[Lldb-commits] [lldb] r179431 - Handle an edge case where we step into a function whose UnwindPlan

[Jason Molenda]

Author: jmolenda
Date: Fri Apr 12 19:29:13 2013
New Revision: 179431

URL: http://llvm.org/viewvc/llvm-project?rev=179431&view=rev
Log:
Handle an edge case where we step into a function whose UnwindPlan
defines a Return Address register (e.g. lr on arm) but the RA register
hasn't been saved anywhere yet -- it is still in a live reg.
<rdar://problem/13503130> 

Modified:
    lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp

Modified: lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp?rev=179431&r1=179430&r2=179431&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp (original)
+++ lldb/trunk/source/Plugins/Process/Utility/RegisterContextLLDB.cpp Fri Apr 12 19:29:13 2013
@@ -978,12 +978,14 @@ RegisterContextLLDB::SavedLocationForReg
             UnwindPlan::RowSP active_row = m_full_unwind_plan_sp->GetRowForFunctionOffset (m_current_offset);
             unwindplan_registerkind = m_full_unwind_plan_sp->GetRegisterKind ();
             uint32_t row_regnum;
+            bool row_register_rewritten_to_return_address_reg = false;
 
             // If we're fetching the saved pc and this UnwindPlan defines a ReturnAddress register (e.g. lr on arm),
             // look for the return address register number in the UnwindPlan's row.
             if (lldb_regnum == pc_regnum && m_full_unwind_plan_sp->GetReturnAddressRegister() != LLDB_INVALID_REGNUM)
             {
                row_regnum = m_full_unwind_plan_sp->GetReturnAddressRegister();
+               row_register_rewritten_to_return_address_reg = true;
                UnwindLogMsg ("requested caller's saved PC but this UnwindPlan uses a RA reg; getting reg %d instead",
                        row_regnum);
             }
@@ -1007,6 +1009,28 @@ RegisterContextLLDB::SavedLocationForReg
                               m_full_unwind_plan_sp->GetSourceName().GetCString());
             }
 
+            // This is frame 0 and we're retrieving the PC and it's saved in a Return Address register and
+            // it hasn't been saved anywhere yet -- that is, it's still live in the actual register.
+            // Handle this specially.
+
+            if (have_unwindplan_regloc == false 
+                && row_register_rewritten_to_return_address_reg == true 
+                && IsFrameZero()
+                && row_regnum != LLDB_INVALID_REGNUM)
+            {
+                uint32_t ra_regnum_in_lldb_reg_numbering;
+                if (m_thread.GetRegisterContext()->ConvertBetweenRegisterKinds (unwindplan_registerkind, row_regnum, eRegisterKindLLDB, ra_regnum_in_lldb_reg_numbering))
+                {
+                    lldb_private::UnwindLLDB::RegisterLocation new_regloc;
+                    new_regloc.type = UnwindLLDB::RegisterLocation::eRegisterInRegister;
+                    new_regloc.location.register_number = ra_regnum_in_lldb_reg_numbering;
+                    m_registers[lldb_regnum] = new_regloc;
+                    regloc = new_regloc;
+                    UnwindLogMsg ("supplying caller's register %d from the live RegisterContext at frame 0, saved in %d", lldb_regnum, ra_regnum_in_lldb_reg_numbering);
+                    return UnwindLLDB::RegisterSearchResult::eRegisterFound;
+                }
+            }
+
             // If this architecture stores the return address in a register (it defines a Return Address register)
             // and we're on a non-zero stack frame and the Full UnwindPlan says that the pc is stored in the
             // RA registers (e.g. lr on arm), then we know that the full unwindplan is not trustworthy -- this