValueToValueMapTy &VMap);
+
 /// Clone OldFunc into NewFunc, transforming the old arguments into references
 /// to VMap values.  Note that if NewFunc already has basic blocks, the ones
 /// cloned into it will be added to the end of the function.  This function

lib/Transforms/Utils/CloneFunction.cpp

@@ -187,8 +187,8 @@ static void AddOperand(DICompileUnit *CU, DISubprogramArray SPs,
 
 // Clone the module-level debug info associated with OldFunc. The cloned data
 // will point to NewFunc instead.
-static void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
-                            ValueToValueMapTy &VMap) {
+void llvm::CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
+                                  ValueToValueMapTy &VMap) {
   DebugInfoFinder Finder;
   Finder.processModule(*OldFunc->getParent());
 

lib/Transforms/Utils/CloneModule.cpp

@@ -136,6 +136,7 @@ std::unique_ptr<Module> llvm::CloneModule(
         VMap[&*J] = &*DestI++;
       }
 
+      CloneDebugInfoMetadata(F, &*I, VMap);
       SmallVector<ReturnInst*, 8> Returns;  // Ignore returns cloned.
       CloneFunctionInto(F, &*I, VMap, /*ModuleLevelChanges=*/true, Returns);
     }

unittests/Transforms/Utils/Cloning.cpp

@@ -423,6 +423,7 @@ protected:
   void SetupModule() { OldM = new Module("", C); }
 
   void CreateOldModule() {
+    DIBuilder DBuilder(*OldM);
     IRBuilder<> IBuilder(C);
 
     auto *FuncType = FunctionType::get(Type::getVoidTy(C), false);
@@ -431,9 +432,25 @@ protected:
     auto *F =
         Function::Create(FuncType, GlobalValue::PrivateLinkage, "f", OldM);
     F->setPersonalityFn(PersFn);
+
+    // Create debug info
+    auto *File = DBuilder.createFile("filename.c", "/file/dir/");
+    DITypeRefArray ParamTypes = DBuilder.getOrCreateTypeArray(None);
+    DISubroutineType *DFuncType = DBuilder.createSubroutineType(ParamTypes);
+    auto *CU =
+        DBuilder.createCompileUnit(dwarf::DW_LANG_C99, "filename.c",
+                                   "/file/dir", "CloneModule", false, "", 0);
+    // Function DI
+    auto *Subprogram = DBuilder.createFunction(CU, "f", "f", File, 4, DFuncType,
+                                               true, true, 3, 0, false);
+    F->setSubprogram(Subprogram);
+
     auto *Entry = BasicBlock::Create(C, "", F);
     IBuilder.SetInsertPoint(Entry);
     IBuilder.CreateRetVoid();
+
+    // Finalize the debug info
+    DBuilder.finalize();
   }
 
   void CreateNewModule() { NewM = llvm::CloneModule(OldM).release(); }
@@ -447,4 +464,12 @@ TEST_F(CloneModule, Verify) {
   EXPECT_FALSE(verifyModule(*NewM));
 }
 
+TEST_F(CloneModule, Subprogram) {
+  Function *NewF = NewM->getFunction("f");
+  DISubprogram *SP = NewF->getSubprogram();
+  EXPECT_TRUE(SP != nullptr);
+  EXPECT_EQ(SP->getName(), "f");
+  EXPECT_EQ(SP->getFile()->getFilename(), "filename.c");
+  EXPECT_EQ(SP->getLine(), (unsigned)4);
+}
 }