[lldb] Support negative function offsets in UnwindPlans

These are needed for functions whose entry point is not their lowest
address.

Author: labath

lldb/include/lldb/Symbol/UnwindPlan.h

@@ -356,11 +356,11 @@ class UnwindPlan {
 
     void RemoveRegisterInfo(uint32_t reg_num);
 
-    lldb::addr_t GetOffset() const { return m_offset; }
+    int64_t GetOffset() const { return m_offset; }
 
-    void SetOffset(lldb::addr_t offset) { m_offset = offset; }
+    void SetOffset(int64_t offset) { m_offset = offset; }
 
-    void SlideOffset(lldb::addr_t offset) { m_offset += offset; }
+    void SlideOffset(int64_t offset) { m_offset += offset; }
 
     const FAValue &GetCFAValue() const { return m_cfa_value; }
     FAValue &GetCFAValue() { return m_cfa_value; }
@@ -420,7 +420,7 @@ class UnwindPlan {
 
   protected:
     typedef std::map<uint32_t, AbstractRegisterLocation> collection;
-    lldb::addr_t m_offset = 0; // Offset into the function for this row
+    int64_t m_offset = 0; // Offset into the function for this row
 
     FAValue m_cfa_value;
     FAValue m_afa_value;
@@ -455,7 +455,7 @@ class UnwindPlan {
   // practice, the UnwindPlan for a function with no known start address will be
   // the architectural default UnwindPlan which will only have one row.
   const UnwindPlan::Row *
-  GetRowForFunctionOffset(std::optional<int> offset) const;
+  GetRowForFunctionOffset(std::optional<int64_t> offset) const;
 
   lldb::RegisterKind GetRegisterKind() const { return m_register_kind; }
 

lldb/source/Plugins/UnwindAssembly/x86/x86AssemblyInspectionEngine.cpp

@@ -1390,11 +1390,12 @@ bool x86AssemblyInspectionEngine::AugmentUnwindPlanFromCallSite(
 
     // If we already have one row for this instruction, we can continue.
     while (row_id < unwind_plan.GetRowCount() &&
-           unwind_plan.GetRowAtIndex(row_id)->GetOffset() <= offset) {
+           unwind_plan.GetRowAtIndex(row_id)->GetOffset() <=
+               static_cast<int64_t>(offset)) {
       row_id++;
     }
     const UnwindPlan::Row *original_row = unwind_plan.GetRowAtIndex(row_id - 1);
-    if (original_row->GetOffset() == offset) {
+    if (original_row->GetOffset() == static_cast<int64_t>(offset)) {
       row = *original_row;
       continue;
     }

lldb/source/Symbol/DWARFCallFrameInfo.cpp

@@ -765,7 +765,7 @@ bool DWARFCallFrameInfo::FDEToUnwindPlan(dw_offset_t dwarf_offset,
                      __FUNCTION__, dwarf_offset, startaddr.GetFileAddress());
             break;
           }
-          lldb::addr_t offset = row.GetOffset();
+          int64_t offset = row.GetOffset();
           row = std::move(stack.back());
           stack.pop_back();
           row.SetOffset(offset);

lldb/source/Symbol/UnwindPlan.cpp

@@ -398,10 +398,10 @@ void UnwindPlan::AppendRow(Row row) {
 }
 
 struct RowLess {
-  bool operator()(addr_t a, const UnwindPlan::Row &b) const {
+  bool operator()(int64_t a, const UnwindPlan::Row &b) const {
     return a < b.GetOffset();
   }
-  bool operator()(const UnwindPlan::Row &a, addr_t b) const {
+  bool operator()(const UnwindPlan::Row &a, int64_t b) const {
     return a.GetOffset() < b;
   }
 };
@@ -418,7 +418,7 @@ void UnwindPlan::InsertRow(Row row, bool replace_existing) {
 }
 
 const UnwindPlan::Row *
-UnwindPlan::GetRowForFunctionOffset(std::optional<int> offset) const {
+UnwindPlan::GetRowForFunctionOffset(std::optional<int64_t> offset) const {
   auto it = offset ? llvm::upper_bound(m_row_list, *offset, RowLess())
                    : m_row_list.end();
   if (it == m_row_list.begin())

lldb/unittests/Symbol/UnwindPlanTest.cpp

@@ -24,6 +24,7 @@ static UnwindPlan::Row make_simple_row(addr_t offset, uint64_t cfa_value) {
 TEST(UnwindPlan, InsertRow) {
   UnwindPlan::Row row1 = make_simple_row(0, 42);
   UnwindPlan::Row row2 = make_simple_row(0, 47);
+  UnwindPlan::Row row3 = make_simple_row(-1, 4242);
 
   UnwindPlan plan(eRegisterKindGeneric);
   plan.InsertRow(row1);
@@ -34,6 +35,10 @@ TEST(UnwindPlan, InsertRow) {
 
   plan.InsertRow(row2, /*replace_existing=*/true);
   EXPECT_THAT(plan.GetRowForFunctionOffset(0), testing::Pointee(row2));
+
+  EXPECT_THAT(plan.GetRowForFunctionOffset(-1), nullptr);
+  plan.InsertRow(row3);
+  EXPECT_THAT(plan.GetRowForFunctionOffset(-1), testing::Pointee(row3));
 }
 
 TEST(UnwindPlan, GetRowForFunctionOffset) {