[lldb][nfc] Initialize m_initial_sp in ctor for UnwindAssemblyInstEmulation (#167914)

Also rename the "sp" suffix (originally intended to mean "Stack
Pointer") to "cfa", as "sp" generally means Shared Pointer.

Author: felipepiovezan

lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp

@@ -109,21 +109,15 @@ bool UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly(
   m_range_ptr = ⦥
   m_unwind_plan_ptr = &unwind_plan;
 
-  const uint32_t addr_byte_size = m_arch.GetAddressByteSize();
-
   m_state.cfa_reg_info = *m_inst_emulator_up->GetRegisterInfo(
       unwind_plan.GetRegisterKind(), unwind_plan.GetInitialCFARegister());
   m_state.fp_is_cfa = false;
   m_state.register_values.clear();
 
   m_pushed_regs.clear();
 
-  // Initialize the CFA with a known value. In the 32 bit case it will be
-  // 0x80000000, and in the 64 bit case 0x8000000000000000. We use the address
-  // byte size to be safe for any future address sizes
-  m_initial_sp = (1ull << ((addr_byte_size * 8) - 1));
   RegisterValue cfa_reg_value;
-  cfa_reg_value.SetUInt(m_initial_sp, m_state.cfa_reg_info.byte_size);
+  cfa_reg_value.SetUInt(m_initial_cfa, m_state.cfa_reg_info.byte_size);
   SetRegisterValue(m_state.cfa_reg_info, cfa_reg_value);
 
   const InstructionList &inst_list = disasm_sp->GetInstructionList();
@@ -392,7 +386,7 @@ size_t UnwindAssemblyInstEmulation::WriteMemory(
     if (reg_num != LLDB_INVALID_REGNUM &&
         generic_regnum != LLDB_REGNUM_GENERIC_SP) {
       if (m_pushed_regs.try_emplace(reg_num, addr).second) {
-        const int32_t offset = addr - m_initial_sp;
+        const int32_t offset = addr - m_initial_cfa;
         m_state.row.SetRegisterLocationToAtCFAPlusOffset(reg_num, offset,
                                                          /*can_replace=*/true);
         m_curr_row_modified = true;
@@ -559,7 +553,7 @@ bool UnwindAssemblyInstEmulation::WriteRegister(
                   sp_reg_info.kinds[m_unwind_plan_ptr->GetRegisterKind()];
               assert(cfa_reg_num != LLDB_INVALID_REGNUM);
               m_state.row.GetCFAValue().SetIsRegisterPlusOffset(
-                  cfa_reg_num, m_initial_sp - sp_reg_val.GetAsUInt64());
+                  cfa_reg_num, m_initial_cfa - sp_reg_val.GetAsUInt64());
             }
           }
         }
@@ -590,7 +584,7 @@ bool UnwindAssemblyInstEmulation::WriteRegister(
           reg_info->kinds[m_unwind_plan_ptr->GetRegisterKind()];
       assert(cfa_reg_num != LLDB_INVALID_REGNUM);
       m_state.row.GetCFAValue().SetIsRegisterPlusOffset(
-          cfa_reg_num, m_initial_sp - reg_value.GetAsUInt64());
+          cfa_reg_num, m_initial_cfa - reg_value.GetAsUInt64());
       m_curr_row_modified = true;
     }
     break;
@@ -603,7 +597,7 @@ bool UnwindAssemblyInstEmulation::WriteRegister(
           reg_info->kinds[m_unwind_plan_ptr->GetRegisterKind()];
       assert(cfa_reg_num != LLDB_INVALID_REGNUM);
       m_state.row.GetCFAValue().SetIsRegisterPlusOffset(
-          cfa_reg_num, m_initial_sp - reg_value.GetAsUInt64());
+          cfa_reg_num, m_initial_cfa - reg_value.GetAsUInt64());
       m_curr_row_modified = true;
     }
     break;
@@ -614,7 +608,7 @@ bool UnwindAssemblyInstEmulation::WriteRegister(
     if (!m_state.fp_is_cfa) {
       m_state.row.GetCFAValue().SetIsRegisterPlusOffset(
           m_state.row.GetCFAValue().GetRegisterNumber(),
-          m_initial_sp - reg_value.GetAsUInt64());
+          m_initial_cfa - reg_value.GetAsUInt64());
       m_curr_row_modified = true;
     }
     break;

lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.h

@@ -63,13 +63,17 @@ class UnwindAssemblyInstEmulation : public lldb_private::UnwindAssembly {
   UnwindAssemblyInstEmulation(const lldb_private::ArchSpec &arch,
                               lldb_private::EmulateInstruction *inst_emulator)
       : UnwindAssembly(arch), m_inst_emulator_up(inst_emulator),
-        m_range_ptr(nullptr), m_unwind_plan_ptr(nullptr), m_initial_sp(0),
+        m_range_ptr(nullptr), m_unwind_plan_ptr(nullptr),
         m_curr_row_modified(false), m_forward_branch_offset(0) {
     if (m_inst_emulator_up) {
       m_inst_emulator_up->SetBaton(this);
       m_inst_emulator_up->SetCallbacks(ReadMemory, WriteMemory, ReadRegister,
                                        WriteRegister);
     }
+    // Initialize the CFA with a known value. In the 32 bit case it will be
+    // 0x80000000, and in the 64 bit case 0x8000000000000000. We use the address
+    // byte size to be safe for any future address sizes
+    m_initial_cfa = (1ull << ((m_arch.GetAddressByteSize() * 8) - 1));
   }
 
   static size_t
@@ -134,8 +138,8 @@ class UnwindAssemblyInstEmulation : public lldb_private::UnwindAssembly {
   lldb_private::AddressRange *m_range_ptr;
   lldb_private::UnwindPlan *m_unwind_plan_ptr;
   UnwindState m_state;
+  uint64_t m_initial_cfa;
   typedef std::map<uint64_t, uint64_t> PushedRegisterToAddrMap;
-  uint64_t m_initial_sp;
   PushedRegisterToAddrMap m_pushed_regs;
 
   // While processing the instruction stream, we need to communicate some state