commit 789e257ce0d84ef5ddbabfdf0c990b2878e67744
author Alexey Lapshin <a.v.lapshin@mail.ru> Sat Nov 30 23:48:32 2019 +0300
committer Alexey Lapshin <a.v.lapshin@mail.ru> Thu Dec 05 00:53:47 2019 +0300
tree ba5e426f2c4f121475cba871b3e386db6c72ab59
parent d6cbc9528d46d30416a6f9cd6c8570b704a0bd33

[DWARF5][Debuginfo] Compilation unit type (DW_UT_skeleton) and root DIE (DW_TAG_compile_unit) do not match.

That patch fixes incompatible compilation unit type (DW_UT_skeleton) and root DIE (DW_TAG_compile_unit) error.

cat split-dwarf.cpp
int main()
{
  int a = 1;
  return 0;
}

clang++ -O -g -gsplit-dwarf -gdwarf-5 split-dwarf.cpp; llvm-dwarfdump --verify ./a.out | grep skeleton
error: Compilation unit type (DW_UT_skeleton) and root DIE (DW_TAG_compile_unit) do not match.

The fix is to change DW_TAG_compile_unit into DW_TAG_skeleton_unit when skeleton file is generated.

Differential Revision: https://reviews.llvm.org/D70880

llvm/lib/CodeGen/AsmPrinter/DIE.cpp

diff --git a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
index c4d5b71..84b86a7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -319,8 +319,10 @@
 {
   Die.Owner = this;
   assert((UnitTag == dwarf::DW_TAG_compile_unit ||
+          UnitTag == dwarf::DW_TAG_skeleton_unit ||
           UnitTag == dwarf::DW_TAG_type_unit ||
-          UnitTag == dwarf::DW_TAG_partial_unit) && "expected a unit TAG");
+          UnitTag == dwarf::DW_TAG_partial_unit) &&
+         "expected a unit TAG");
 }
 
 void DIEValue::EmitValue(const AsmPrinter *AP) const {

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 9578e01..4e90c10 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -52,10 +52,23 @@
 
 using namespace llvm;
 
+static dwarf::Tag GetCompileUnitType(UnitKind Kind, DwarfDebug *DW) {
+
+  //  According to DWARF Debugging Information Format Version 5,
+  //  3.1.2 Skeleton Compilation Unit Entries:
+  //  "When generating a split DWARF object file (see Section 7.3.2
+  //  on page 187), the compilation unit in the .debug_info section
+  //  is a "skeleton" compilation unit with the tag DW_TAG_skeleton_unit"
+  if (DW->getDwarfVersion() >= 5 && Kind == UnitKind::Skeleton)
+    return dwarf::DW_TAG_skeleton_unit;
+
+  return dwarf::DW_TAG_compile_unit;
+}
+
 DwarfCompileUnit::DwarfCompileUnit(unsigned UID, const DICompileUnit *Node,
                                    AsmPrinter *A, DwarfDebug *DW,
-                                   DwarfFile *DWU)
-    : DwarfUnit(dwarf::DW_TAG_compile_unit, Node, A, DW, DWU), UniqueID(UID) {
+                                   DwarfFile *DWU, UnitKind Kind)
+    : DwarfUnit(GetCompileUnitType(Kind, DW), Node, A, DW, DWU), UniqueID(UID) {
   insertDIE(Node, &getUnitDie());
   MacroLabelBegin = Asm->createTempSymbol("cu_macro_begin");
 }

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 1b7ea26..8491d07 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -40,6 +40,8 @@
 class MCSymbol;
 class MDNode;
 
+enum class UnitKind { Skeleton, Full };
+
 class DwarfCompileUnit final : public DwarfUnit {
   /// A numeric ID unique among all CUs in the module
   unsigned UniqueID;
@@ -104,7 +106,8 @@
 
 public:
   DwarfCompileUnit(unsigned UID, const DICompileUnit *Node, AsmPrinter *A,
-                   DwarfDebug *DW, DwarfFile *DWU);
+                   DwarfDebug *DW, DwarfFile *DWU,
+                   UnitKind Kind = UnitKind::Full);
 
   bool hasRangeLists() const { return HasRangeLists; }
   unsigned getUniqueID() const { return UniqueID; }

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index a8fe696..bddb8bf 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2821,7 +2821,8 @@
 DwarfCompileUnit &DwarfDebug::constructSkeletonCU(const DwarfCompileUnit &CU) {
 
   auto OwnedUnit = std::make_unique<DwarfCompileUnit>(
-      CU.getUniqueID(), CU.getCUNode(), Asm, this, &SkeletonHolder);
+      CU.getUniqueID(), CU.getCUNode(), Asm, this, &SkeletonHolder,
+      UnitKind::Skeleton);
   DwarfCompileUnit &NewCU = *OwnedUnit;
   NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoSection());