[llvm-dwp] Emit a rather fictional debug_cu_index

This is very rudimentary support for debug_cu_index, but it is enough to
allow llvm-dwarfdump to find the offsets for  contributions and
correctly dump debug_info.

It will need to actually find the real signature of the unit and build
the real hash table with the right number of buckets, as per the DWP
specification.

It will also need to be expanded to cover the tu_index as well.

llvm-svn: 254489

3 files changed, 27 insertions, 13 deletions

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index 2165d353ba0..a4195b75c47 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -163,20 +163,12 @@ void DWARFContext::dump(raw_ostream &OS, DIDumpType DumpType) {
 
   if (DumpType == DIDT_All || DumpType == DIDT_CUIndex) {
     OS << "\n.debug_cu_index contents:\n";
-    DataExtractor CUIndexData(getCUIndexSection(), isLittleEndian(),
-                              savedAddressByteSize);
-    DWARFUnitIndex CUIndex;
-    if (CUIndex.parse(CUIndexData))
-      CUIndex.dump(OS);
+    getCUIndex().dump(OS);
   }
 
   if (DumpType == DIDT_All || DumpType == DIDT_TUIndex) {
     OS << "\n.debug_tu_index contents:\n";
-    DataExtractor TUIndexData(getTUIndexSection(), isLittleEndian(),
-                              savedAddressByteSize);
-    DWARFUnitIndex TUIndex;
-    if (TUIndex.parse(TUIndexData))
-      TUIndex.dump(OS);
+    getTUIndex().dump(OS);
   }
 
   if (DumpType == DIDT_All || DumpType == DIDT_LineDwo) {
@@ -280,7 +272,7 @@ const DWARFUnitIndex &DWARFContext::getCUIndex() {
 
   DataExtractor CUIndexData(getCUIndexSection(), isLittleEndian(), 0);
 
-  CUIndex = llvm::make_unique<DWARFUnitIndex>();
+  CUIndex = llvm::make_unique<DWARFUnitIndex>(DW_SECT_INFO);
   CUIndex->parse(CUIndexData);
   return *CUIndex;
 }
@@ -291,7 +283,7 @@ const DWARFUnitIndex &DWARFContext::getTUIndex() {
 
   DataExtractor TUIndexData(getTUIndexSection(), isLittleEndian(), 0);
 
-  TUIndex = llvm::make_unique<DWARFUnitIndex>();
+  TUIndex = llvm::make_unique<DWARFUnitIndex>(DW_SECT_TYPES);
   TUIndex->parse(TUIndexData);
   return *TUIndex;
 }
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp
index baefed30f36..e8e7441d976 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnitIndex.cpp
@@ -30,6 +30,13 @@ void DWARFUnitIndex::Header::dump(raw_ostream &OS) const {
 }
 
 bool DWARFUnitIndex::parse(DataExtractor IndexData) {
+  bool b = parseImpl(IndexData);
+  if (!b)
+    *this = DWARFUnitIndex(InfoColumnKind);
+  return b;
+}
+
+bool DWARFUnitIndex::parseImpl(DataExtractor IndexData) {
   uint32_t Offset = 0;
   if (!Header.parse(IndexData, &Offset))
     return false;
@@ -62,7 +69,7 @@ bool DWARFUnitIndex::parse(DataExtractor IndexData) {
   // Read the Column Headers
   for (unsigned i = 0; i != Header.NumColumns; ++i) {
     ColumnKinds[i] = static_cast<DWARFSectionKind>(IndexData.getU32(&Offset));
-    if (ColumnKinds[i] == DW_SECT_INFO || ColumnKinds[i] == DW_SECT_TYPES) {
+    if (ColumnKinds[i] == InfoColumnKind) {
       if (InfoColumn != -1)
         return false;
       InfoColumn = i;
@@ -107,6 +114,9 @@ StringRef DWARFUnitIndex::getColumnHeader(DWARFSectionKind DS) {
 }
 
 void DWARFUnitIndex::dump(raw_ostream &OS) const {
+  if (!Header.NumBuckets)
+    return;
+
   Header.dump(OS);
   OS << "Index Signature         ";
   for (unsigned i = 0; i != Header.NumColumns; ++i)
diff --git a/llvm/lib/MC/MCObjectFileInfo.cpp b/llvm/lib/MC/MCObjectFileInfo.cpp
index 8b75457a246..41e28698b1c 100644
--- a/llvm/lib/MC/MCObjectFileInfo.cpp
+++ b/llvm/lib/MC/MCObjectFileInfo.cpp
@@ -259,6 +259,9 @@ void MCObjectFileInfo::initMachOMCObjectFileInfo(Triple T) {
   DwarfDebugInlineSection =
       Ctx->getMachOSection("__DWARF", "__debug_inlined", MachO::S_ATTR_DEBUG,
                            SectionKind::getMetadata());
+  DwarfCUIndexSection =
+      Ctx->getMachOSection("__DWARF", "__debug_cu_index", MachO::S_ATTR_DEBUG,
+                           SectionKind::getMetadata());
   StackMapSection = Ctx->getMachOSection("__LLVM_STACKMAPS", "__llvm_stackmaps",
                                          0, SectionKind::getMetadata());
 
@@ -531,6 +534,10 @@ void MCObjectFileInfo::initELFMCObjectFileInfo(Triple T) {
   DwarfAddrSection =
       Ctx->getELFSection(".debug_addr", ELF::SHT_PROGBITS, 0, "addr_sec");
 
+  // DWP Sections
+  DwarfCUIndexSection =
+      Ctx->getELFSection(".debug_cu_index", ELF::SHT_PROGBITS, 0);
+
   StackMapSection =
       Ctx->getELFSection(".llvm_stackmaps", ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
 
@@ -713,6 +720,11 @@ void MCObjectFileInfo::initCOFFMCObjectFileInfo(Triple T) {
       COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
           COFF::IMAGE_SCN_MEM_READ,
       SectionKind::getMetadata(), "addr_sec");
+  DwarfCUIndexSection = Ctx->getCOFFSection(
+      ".debug_cu_index",
+      COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
+          COFF::IMAGE_SCN_MEM_READ,
+      SectionKind::getMetadata());
   DwarfAccelNamesSection = Ctx->getCOFFSection(
       ".apple_names",
       COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |