[lldb] Teach FuncUnwinders about discontinuous functions

lldb/include/lldb/Symbol/FuncUnwinders.h

@@ -13,9 +13,9 @@ class UnwindTable;
 class FuncUnwinders {
 public:
   // FuncUnwinders objects are used to track UnwindPlans for a function (named
-  // or not - really just an address range)
+  // or not - really just a set of address ranges)
 
-  // We'll record four different UnwindPlans for each address range:
+  // We'll record four different UnwindPlans for each function:
   //
   //   1. Unwinding from a call site (a valid exception throw location)
   //      This is often sourced from the eh_frame exception handling info
@@ -31,7 +31,8 @@ class FuncUnwinders {
   // instructions are finished for migrating breakpoints past the stack frame
   // setup instructions when we don't have line table information.
 
-  FuncUnwinders(lldb_private::UnwindTable &unwind_table, AddressRange range);
+  FuncUnwinders(lldb_private::UnwindTable &unwind_table, Address addr,
+                AddressRanges ranges);
 
   ~FuncUnwinders();
 
@@ -54,7 +55,9 @@ class FuncUnwinders {
   const Address &GetFunctionStartAddress() const;
 
   bool ContainsAddress(const Address &addr) const {
-    return m_range.ContainsFileAddress(addr);
+    return llvm::any_of(m_ranges, [&](const AddressRange range) {
+      return range.ContainsFileAddress(addr);
+    });
   }
 
   // A function may have a Language Specific Data Area specified -- a block of
@@ -113,6 +116,15 @@ class FuncUnwinders {
       Thread &thread, const lldb::UnwindPlanSP &a, const lldb::UnwindPlanSP &b);
 
   UnwindTable &m_unwind_table;
+
+  /// Start address of the function described by this object.
+  Address m_addr;
+
+  /// The address ranges of the function.
+  AddressRanges m_ranges;
+
+  /// The smallest address range covering the entire function.
+  /// DEPRECATED: Use m_ranges instead.
   AddressRange m_range;
 
   std::recursive_mutex m_mutex;

lldb/include/lldb/Symbol/UnwindTable.h

@@ -66,8 +66,7 @@ class UnwindTable {
   void Dump(Stream &s);
 
   void Initialize();
-  std::optional<AddressRange> GetAddressRange(const Address &addr,
-                                              const SymbolContext &sc);
+  AddressRanges GetAddressRanges(const Address &addr, const SymbolContext &sc);
 
   typedef std::map<lldb::addr_t, lldb::FuncUnwindersSP> collection;
   typedef collection::iterator iterator;

lldb/source/Symbol/FuncUnwinders.cpp

@@ -31,15 +31,29 @@
 using namespace lldb;
 using namespace lldb_private;
 
-/// constructor
-
-FuncUnwinders::FuncUnwinders(UnwindTable &unwind_table, AddressRange range)
-    : m_unwind_table(unwind_table), m_range(range), m_mutex(),
-      m_unwind_plan_assembly_sp(), m_unwind_plan_eh_frame_sp(),
-      m_unwind_plan_eh_frame_augmented_sp(), m_unwind_plan_compact_unwind(),
-      m_unwind_plan_arm_unwind_sp(), m_unwind_plan_fast_sp(),
-      m_unwind_plan_arch_default_sp(),
-      m_unwind_plan_arch_default_at_func_entry_sp(),
+static AddressRange CollapseRanges(llvm::ArrayRef<AddressRange> ranges) {
+  if (ranges.empty())
+    return AddressRange();
+  if (ranges.size() == 1)
+    return ranges[0];
+
+  Address lowest_addr = ranges[0].GetBaseAddress();
+  addr_t highest_addr = lowest_addr.GetFileAddress() + ranges[0].GetByteSize();
+  for (const AddressRange &range : ranges.drop_front()) {
+    Address range_begin = range.GetBaseAddress();
+    addr_t range_end = range_begin.GetFileAddress() + range.GetByteSize();
+    if (range_begin.GetFileAddress() < lowest_addr.GetFileAddress())
+      lowest_addr = range_begin;
+    if (range_end > highest_addr)
+      highest_addr = range_end;
+  }
+  return AddressRange(lowest_addr, highest_addr - lowest_addr.GetFileAddress());
+}
+
+FuncUnwinders::FuncUnwinders(UnwindTable &unwind_table, Address addr,
+                             AddressRanges ranges)
+    : m_unwind_table(unwind_table), m_addr(std::move(addr)),
+      m_ranges(std::move(ranges)), m_range(CollapseRanges(m_ranges)),
       m_tried_unwind_plan_assembly(false), m_tried_unwind_plan_eh_frame(false),
       m_tried_unwind_plan_object_file(false),
       m_tried_unwind_plan_debug_frame(false),
@@ -511,9 +525,7 @@ Address &FuncUnwinders::GetFirstNonPrologueInsn(Target &target) {
   return m_first_non_prologue_insn;
 }
 
