[DWARFv5] Put the DWO ID in its place.

In DWARF v5, the DWO ID is in the (split/skeleton) CU header, not an
attribute on the CU DIE.

This changes the size of those headers, so use the parsed size whenever
we have one, for simplicitly.

Differential Revision: https://reviews.llvm.org/D47158

llvm-svn: 333004

3 files changed, 24 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index a4d699496b4..04c206ffea2 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -855,6 +855,8 @@ void DwarfCompileUnit::emitHeader(bool UseOffsets) {
                                 : DD->useSplitDwarf() ? dwarf::DW_UT_skeleton
                                                       : dwarf::DW_UT_compile;
   DwarfUnit::emitCommonHeader(UseOffsets, UT);
+  if (DD->getDwarfVersion() >= 5 && UT != dwarf::DW_UT_compile)
+    Asm->emitInt64(getDWOId());
 }
 
 bool DwarfCompileUnit::hasDwarfPubSections() const {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 60821c2cc99..5aea16acdc1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -83,6 +83,9 @@ class DwarfCompileUnit final : public DwarfUnit {
   DenseMap<const MDNode *, DIE *> AbstractSPDies;
   DenseMap<const MDNode *, std::unique_ptr<DbgVariable>> AbstractVariables;
 
+  /// DWO ID for correlating skeleton and split units.
+  uint64_t DWOId = 0;
+
   /// Construct a DIE for the given DbgVariable without initializing the
   /// DbgVariable's DIE reference.
   DIE *constructVariableDIEImpl(const DbgVariable &DV, bool Abstract);
@@ -219,6 +222,13 @@ public:
   /// Set the skeleton unit associated with this unit.
   void setSkeleton(DwarfCompileUnit &Skel) { Skeleton = &Skel; }
 
+  unsigned getHeaderSize() const override {
+    // DWARF v5 added the DWO ID to the header for split/skeleton units.
+    unsigned DWOIdSize =
+        DD->getDwarfVersion() >= 5 && DD->useSplitDwarf() ? sizeof(uint64_t)
+                                                          : 0;
+    return DwarfUnit::getHeaderSize() + DWOIdSize;
+  }
   unsigned getLength() {
     return sizeof(uint32_t) + // Length field
         getHeaderSize() + getUnitDie().getSize();
@@ -290,6 +300,9 @@ public:
   void setBaseAddress(const MCSymbol *Base) { BaseAddress = Base; }
   const MCSymbol *getBaseAddress() const { return BaseAddress; }
 
+  uint64_t getDWOId() const { return DWOId; }
+  void setDWOId(uint64_t DwoId) { DWOId = DwoId; }
+
   bool hasDwarfPubSections() const;
 };
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 4f61fca4343..258a6d36067 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -747,11 +747,15 @@ void DwarfDebug::finalizeModuleInfo() {
       // Emit a unique identifier for this CU.
       uint64_t ID =
           DIEHash(Asm).computeCUSignature(DWOName, TheCU.getUnitDie());
-      TheCU.addUInt(TheCU.getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
-                    dwarf::DW_FORM_data8, ID);
-      SkCU->addUInt(SkCU->getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
-                    dwarf::DW_FORM_data8, ID);
-
+      if (getDwarfVersion() >= 5) {
+        TheCU.setDWOId(ID);
+        SkCU->setDWOId(ID);
+      } else {
+        TheCU.addUInt(TheCU.getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
+                      dwarf::DW_FORM_data8, ID);
+        SkCU->addUInt(SkCU->getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
+                      dwarf::DW_FORM_data8, ID);
+      }
       // We don't keep track of which addresses are used in which CU so this
       // is a bit pessimistic under LTO.
       if (!AddrPool.isEmpty()) {