In Dwarf 3 (and Dwarf 2) attributes whose value are offsets into a

section use the form DW_FORM_data4 whilst in Dwarf 4 and later they
use the form DW_FORM_sec_offset.

This patch updates the places where such attributes are generated to
use the appropriate form depending on the Dwarf version. The DIE entries
affected have the following tags:
DW_AT_stmt_list, DW_AT_ranges, DW_AT_location, DW_AT_GNU_pubnames,
DW_AT_GNU_pubtypes, DW_AT_GNU_addr_base, DW_AT_GNU_ranges_base

It also adds a hidden command line option "--dwarf-version=<uint>"
to llc which allows the version of Dwarf to be generated to override
what is specified in the metadata; this makes it possible to update
existing tests to check the debugging information generated for both
Dwarf 4 (the default) and Dwarf 3 using the same metadata.

Patch (slightly modified) by Keith Walker!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195391 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 92 insertions, 52 deletions

diff --git a/lib/CodeGen/AsmPrinter/DIE.cpp b/lib/CodeGen/AsmPrinter/DIE.cpp
index b1bcf7c63f..8a7b8608b7 100644
--- a/lib/CodeGen/AsmPrinter/DIE.cpp
+++ b/lib/CodeGen/AsmPrinter/DIE.cpp
@@ -341,6 +341,7 @@ void DIEDelta::EmitValue(AsmPrinter *AP, dwarf::Form Form) const {
 ///
 unsigned DIEDelta::SizeOf(AsmPrinter *AP, dwarf::Form Form) const {
   if (Form == dwarf::DW_FORM_data4) return 4;
+  if (Form == dwarf::DW_FORM_sec_offset) return 4;
   if (Form == dwarf::DW_FORM_strp) return 4;
   return AP->getDataLayout().getPointerSize();
 }
diff --git a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index a63968c441..73d0a839a7 100644
--- a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -245,6 +245,26 @@ void CompileUnit::addLabel(DIEBlock *Die, dwarf::Form Form,
   addLabel(Die, (dwarf::Attribute)0, Form, Label);
 }
 
+/// addSectionLabel - Add a Dwarf section label attribute data and value.
+///
+void CompileUnit::addSectionLabel(DIE *Die, dwarf::Attribute Attribute,
+                                  const MCSymbol *Label) {
+  if (DD->getDwarfVersion() >= 4)
+    addLabel(Die, Attribute, dwarf::DW_FORM_sec_offset, Label);
+  else
+    addLabel(Die, Attribute, dwarf::DW_FORM_data4, Label);
+}
+
+/// addSectionOffset - Add an offset into a section attribute data and value.
+///
+void CompileUnit::addSectionOffset(DIE *Die, dwarf::Attribute Attribute,
+                                   uint64_t Integer) {
+  if (DD->getDwarfVersion() >= 4)
+    addUInt(Die, Attribute, dwarf::DW_FORM_sec_offset, Integer);
+  else
+    addUInt(Die, Attribute, dwarf::DW_FORM_data4, Integer);
+}
+
 /// addLabelAddress - Add a dwarf label attribute data and value using
 /// DW_FORM_addr or DW_FORM_GNU_addr_index.
 ///
@@ -282,13 +302,15 @@ void CompileUnit::addOpAddress(DIEBlock *Die, const MCSymbol *Sym) {
   }
 }
 
-/// addDelta - Add a label delta attribute data and value.
+/// addSectionDelta - Add a section label delta attribute data and value.
 ///
-void CompileUnit::addDelta(DIE *Die, dwarf::Attribute Attribute,
-                           dwarf::Form Form, const MCSymbol *Hi,
-                           const MCSymbol *Lo) {
+void CompileUnit::addSectionDelta(DIE *Die, dwarf::Attribute Attribute,
+                                  const MCSymbol *Hi, const MCSymbol *Lo) {
   DIEValue *Value = new (DIEValueAllocator) DIEDelta(Hi, Lo);
-  Die->addValue(Attribute, Form, Value);
+  if (DD->getDwarfVersion() >= 4)
+    Die->addValue(Attribute, dwarf::DW_FORM_sec_offset, Value);
+  else
+    Die->addValue(Attribute, dwarf::DW_FORM_data4, Value);
 }
 
