DWARF: Implement DW_AT_signature lookup for type unit support

Summary:
This patch implements the main feature of type units. When completing a
type, if we encounter a DW_AT_signature attribute, we use it's value to
lookup the complete definition of the type in the relevant type unit.

To enable this lookup, we build up a map of all type units in a symbol
file when parsing the units. Then we consult this map when resolving the
DW_AT_signature attribute.

I include add a couple of tests which exercise the type lookup feature,
including one that ensure we do something reasonable in case we fail to
lookup the type.

A lot of the ideas in this patch have been taken from D32167 and D61505.

Reviewers: clayborg, JDevlieghere, aprantl, alexshap

Subscribers: mgrang, lldb-commits

Differential Revision: https://reviews.llvm.org/D62246

llvm-svn: 361603

1 files changed, 24 insertions, 11 deletions

diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
index c81b6ce05f0f..0810afc8b1a1 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFDebugInfo.cpp
@@ -15,6 +15,7 @@
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Utility/RegularExpression.h"
 #include "lldb/Utility/Stream.h"
+#include "llvm/Support/Casting.h"
 
 #include "DWARFCompileUnit.h"
 #include "DWARFContext.h"
@@ -74,12 +75,14 @@ llvm::Expected<DWARFDebugAranges &> DWARFDebugInfo::GetCompileUnitAranges() {
   return *m_cu_aranges_up;
 }
 
-void Parse(SymbolFileDWARF *dwarf, const DWARFDataExtractor &data,
-           DIERef::Section section, std::vector<DWARFUnitSP> &units) {
+void DWARFDebugInfo::ParseUnitsFor(DIERef::Section section) {
+  DWARFDataExtractor data = section == DIERef::Section::DebugTypes
+                                ? m_context.getOrLoadDebugTypesData()
+                                : m_context.getOrLoadDebugInfoData();
   lldb::offset_t offset = 0;
   while (data.ValidOffset(offset)) {
-    llvm::Expected<DWARFUnitSP> unit_sp =
-        DWARFUnit::extract(dwarf, units.size(), data, section, &offset);
+    llvm::Expected<DWARFUnitSP> unit_sp = DWARFUnit::extract(
+        m_dwarf2Data, m_units.size(), data, section, &offset);
 
     if (!unit_sp) {
       // FIXME: Propagate this error up.
@@ -89,10 +92,13 @@ void Parse(SymbolFileDWARF *dwarf, const DWARFDataExtractor &data,
 
     // If it didn't return an error, then it should be returning a valid Unit.
     assert(*unit_sp);
-
-    units.push_back(*unit_sp);
-
+    m_units.push_back(*unit_sp);
     offset = (*unit_sp)->GetNextUnitOffset();
+
+    if (auto *type_unit = llvm::dyn_cast<DWARFTypeUnit>(unit_sp->get())) {
+      m_type_hash_to_unit_index.emplace_back(type_unit->GetTypeHash(),
+                                             unit_sp.get()->GetID());
+    }
   }
 }
 
@@ -102,10 +108,9 @@ void DWARFDebugInfo::ParseUnitHeadersIfNeeded() {
   if (!m_dwarf2Data)
     return;
 
-  Parse(m_dwarf2Data, m_context.getOrLoadDebugInfoData(),
-        DIERef::Section::DebugInfo, m_units);
-  Parse(m_dwarf2Data, m_context.getOrLoadDebugTypesData(),
-        DIERef::Section::DebugTypes, m_units);
+  ParseUnitsFor(DIERef::Section::DebugInfo);
+  ParseUnitsFor(DIERef::Section::DebugTypes);
+  llvm::sort(m_type_hash_to_unit_index, llvm::less_first());
 }
 
 size_t DWARFDebugInfo::GetNumUnits() {
@@ -169,6 +174,14 @@ DWARFDebugInfo::GetUnitContainingDIEOffset(DIERef::Section section,
   return result;
 }
 
+DWARFTypeUnit *DWARFDebugInfo::GetTypeUnitForHash(uint64_t hash) {
+  auto pos = llvm::lower_bound(m_type_hash_to_unit_index,
+                               std::make_pair(hash, 0u), llvm::less_first());
+  if (pos == m_type_hash_to_unit_index.end() || pos->first != hash)
+    return nullptr;
+  return llvm::cast<DWARFTypeUnit>(GetUnitAtIndex(pos->second));
+}
+
 DWARFDIE
 DWARFDebugInfo::GetDIEForDIEOffset(DIERef::Section section,
                                    dw_offset_t die_offset) {