[Lldb-commits] [lldb] [lldb] Add isConstant mode for FA locations (PR #110726)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-lldb

Author: Felipe de Azevedo Piovezan (felipepiovezan)

<details>
<summary>Changes</summary>

This is similar to 9fe455fd0c7d, but for FA locations instead of register locations.
This is useful for unwind plans that cannot create abstract unwind rules, but instead must inspect the state of the program to determine the current CFA.

---
Full diff: https://github.com/llvm/llvm-project/pull/110726.diff


3 Files Affected:

- (modified) lldb/include/lldb/Symbol/UnwindPlan.h (+12) 
- (modified) lldb/source/Symbol/UnwindPlan.cpp (+4) 
- (modified) lldb/source/Target/RegisterContextUnwind.cpp (+6) 


``````````diff
diff --git a/lldb/include/lldb/Symbol/UnwindPlan.h b/lldb/include/lldb/Symbol/UnwindPlan.h
index e1567c7357d0b5..48c9bef76857c0 100644
--- a/lldb/include/lldb/Symbol/UnwindPlan.h
+++ b/lldb/include/lldb/Symbol/UnwindPlan.h
@@ -215,6 +215,7 @@ class UnwindPlan {
         isRegisterDereferenced, // FA = [reg]
         isDWARFExpression,      // FA = eval(dwarf_expr)
         isRaSearch,             // FA = SP + offset + ???
+        isConstant,             // FA = constant
       };
 
       FAValue() : m_value() {}
@@ -259,6 +260,15 @@ class UnwindPlan {
         m_value.expr.length = len;
       }
 
+      bool IsConstant() const { return m_type == isConstant; }
+
+      void SetIsConstant(uint64_t constant) {
+        m_type = isConstant;
+        m_value.constant = constant;
+      }
+
+      uint64_t GetConstant() const { return m_value.constant; }
+
       uint32_t GetRegisterNumber() const {
         if (m_type == isRegisterDereferenced || m_type == isRegisterPlusOffset)
           return m_value.reg.reg_num;
@@ -329,6 +339,8 @@ class UnwindPlan {
         } expr;
         // For m_type == isRaSearch
         int32_t ra_search_offset;
+        // For m_type = isConstant
+        uint64_t constant;
       } m_value;
     }; // class FAValue
 
diff --git a/lldb/source/Symbol/UnwindPlan.cpp b/lldb/source/Symbol/UnwindPlan.cpp
index a06e7cfd7f5446..25e3676761436e 100644
--- a/lldb/source/Symbol/UnwindPlan.cpp
+++ b/lldb/source/Symbol/UnwindPlan.cpp
@@ -187,6 +187,8 @@ operator==(const UnwindPlan::Row::FAValue &rhs) const {
         return !memcmp(m_value.expr.opcodes, rhs.m_value.expr.opcodes,
                        m_value.expr.length);
       break;
+    case isConstant:
+      return m_value.constant == rhs.m_value.constant;
     }
   }
   return false;
@@ -214,6 +216,8 @@ void UnwindPlan::Row::FAValue::Dump(Stream &s, const UnwindPlan *unwind_plan,
   case isRaSearch:
     s.Printf("RaSearch at SP%+d", m_value.ra_search_offset);
     break;
+  case isConstant:
+    s.Printf("0x%" PRIx64, m_value.constant);
   }
 }
 
diff --git a/lldb/source/Target/RegisterContextUnwind.cpp b/lldb/source/Target/RegisterContextUnwind.cpp
index b683ea7237de04..8f4def9840712f 100644
--- a/lldb/source/Target/RegisterContextUnwind.cpp
+++ b/lldb/source/Target/RegisterContextUnwind.cpp
@@ -2088,6 +2088,12 @@ bool RegisterContextUnwind::ReadFrameAddress(
     UnwindLogMsg("No suitable CFA found");
     break;
   }
+  case UnwindPlan::Row::FAValue::isConstant: {
+    address = fa.GetConstant();
+    address = abi_sp->FixCodeAddress(address);
+    UnwindLogMsg("CFA value set by constant is 0x%" PRIx64, address);
+    return true;
+  }
   default:
     return false;
   }

``````````

</details>


https://github.com/llvm/llvm-project/pull/110726