diff --git a/src/compiler/build_tables/build_lex_table.cc b/src/compiler/build_tables/build_lex_table.cc
index 94100349..d55e1c94 100644
--- a/src/compiler/build_tables/build_lex_table.cc
+++ b/src/compiler/build_tables/build_lex_table.cc
@@ -44,7 +44,7 @@ class LexTableBuilder {
   const LexicalGrammar lex_grammar;
   vector<rule_ptr> separator_rules;
   LexConflictManager conflict_manager;
-  unordered_map<const LexItemSet, LexStateId, LexItemSet::Hash> lex_state_ids;
+  unordered_map<LexItemSet, LexStateId> lex_state_ids;
 
  public:
   LexTableBuilder(ParseTable *parse_table, const LexicalGrammar &lex_grammar)
diff --git a/src/compiler/build_tables/build_parse_table.cc b/src/compiler/build_tables/build_parse_table.cc
index a8d38973..17fbdea6 100644
--- a/src/compiler/build_tables/build_parse_table.cc
+++ b/src/compiler/build_tables/build_parse_table.cc
@@ -36,7 +36,7 @@ class ParseTableBuilder {
   const LexicalGrammar lexical_grammar;
   ParseConflictManager conflict_manager;
   unordered_map<Symbol, ParseItemSet> recovery_states;
-  unordered_map<ParseItemSet, ParseStateId, ParseItemSet::Hash> parse_state_ids;
+  unordered_map<ParseItemSet, ParseStateId> parse_state_ids;
   vector<pair<ParseItemSet, ParseStateId>> item_sets_to_process;
   ParseTable parse_table;
   set<string> conflicts;
@@ -146,8 +146,8 @@ class ParseTableBuilder {
     auto pair = parse_state_ids.find(item_set);
     if (pair == parse_state_ids.end()) {
       ParseStateId state_id = parse_table.add_state();
-
       parse_state_ids[item_set] = state_id;
+      parse_table.states[state_id].shift_actions_signature = item_set.unfinished_item_signature();
       item_sets_to_process.push_back({ std::move(item_set), state_id });
       return state_id;
     } else {
@@ -172,7 +172,8 @@ class ParseTableBuilder {
           new_action->state_index = add_parse_state(next_item_set);
         }
       } else {
-        parse_table.set_nonterminal_action(state_id, symbol.index, add_parse_state(next_item_set));
+        ParseStateId next_state = add_parse_state(next_item_set);
+        parse_table.set_nonterminal_action(state_id, symbol.index, next_state);
       }
     }
   }
@@ -250,7 +251,76 @@ class ParseTableBuilder {
   }
 
   void remove_duplicate_parse_states() {
-    remove_duplicate_states<ParseTable>(&parse_table);
+    map<size_t, set<ParseStateId>> state_indices_by_signature;
+
+    for (ParseStateId i = 0, n = parse_table.states.size(); i < n; i++) {
+      ParseState &state = parse_table.states[i];
+      state_indices_by_signature[state.shift_actions_signature].insert(i);
+    }
+
+    set<ParseStateId> deleted_states;
+
+    while (true) {
+      std::map<ParseStateId, ParseStateId> state_replacements;
+
+      for (auto &pair : state_indices_by_signature) {
+        auto &state_group = pair.second;
+
+        for (ParseStateId i : state_group) {
+          for (ParseStateId j : state_group) {
+            if (j == i) break;
+            if (!state_replacements.count(j) && parse_table.merge_state(j, i)) {
+              state_replacements.insert({ i, j });
+              deleted_states.insert(i);
+              break;
+            }
+          }
+        }
+      }
+
+      if (state_replacements.empty()) break;
+
+      for (ParseStateId i = 0, n = parse_table.states.size(); i < n; i++) {
+        ParseState &state = parse_table.states[i];
+
+        if (state_replacements.count(i)) {
+          state_indices_by_signature[state.shift_actions_signature].erase(i);
+        } else {
+          state.each_referenced_state([&state_replacements](int64_t *state_index) {
+            auto replacement = state_replacements.find(*state_index);
+            if (replacement != state_replacements.end()) {
+              *state_index = replacement->second;
+            }
+          });
+        }
+      }
+    }
+
+    vector<ParseStateId> new_state_ids(parse_table.states.size());
+    size_t deleted_state_count = 0;
+    auto deleted_state_iter = deleted_states.begin();
+    for (size_t i = 0; i < new_state_ids.size(); i++) {
+      while (deleted_state_iter != deleted_states.end() && *deleted_state_iter < i) {
+        deleted_state_count++;
+        deleted_state_iter++;
+      }
+      new_state_ids[i] = i - deleted_state_count;
+    }
+
+    ParseStateId original_state_index = 0;
+    auto iter = parse_table.states.begin();
+    while (iter != parse_table.states.end()) {
+      if (deleted_states.count(original_state_index)) {
+        iter = parse_table.states.erase(iter);
+      } else {
+        ParseState &state = *iter;
+        state.each_referenced_state([&new_state_ids](int64_t *state_index) {
+          *state_index = new_state_ids[*state_index];
+        });
+        ++iter;
+      }
+      original_state_index++;
+    }
   }
 
