[lldb][gardening] Refactor "MakeGenericSignaturesAndCalls"

Author: augusto2112

lldb/source/Plugins/ExpressionParser/Swift/SwiftExpressionSourceCode.cpp

@@ -114,6 +114,47 @@ struct CallsAndArgs {
   std::string lldb_call;
 };
 
+static llvm::SmallVector<const SwiftASTManipulator::VariableInfo *>
+CollectMetadataVariables(
+    llvm::ArrayRef<SwiftASTManipulator::VariableInfo> local_variables) {
+  llvm::SmallVector<const SwiftASTManipulator::VariableInfo *>
+      metadata_variables;
+  for (auto &var : local_variables)
+    if (var.IsOutermostMetadataPointer())
+      metadata_variables.push_back(&var);
+  return metadata_variables;
+}
+
+struct PackAndIndex {
+  bool is_pack = false;
+  unsigned depth, index;
+
+  PackAndIndex(bool is_pack, unsigned depth, unsigned index)
+      : is_pack(is_pack), depth(depth), index(index) {}
+};
+
+static llvm::Expected<llvm::SmallVector<PackAndIndex>> CollectPacksAndIndexes(
+    llvm::ArrayRef<const SwiftASTManipulator::VariableInfo *>
+        metadata_variables,
+    const std::optional<SwiftLanguageRuntime::GenericSignature> &generic_sig) {
+  llvm::SmallVector<PackAndIndex> pack_and_indexes;
+
+  if (generic_sig) {
+    for (auto &generic_param : generic_sig->generic_params)
+      pack_and_indexes.emplace_back(generic_param.is_pack, generic_param.depth, generic_param.index);
+  } else {
+    for (auto *metadata_variable : metadata_variables) {
+      auto maybe_depth_and_index =
+          ParseSwiftGenericParameter(metadata_variable->GetName().str());
+      if (!maybe_depth_and_index)
+        return llvm::createStringError(llvm::errc::not_supported,
+                                       "unexpected metadata variable");
+      pack_and_indexes.emplace_back(false, maybe_depth_and_index->first,
+                                    maybe_depth_and_index->second);
+    }
+  }
+  return pack_and_indexes;
+}
 /// Constructs the signatures for the expression evaluation functions based on
 /// the metadata variables in scope and any variadic functiontion parameters.
 /// For every outermost metadata pointer in scope ($τ_0_0, $τ_0_1, etc), we want
@@ -149,50 +190,36 @@ static llvm::Expected<CallsAndArgs> MakeGenericSignaturesAndCalls(
     llvm::ArrayRef<SwiftASTManipulator::VariableInfo> local_variables,
     const std::optional<SwiftLanguageRuntime::GenericSignature> &generic_sig,
     bool needs_object_ptr) {
-  llvm::SmallVector<const SwiftASTManipulator::VariableInfo *>
-      metadata_variables;
-  for (auto &var : local_variables)
-    if (var.IsOutermostMetadataPointer())
-      metadata_variables.push_back(&var);
-
+  auto metadata_variables = CollectMetadataVariables(local_variables);
   // The number of metadata variables could be > if the function is in
   // a generic context.
   if (generic_sig &&
       (metadata_variables.size() < generic_sig->dependent_generic_param_count))
     return llvm::createStringError(llvm::errc::not_supported,
                                    "Inconsistent generic signature");
 
+  auto maybe_pack_and_indexes = CollectPacksAndIndexes(metadata_variables, generic_sig);
+  if (!maybe_pack_and_indexes)
+    return maybe_pack_and_indexes.takeError();
+  auto pack_and_indexes = *maybe_pack_and_indexes;
+
   llvm::SmallDenseMap<std::pair<unsigned, unsigned>, llvm::SmallString<4>> subs;
   std::string generic_params;
   std::string generic_params_no_packs;
   llvm::raw_string_ostream s_generic_params(generic_params);
   llvm::raw_string_ostream s_generic_params_no_packs(generic_params_no_packs);
-  for (size_t i = 0; i < metadata_variables.size(); ++i) {
+
+  for (size_t i = 0; i < pack_and_indexes.size(); ++i) {
+    auto &[is_pack, depth, index] = pack_and_indexes[i];
     llvm::SmallString<4> archetype_name;
     llvm::raw_svector_ostream s_archetype_name(archetype_name);
-    bool is_pack = false;
-    unsigned depth, index;
-    if (generic_sig) {
-      auto &gp = generic_sig->generic_params[i];
-      is_pack = gp.is_pack;
-      depth = gp.depth;
-      index = gp.index;
-    } else {
-      auto di =
-          ParseSwiftGenericParameter(metadata_variables[i]->GetName().str());
-      if (!di)
-        return llvm::createStringError(llvm::errc::not_supported,
-                                       "unexpected metadata variable");
-      depth = di->first;
-      index = di->second;
-    }
     if (is_pack)
       s_archetype_name << "each ";
     s_archetype_name << "T" << i;
     if (!is_pack)
       s_generic_params_no_packs << archetype_name << ",";
-    subs.insert({{depth, index}, archetype_name});
     s_generic_params << archetype_name << ",";
+    subs.insert({{depth, index}, archetype_name});
   }
 
   if (!generic_params.empty())