[lldb] [llvm] Stateful variable-location annotations in Disassembler::PrintInstructions() (follow-up to #147460) (PR #152887)

[Jonas Devlieghere via llvm-commits]

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@@ -376,6 +382,147 @@ void Disassembler::PrintInstructions(Debugger &debugger, const ArchSpec &arch,
     }
   }
 
+  // Add variable location annotations to the disassembly output.
+  //
+  // For each instruction, this block attempts to resolve in-scope variables
+  // and determine if the current PC falls within their
+  // DWARF location entry. If so, it prints a simplified annotation using the
+  // variable name and its resolved location (e.g., "var = reg; " ).
+  //
+  // Annotations are only included if the variable has a valid DWARF location
+  // entry, and the location string is non-empty after filtering. Decoding
+  // errors and DWARF opcodes are intentionally omitted to keep the output
+  // concise and user-friendly.
+  //
+  // The goal is to give users helpful live variable hints alongside the
+  // disassembled instruction stream, similar to how debug information
+  // enhances source-level debugging.
+
+  struct VarState {
+    std::string name;     ///< Display name.
+    std::string last_loc; ///< Last printed location (empty means <undef>).
+    bool seen_this_inst = false;
+  };
+
+  // Track live variables across instructions.
+  llvm::DenseMap<lldb::user_id_t, VarState> live_vars;
+
+  // Stateful annotator: updates live_vars and returns only what should be
+  // printed for THIS instruction.
+  auto annotate_static = [&](Instruction &inst, Target &target,
+                             ModuleSP module_sp) -> std::vector<std::string> {
+    std::vector<std::string> events;
+
+    // Reset per-instruction seen flags.
+    for (auto &kv : live_vars)
+      kv.second.seen_this_inst = false;
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JDevlieghere wrote:

Do you need to remember the key still? Can you just clear the map?

https://github.com/llvm/llvm-project/pull/152887