   ParseAction *add_terminal_action(ParseStateId state_id, Symbol::Index lookahead,
diff --git a/src/compiler/build_tables/lex_item.cc b/src/compiler/build_tables/lex_item.cc
index 72c3b44d..5272f3bd 100644
--- a/src/compiler/build_tables/lex_item.cc
+++ b/src/compiler/build_tables/lex_item.cc
@@ -8,11 +8,11 @@
 #include "compiler/rules/symbol.h"
 #include "compiler/rules/repeat.h"
 #include "compiler/rules/visitor.h"
+#include "compiler/util/hash_combine.h"
 
 namespace tree_sitter {
 namespace build_tables {
 
-using std::hash;
 using std::map;
 using std::string;
 using std::unordered_set;
@@ -69,20 +69,9 @@ LexItem::CompletionStatus LexItem::completion_status() const {
   return GetCompletionStatus().apply(rule);
 }
 
-size_t LexItem::Hash::operator()(const LexItem &item) const {
-  return hash<Symbol>()(item.lhs) ^ hash<rule_ptr>()(item.rule);
-}
-
-size_t LexItemSet::Hash::operator()(const LexItemSet &item_set) const {
-  size_t result = hash<size_t>()(item_set.entries.size());
-  for (const auto &item : item_set.entries)
-    result ^= LexItem::Hash()(item);
-  return result;
-}
-
 LexItemSet::LexItemSet() {}
 
-LexItemSet::LexItemSet(const unordered_set<LexItem, LexItem::Hash> &entries)
+LexItemSet::LexItemSet(const unordered_set<LexItem> &entries)
     : entries(entries) {}
 
 bool LexItemSet::operator==(const LexItemSet &other) const {
@@ -103,3 +92,27 @@ bool LexItemSet::Transition::operator==(const LexItemSet::Transition &other) con
 
 }  // namespace build_tables
 }  // namespace tree_sitter
+
+namespace std {
+
+using tree_sitter::util::hash_combine;
+using tree_sitter::util::symmetric_hash_combine;
+using tree_sitter::build_tables::LexItem;
+using tree_sitter::build_tables::LexItemSet;
+
+size_t hash<LexItem>::operator()(const LexItem &item) const {
+  size_t result = 0;
+  hash_combine(&result, item.lhs.index);
+  hash_combine(&result, item.rule);
+  return result;
+}
+
+size_t hash<LexItemSet>::operator()(const LexItemSet &item_set) const {
+  size_t result = 0;
+  hash_combine(&result, item_set.entries.size());
+  for (const auto &item : item_set.entries)
+    symmetric_hash_combine(&result, item);
+  return result;
+}
+
+}  // namespace std
diff --git a/src/compiler/build_tables/lex_item.h b/src/compiler/build_tables/lex_item.h
index 80cd1e6b..4c45f80d 100644
--- a/src/compiler/build_tables/lex_item.h
+++ b/src/compiler/build_tables/lex_item.h
@@ -22,10 +22,6 @@ class LexItem {
     bool is_string;
   };
 
-  struct Hash {
-    size_t operator()(const LexItem &) const;
-  };
-
   bool operator==(const LexItem &other) const;
   CompletionStatus completion_status() const;
 
@@ -33,23 +29,34 @@ class LexItem {
   rule_ptr rule;
 };
 
+}  // namespace build_tables
+}  // namespace tree_sitter
+
+namespace std {
+
+template <>
+struct hash<tree_sitter::build_tables::LexItem> {
+  size_t operator()(const tree_sitter::build_tables::LexItem &) const;
+};
+
+}  // namespace std
+
+namespace tree_sitter {
+namespace build_tables {
+
 class LexItemSet {
  public:
   LexItemSet();
-  explicit LexItemSet(const std::unordered_set<LexItem, LexItem::Hash> &);
+  explicit LexItemSet(const std::unordered_set<LexItem> &);
 
   bool operator==(const LexItemSet &) const;
 
-  struct Hash {
-    size_t operator()(const LexItemSet &) const;
-  };
-
   struct Transition;
   typedef std::map<rules::CharacterSet, Transition> TransitionMap;
 
   TransitionMap transitions() const;
 
-  std::unordered_set<LexItem, LexItem::Hash> entries;
+  std::unordered_set<LexItem> entries;
 };
 
 struct LexItemSet::Transition {
@@ -63,4 +70,13 @@ struct LexItemSet::Transition {
 }  // namespace build_tables
 }  // namespace tree_sitter
 