 /// addDIEEntry - Add a DIE attribute data and value.
@@ -1814,10 +1836,8 @@ DIE *CompileUnit::constructVariableDIE(DbgVariable &DV, bool isScopeAbstract) {
 
   unsigned Offset = DV.getDotDebugLocOffset();
   if (Offset != ~0U) {
-    addLabel(VariableDie, dwarf::DW_AT_location,
-             DD->getDwarfVersion() >= 4 ? dwarf::DW_FORM_sec_offset
-                                        : dwarf::DW_FORM_data4,
-             Asm->GetTempSymbol("debug_loc", Offset));
+    addSectionLabel(VariableDie, dwarf::DW_AT_location,
+                    Asm->GetTempSymbol("debug_loc", Offset));
     DV.setDIE(VariableDie);
     return VariableDie;
   }
diff --git a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
index 23d3afc024..0821a9a2b9 100644
--- a/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
+++ b/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
@@ -212,6 +212,14 @@ public:
 
   void addLabel(DIEBlock *Die, dwarf::Form Form, const MCSymbol *Label);
 
+  /// addSectionLabel - Add a Dwarf section label attribute data and value.
+  ///
+  void addSectionLabel(DIE *Die, dwarf::Attribute Attribute, const MCSymbol *Label);
+
+  /// addSectionOffset - Add an offset into a section attribute data and value.
+  ///
+  void addSectionOffset(DIE *Die, dwarf::Attribute Attribute, uint64_t Integer);
+
   /// addLabelAddress - Add a dwarf label attribute data and value using
   /// either DW_FORM_addr or DW_FORM_GNU_addr_index.
   void addLabelAddress(DIE *Die, dwarf::Attribute Attribute, MCSymbol *Label);
@@ -220,9 +228,9 @@ public:
   /// form given and an op of either DW_FORM_addr or DW_FORM_GNU_addr_index.
   void addOpAddress(DIEBlock *Die, const MCSymbol *Label);
 
-  /// addDelta - Add a label delta attribute data and value.
-  void addDelta(DIE *Die, dwarf::Attribute Attribute, dwarf::Form Form,
-                const MCSymbol *Hi, const MCSymbol *Lo);
+  /// addSectionDelta - Add a label delta attribute data and value.
+  void addSectionDelta(DIE *Die, dwarf::Attribute Attribute, const MCSymbol *Hi,
+                       const MCSymbol *Lo);
 
   /// addDIEEntry - Add a DIE attribute data and value.
   void addDIEEntry(DIE *Die, dwarf::Attribute Attribute, DIE *Entry);
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index d81e19c07a..6613aac87d 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -104,6 +104,11 @@ DwarfPubSections("generate-dwarf-pub-sections", cl::Hidden,
                             clEnumVal(Disable, "Disabled"), clEnumValEnd),
                  cl::init(Default));
 
+static cl::opt<unsigned>
+DwarfVersionNumber("dwarf-version", cl::Hidden,
+                   cl::desc("Generate DWARF for dwarf version."),
+                   cl::init(0));
+
 static const char *const DWARFGroupName = "DWARF Emission";
 static const char *const DbgTimerName = "DWARF Debug Writer";
 
@@ -212,7 +217,9 @@ DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
   else
     HasDwarfPubSections = DwarfPubSections == Enable;
 
-  DwarfVersion = getDwarfVersionFromModule(MMI->getModule());
+  DwarfVersion = DwarfVersionNumber
+                     ? DwarfVersionNumber
+                     : getDwarfVersionFromModule(MMI->getModule());
 