-const Address &FuncUnwinders::GetFunctionStartAddress() const {
-  return m_range.GetBaseAddress();
-}
+const Address &FuncUnwinders::GetFunctionStartAddress() const { return m_addr; }
 
 lldb::UnwindAssemblySP
 FuncUnwinders::GetUnwindAssemblyProfiler(Target &target) {

lldb/source/Symbol/UnwindTable.cpp

@@ -91,30 +91,35 @@ void UnwindTable::ModuleWasUpdated() {
 
 UnwindTable::~UnwindTable() = default;
 
-std::optional<AddressRange>
-UnwindTable::GetAddressRange(const Address &addr, const SymbolContext &sc) {
+AddressRanges UnwindTable::GetAddressRanges(const Address &addr,
+                                            const SymbolContext &sc) {
   AddressRange range;
 
   // First check the unwind info from the object file plugin
   if (m_object_file_unwind_up &&
       m_object_file_unwind_up->GetAddressRange(addr, range))
-    return range;
+    return {range};
 
   // Check the symbol context
-  if (sc.GetAddressRange(eSymbolContextFunction | eSymbolContextSymbol, 0,
-                         false, range) &&
-      range.GetBaseAddress().IsValid())
-    return range;
+  AddressRanges result;
+  for (size_t idx = 0;
+       sc.GetAddressRange(eSymbolContextFunction | eSymbolContextSymbol, idx,
+                          false, range) &&
+       range.GetBaseAddress().IsValid();
+       ++idx)
+    result.push_back(range);
+  if (!result.empty())
+    return result;
 
   // Does the eh_frame unwind info has a function bounds for this addr?
   if (m_eh_frame_up && m_eh_frame_up->GetAddressRange(addr, range))
-    return range;
+    return {range};
 
   // Try debug_frame as well
   if (m_debug_frame_up && m_debug_frame_up->GetAddressRange(addr, range))
-    return range;
+    return {range};
 
-  return std::nullopt;
+  return {};
 }
 
 FuncUnwindersSP
@@ -140,14 +145,14 @@ UnwindTable::GetFuncUnwindersContainingAddress(const Address &addr,
       return pos->second;
   }
 
-  auto range_or = GetAddressRange(addr, sc);
-  if (!range_or)
+  AddressRanges ranges = GetAddressRanges(addr, sc);
+  if (ranges.empty())
     return nullptr;
 
-  FuncUnwindersSP func_unwinder_sp(new FuncUnwinders(*this, *range_or));
-  m_unwinds.insert(insert_pos,
-                   std::make_pair(range_or->GetBaseAddress().GetFileAddress(),
-                                  func_unwinder_sp));
+  auto func_unwinder_sp = std::make_shared<FuncUnwinders>(*this, addr, ranges);
+  for (const AddressRange &range : ranges)
+    m_unwinds.emplace_hint(insert_pos, range.GetBaseAddress().GetFileAddress(),
+                           func_unwinder_sp);
   return func_unwinder_sp;
 }
 
@@ -159,11 +164,11 @@ FuncUnwindersSP UnwindTable::GetUncachedFuncUnwindersContainingAddress(
     const Address &addr, const SymbolContext &sc) {
   Initialize();
 
-  auto range_or = GetAddressRange(addr, sc);
-  if (!range_or)
+  AddressRanges ranges = GetAddressRanges(addr, sc);
+  if (ranges.empty())
     return nullptr;
 
-  return std::make_shared<FuncUnwinders>(*this, *range_or);
+  return std::make_shared<FuncUnwinders>(*this, addr, std::move(ranges));
 }
 
 void UnwindTable::Dump(Stream &s) {