From 6e264d39dc0de26ea8bac28cdd23e2386ba2861a Mon Sep 17 00:00:00 2001
From: Ashok Thirumurthi <ashok.thirumurthi@intel.com>
Date: Mon, 29 Jul 2013 16:05:11 +0000
Subject: [PATCH] Adds a DW_OP_call_frame_cfa handler when evaluating DWARF 3/4
 expressions in LLDB that load the canonical frame address rather than a
 location list.

- Handles the simple case where a CFA can be pulled from the current stack frame.
- Fixes more than one hundred failing tests with gcc 4.8!

TODO: Use UnwindPlan::GetRowForFunctionOffset if the DWARFExpression needs
to be evaluated in a context analogous to a virtual unwind (perhaps using RegisterContextLLDB).

- Also adds some comments to DWARFCallFrameInfo whenever I got confused.

llvm-svn: 187361
---
 lldb/source/Expression/DWARFExpression.cpp | 32 ++++++++++++++++++++++++++++++
 lldb/source/Symbol/DWARFCallFrameInfo.cpp  |  3 ++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/lldb/source/Expression/DWARFExpression.cpp b/lldb/source/Expression/DWARFExpression.cpp
index 7797205..fc955c5 100644
--- a/lldb/source/Expression/DWARFExpression.cpp
+++ b/lldb/source/Expression/DWARFExpression.cpp
@@ -37,6 +37,7 @@
 #include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/StackFrame.h"
+#include "lldb/Target/StackID.h"
 
 using namespace lldb;
 using namespace lldb_private;
@@ -2627,6 +2628,37 @@ DWARFExpression::Evaluate
         case DW_OP_stack_value:
             stack.back().SetValueType(Value::eValueTypeScalar);
             break;
+
+        //----------------------------------------------------------------------
+        // OPCODE: DW_OP_call_frame_cfa
+        // OPERANDS: None
+        // DESCRIPTION: Specifies a DWARF expression that pushes the value of
+        // the canonical frame address consistent with the call frame information
+        // located in .debug_frame (or in the FDEs of the eh_frame section).
+        //----------------------------------------------------------------------
+        case DW_OP_call_frame_cfa:
+            if (frame)
+            {
+                // Note that we don't have to parse FDEs because this DWARF expression
+                // is commonly evaluated with a valid stack frame.
+                StackID id = frame->GetStackID();                
+                addr_t cfa = id.GetCallFrameAddress();
+                if (cfa != LLDB_INVALID_ADDRESS)
+                {
+                    stack.push_back(Scalar(cfa));
+                    stack.back().SetValueType (Value::eValueTypeHostAddress);
+                }
+                else
+                    if (error_ptr)
+                        error_ptr->SetErrorString ("Stack frame does not include a canonical frame address for DW_OP_call_frame_cfa opcode.");
+            }
+            else
+            {
+                if (error_ptr)
+                    error_ptr->SetErrorString ("Invalid stack frame in context for DW_OP_call_frame_cfa opcode.");
+                return false;
+            }
+            break;
         }
     }
 
diff --git a/lldb/source/Symbol/DWARFCallFrameInfo.cpp b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
index 003b945..e8f99a9 100644
--- a/lldb/source/Symbol/DWARFCallFrameInfo.cpp
+++ b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
@@ -155,7 +155,7 @@ DWARFCallFrameInfo::ParseCIE (const dw_offset_t cie_offset)
         //    cie.offset = cie_offset;
         //    cie.length = length;
         //    cie.cieID = cieID;
-        cie_sp->ptr_encoding = DW_EH_PE_absptr;
+        cie_sp->ptr_encoding = DW_EH_PE_absptr; // default
         cie_sp->version = m_cfi_data.GetU8(&offset);
 
         for (i=0; i<CFI_AUG_MAX_SIZE; ++i)
@@ -233,6 +233,7 @@ DWARFCallFrameInfo::ParseCIE (const dw_offset_t cie_offset)
                             // Data shall include a 1 byte argument that
                             // represents the pointer encoding for the address
                             // pointers used in the FDE.
+                            // Example: 0x1B == DW_EH_PE_pcrel | DW_EH_PE_sdata4 
                             cie_sp->ptr_encoding = m_cfi_data.GetU8(&offset);
                             break;
                     }
-- 
2.7.4