   {
     NamedRegionTimer T(DbgTimerName, DWARFGroupName, TimePassesIsEnabled);
@@ -470,9 +477,9 @@ DIE *DwarfDebug::constructLexicalScopeDIE(CompileUnit *TheCU,
     // .debug_range section has not been laid out yet. Emit offset in
     // .debug_range as a uint, size 4, for now. emitDIE will handle
     // DW_AT_ranges appropriately.
-    TheCU->addUInt(ScopeDIE, dwarf::DW_AT_ranges, dwarf::DW_FORM_data4,
-                   DebugRangeSymbols.size() *
-                       Asm->getDataLayout().getPointerSize());
+    TheCU->addSectionOffset(ScopeDIE, dwarf::DW_AT_ranges,
+                            DebugRangeSymbols.size() *
+                                Asm->getDataLayout().getPointerSize());
     for (SmallVectorImpl<InsnRange>::const_iterator RI = Ranges.begin(),
                                                     RE = Ranges.end();
          RI != RE; ++RI) {
@@ -526,9 +533,9 @@ DIE *DwarfDebug::constructInlinedScopeDIE(CompileUnit *TheCU,
     // .debug_range section has not been laid out yet. Emit offset in
     // .debug_range as a uint, size 4, for now. emitDIE will handle
     // DW_AT_ranges appropriately.
-    TheCU->addUInt(ScopeDIE, dwarf::DW_AT_ranges, dwarf::DW_FORM_data4,
-                   DebugRangeSymbols.size() *
-                       Asm->getDataLayout().getPointerSize());
+    TheCU->addSectionOffset(ScopeDIE, dwarf::DW_AT_ranges,
+                            DebugRangeSymbols.size() *
+                                Asm->getDataLayout().getPointerSize());
     for (SmallVectorImpl<InsnRange>::const_iterator RI = Ranges.begin(),
                                                     RE = Ranges.end();
          RI != RE; ++RI) {
@@ -766,14 +773,15 @@ CompileUnit *DwarfDebug::constructCompileUnit(DICompileUnit DIUnit) {
     // The line table entries are not always emitted in assembly, so it
     // is not okay to use line_table_start here.
     if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-      NewCU->addLabel(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_sec_offset,
-                      UseTheFirstCU ? Asm->GetTempSymbol("section_line")
-                                    : LineTableStartSym);
+      NewCU->addSectionLabel(
+          Die, dwarf::DW_AT_stmt_list,
+          UseTheFirstCU ? Asm->GetTempSymbol("section_line")
+                        : LineTableStartSym);
     else if (UseTheFirstCU)
-      NewCU->addUInt(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4, 0);
+      NewCU->addSectionOffset(Die, dwarf::DW_AT_stmt_list, 0);
     else
-      NewCU->addDelta(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4,
-                      LineTableStartSym, DwarfLineSectionSym);
+      NewCU->addSectionDelta(Die, dwarf::DW_AT_stmt_list,
+                             LineTableStartSym, DwarfLineSectionSym);
 
     // If we're using split dwarf the compilation dir is going to be in the
     // skeleton CU and so we don't need to duplicate it here.
@@ -784,22 +792,22 @@ CompileUnit *DwarfDebug::constructCompileUnit(DICompileUnit DIUnit) {
     // emit it here if we don't have a skeleton CU for split dwarf.
     if (GenerateGnuPubSections) {
       if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-        NewCU->addLabel(
-            Die, dwarf::DW_AT_GNU_pubnames, dwarf::DW_FORM_sec_offset,
+        NewCU->addSectionLabel(
+            Die, dwarf::DW_AT_GNU_pubnames,
             Asm->GetTempSymbol("gnu_pubnames", NewCU->getUniqueID()));
       else
-        NewCU->addDelta(
-            Die, dwarf::DW_AT_GNU_pubnames, dwarf::DW_FORM_data4,
+        NewCU->addSectionDelta(
+            Die, dwarf::DW_AT_GNU_pubnames,
             Asm->GetTempSymbol("gnu_pubnames", NewCU->getUniqueID()),
             DwarfGnuPubNamesSectionSym);
 
       if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-        NewCU->addLabel(
-            Die, dwarf::DW_AT_GNU_pubtypes, dwarf::DW_FORM_sec_offset,
+        NewCU->addSectionLabel(
+            Die, dwarf::DW_AT_GNU_pubtypes,
             Asm->GetTempSymbol("gnu_pubtypes", NewCU->getUniqueID()));
       else
-        NewCU->addDelta(
-            Die, dwarf::DW_AT_GNU_pubtypes, dwarf::DW_FORM_data4,
+        NewCU->addSectionDelta(
+            Die, dwarf::DW_AT_GNU_pubtypes,
             Asm->GetTempSymbol("gnu_pubtypes", NewCU->getUniqueID()),
             DwarfGnuPubTypesSectionSym);
     }
@@ -2957,11 +2965,10 @@ CompileUnit *DwarfDebug::constructSkeletonCU(const CompileUnit *CU) {
   // Relocate to the beginning of the addr_base section, else 0 for the
   // beginning of the one for this compile unit.
   if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-    NewCU->addLabel(Die, dwarf::DW_AT_GNU_addr_base, dwarf::DW_FORM_sec_offset,
-                    DwarfAddrSectionSym);
+    NewCU->addSectionLabel(Die, dwarf::DW_AT_GNU_addr_base,
+                           DwarfAddrSectionSym);
   else
-    NewCU->addUInt(Die, dwarf::DW_AT_GNU_addr_base, dwarf::DW_FORM_sec_offset,
-                   0);
+    NewCU->addSectionOffset(Die, dwarf::DW_AT_GNU_addr_base, 0);
 
