update readme and fix unused function issue (#821)

decompiler/Disasm/InstructionMatching.cpp

@@ -288,7 +288,8 @@ bool is_gpr_2_imm_int(const Instruction& instr,
                       MatchParam<Register> src,
                       MatchParam<int32_t> imm) {
   return kind == instr.kind && dst == instr.get_dst(0).get_reg() &&
-         src == instr.get_src(0).get_reg() && imm == instr.get_src(1).get_imm();
+         src == instr.get_src(0).get_reg() && instr.get_src(1).is_imm() &&
+         imm == instr.get_src(1).get_imm();
 }
 
 /*!

decompiler/IR2/LabelDB.cpp

@@ -102,6 +102,15 @@ int LabelDB::get_index_by_offset(int seg, int offset) const {
   return m_labels_by_offset_into_seg.at(seg).at(offset);
 }
 
+std::optional<int> LabelDB::try_get_index_by_offset(int seg, int offset) const {
+  auto it = m_labels_by_offset_into_seg.at(seg).find(offset);
+  if (it == m_labels_by_offset_into_seg.at(seg).end()) {
+    return {};
+  } else {
+    return it->second;
+  }
+}
+
 int LabelDB::get_index_by_name(const std::string& name) const {
   return m_labels_by_name.at(name);
 }

decompiler/IR2/LabelDB.h

@@ -31,6 +31,7 @@ class LabelDB {
   const LabelInfo& lookup(int idx) const;
   const LabelInfo& lookup(const std::string& name) const;
   int get_index_by_offset(int seg, int offset) const;
+  std::optional<int> try_get_index_by_offset(int seg, int offset) const;
   int get_index_by_name(const std::string& name) const;
 
   LabelInfo set_and_get_previous(int idx,

decompiler/ObjectFile/ObjectFileDB_IR2.cpp

@@ -639,7 +639,14 @@ void ObjectFileDB::ir2_insert_lets(int seg) {
   for_each_function_in_seg(seg, [&](Function& func, ObjectFileData&) {
     if (func.ir2.expressions_succeeded) {
       attempted++;
-      combined_stats += insert_lets(func, func.ir2.env, *func.ir2.form_pool, func.ir2.top_form);
+      try {
+        combined_stats += insert_lets(func, func.ir2.env, *func.ir2.form_pool, func.ir2.top_form);
+      } catch (const std::exception& e) {
+        func.warnings.general_warning(
+            fmt::format("Error while inserting lets: {}\n Make sure that the return type is not "
+                        "none if something is actually returned.",
+                        e.what()));
+      }
     }
   });
 

decompiler/analysis/label_types.cpp

@@ -53,12 +53,17 @@ void find_functions(LabelDB* db, LinkedObjectFile* file) {
         // first, the label for the start of the function
         // + 4 bytes for the type tag.
         int offset_of_function = func.start_word * 4 + 4;
-        int idx_of_label = db->get_index_by_offset(seg, offset_of_function);
-        auto old = db->set_and_get_previous(idx_of_label, func.type, false, {});
-        if (old.known) {
-          throw std::runtime_error(fmt::format(
-              "There is a config entry for label {}, but it's a function. Remove the config.",
-              old.name));
+        auto idx_of_label = db->try_get_index_by_offset(seg, offset_of_function);
+        if (!idx_of_label) {
+          func.warnings.general_warning("Could not find any references to this function: {}",
+                                        func.guessed_name.to_string());
+        } else {
+          auto old = db->set_and_get_previous(*idx_of_label, func.type, false, {});
+          if (old.known) {
+            throw std::runtime_error(fmt::format(
+                "There is a config entry for label {}, but it's a function. Remove the config.",
+                old.name));
+          }
         }
       }
 
@@ -73,7 +78,9 @@ void find_boxed(LabelDB* db, LinkedObjectFile* file) {
     if ((lab.offset & 7) == BASIC_OFFSET) {
       // it's a basic! probably.
       const auto& word = file->words_by_seg.at(lab.target_segment).at((lab.offset - 4) / 4);
-      if (word.kind == LinkedWord::TYPE_PTR) {
+      // the snowball-bank is a weird basic with no fields other than the built-in type.
+      // so it can actually share a label with something else.
+      if (word.kind == LinkedWord::TYPE_PTR && word.symbol_name != "snowball-bank") {
         TypeSpec basic_type(word.symbol_name);
         const auto& existing = db->lookup(lab.name);
         if (existing.known) {

decompiler/util/data_decompile.cpp

@@ -351,7 +351,12 @@ goos::Object decomp_ref_to_inline_array_guess_size(
   const auto& start_label = labels.at(pointer_to_data.label_id);
   int end_label_idx =
       index_of_closest_following_label_in_segment(start_label.offset, my_seg, labels);
-  assert(end_label_idx >= 0);
+
+  if (end_label_idx < 0) {
+    throw std::runtime_error(
+        "Failed to find label: likely just an unimplemented case for when the data is the last "
+        "thing in the file.");
+  }
   const auto& end_label = labels.at(end_label_idx);
   // fmt::print("Data is from {} to {}\n", start_label.name, end_label.name);