   // 2.17.1 requires that we use DW_AT_low_pc for a single entry point
   // into an entity. We're using 0, or a NULL label for this.
@@ -2971,10 +2978,10 @@ CompileUnit *DwarfDebug::constructSkeletonCU(const CompileUnit *CU) {
   // compile unit in debug_line section.
   // FIXME: Should handle multiple compile units.
   if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-    NewCU->addLabel(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_sec_offset,
-                    DwarfLineSectionSym);
+    NewCU->addSectionLabel(Die, dwarf::DW_AT_stmt_list,
+                           DwarfLineSectionSym);
   else
-    NewCU->addUInt(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_sec_offset, 0);
+    NewCU->addSectionOffset(Die, dwarf::DW_AT_stmt_list, 0);
 
   if (!CompilationDir.empty())
     NewCU->addLocalString(Die, dwarf::DW_AT_comp_dir, CompilationDir);
@@ -2982,27 +2989,31 @@ CompileUnit *DwarfDebug::constructSkeletonCU(const CompileUnit *CU) {
   // Flags to let the linker know we have emitted new style pubnames.
   if (GenerateGnuPubSections) {
     if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-      NewCU->addLabel(Die, dwarf::DW_AT_GNU_pubnames, dwarf::DW_FORM_sec_offset,
-                      Asm->GetTempSymbol("gnu_pubnames", NewCU->getUniqueID()));
+      NewCU->addSectionLabel(
+          Die, dwarf::DW_AT_GNU_pubnames,
+          Asm->GetTempSymbol("gnu_pubnames", NewCU->getUniqueID()));
     else
-      NewCU->addDelta(Die, dwarf::DW_AT_GNU_pubnames, dwarf::DW_FORM_data4,
-                      Asm->GetTempSymbol("gnu_pubnames", NewCU->getUniqueID()),
-                      DwarfGnuPubNamesSectionSym);
+      NewCU->addSectionDelta(
+          Die, dwarf::DW_AT_GNU_pubnames,
+          Asm->GetTempSymbol("gnu_pubnames", NewCU->getUniqueID()),
+          DwarfGnuPubNamesSectionSym);
 
     if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-      NewCU->addLabel(Die, dwarf::DW_AT_GNU_pubtypes, dwarf::DW_FORM_sec_offset,
-                      Asm->GetTempSymbol("gnu_pubtypes", NewCU->getUniqueID()));
+      NewCU->addSectionLabel(
+          Die, dwarf::DW_AT_GNU_pubtypes,
+          Asm->GetTempSymbol("gnu_pubtypes", NewCU->getUniqueID()));
     else
-      NewCU->addDelta(Die, dwarf::DW_AT_GNU_pubtypes, dwarf::DW_FORM_data4,
-                      Asm->GetTempSymbol("gnu_pubtypes", NewCU->getUniqueID()),
-                      DwarfGnuPubTypesSectionSym);
+      NewCU->addSectionDelta(
+          Die, dwarf::DW_AT_GNU_pubtypes,
+          Asm->GetTempSymbol("gnu_pubtypes", NewCU->getUniqueID()),
+          DwarfGnuPubTypesSectionSym);
   }
 
   // Flag if we've emitted any ranges and their location for the compile unit.
   if (DebugRangeSymbols.size()) {
     if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
-      NewCU->addLabel(Die, dwarf::DW_AT_GNU_ranges_base,
-                      dwarf::DW_FORM_sec_offset, DwarfDebugRangeSectionSym);
+      NewCU->addSectionLabel(Die, dwarf::DW_AT_GNU_ranges_base,
+                             DwarfDebugRangeSectionSym);
     else
       NewCU->addUInt(Die, dwarf::DW_AT_GNU_ranges_base, dwarf::DW_FORM_data4,
                      0);