+namespace std {
+
+template <>
+struct hash<tree_sitter::build_tables::LexItemSet> {
+  size_t operator()(const tree_sitter::build_tables::LexItemSet &) const;
+};
+
+}  // namespace std
+
 #endif  // COMPILER_BUILD_TABLES_LEX_ITEM_H_
diff --git a/src/compiler/build_tables/parse_item.cc b/src/compiler/build_tables/parse_item.cc
index 5054e578..d691998f 100644
--- a/src/compiler/build_tables/parse_item.cc
+++ b/src/compiler/build_tables/parse_item.cc
@@ -2,6 +2,7 @@
 #include <string>
 #include "compiler/syntax_grammar.h"
 #include "compiler/rules/built_in_symbols.h"
+#include "compiler/util/hash_combine.h"
 
 namespace tree_sitter {
 namespace build_tables {
@@ -10,8 +11,10 @@ using std::map;
 using std::pair;
 using std::string;
 using std::to_string;
-using std::hash;
 using rules::Symbol;
+using util::hash_combine;
+
+ParseItem::ParseItem() : variable_index(-1), production(nullptr), step_index(0) {}
 
 ParseItem::ParseItem(const Symbol &lhs, const Production &production,
                      unsigned int step_index)
@@ -78,13 +81,6 @@ rules::Associativity ParseItem::associativity() const {
     return production->at(step_index).associativity;
 }
 
-size_t ParseItem::Hash::operator()(const ParseItem &item) const {
-  size_t result = hash<int>()(item.variable_index);
-  result ^= hash<unsigned int>()(item.step_index);
-  result ^= hash<const void *>()(static_cast<const void *>(item.production));
-  return result;
-}
-
 ParseItemSet::ParseItemSet() {}
 
 ParseItemSet::ParseItemSet(const map<ParseItem, LookaheadSet> &entries)
@@ -94,16 +90,19 @@ bool ParseItemSet::operator==(const ParseItemSet &other) const {
   return entries == other.entries;
 }
 
-size_t ParseItemSet::Hash::operator()(const ParseItemSet &item_set) const {
-  size_t result = hash<size_t>()(item_set.entries.size());
-  for (auto &pair : item_set.entries) {
+size_t ParseItemSet::unfinished_item_signature() const {
+  size_t result = 0;
+  ParseItem previous_item;
+  for (auto &pair : entries) {
     const ParseItem &item = pair.first;
-    result ^= ParseItem::Hash()(item);
-
-    const LookaheadSet &lookahead_set = pair.second;
-    result ^= hash<size_t>()(lookahead_set.entries->size());
-    for (Symbol::Index index : *pair.second.entries)
-      result ^= hash<Symbol::Index>()(index);
+    if (item.step_index < item.production->size()) {
+      if (item.variable_index != previous_item.variable_index &&
+          item.step_index != previous_item.step_index) {
+        hash_combine(&result, item.variable_index);
+        hash_combine(&result, item.step_index);
+        previous_item = item;
+      }
+    }
   }
   return result;
 }
@@ -135,3 +134,37 @@ void ParseItemSet::add(const ParseItemSet &other) {
 
 }  // namespace build_tables
 }  // namespace tree_sitter
+
+namespace std {
+
+using tree_sitter::build_tables::ParseItem;
+using tree_sitter::build_tables::ParseItemSet;
+using tree_sitter::util::hash_combine;
+
+template <>
+struct hash<ParseItem> {
+  size_t operator()(const ParseItem &item) const {
+    size_t result = 0;
+    hash_combine(&result, item.variable_index);
+    hash_combine(&result, item.step_index);
+    hash_combine(&result, item.production);
+    return result;
+  }
+};
+
+size_t hash<ParseItemSet>::operator()(const ParseItemSet &item_set) const {
+  size_t result = 0;
+  hash_combine(&result, item_set.entries.size());
+  for (auto &pair : item_set.entries) {
+    const ParseItem &item = pair.first;
+    const auto &lookahead_set = pair.second;
+
+    hash_combine(&result, item);
+    hash_combine(&result, lookahead_set.entries->size());
+    for (auto index : *pair.second.entries)
+      hash_combine(&result, index);
+  }
+  return result;
+}
+
+}  // namespace std
diff --git a/src/compiler/build_tables/parse_item.h b/src/compiler/build_tables/parse_item.h
index 404b67c3..b8a78480 100644
--- a/src/compiler/build_tables/parse_item.h
+++ b/src/compiler/build_tables/parse_item.h
@@ -14,6 +14,7 @@ namespace build_tables {
 
 class ParseItem {
  public:
+  ParseItem();
   ParseItem(const rules::Symbol &, const Production &, unsigned int);
 
   struct CompletionStatus {
@@ -22,10 +23,6 @@ class ParseItem {
     rules::Associativity associativity;
   };
 
-  struct Hash {
-    size_t operator()(const ParseItem &) const;
-  };
-
   bool operator==(const ParseItem &other) const;
   bool operator<(const ParseItem &other) const;
   rules::Symbol lhs() const;
@@ -47,13 +44,10 @@ class ParseItemSet {
   typedef std::map<rules::Symbol, std::pair<ParseItemSet, PrecedenceRange>>
     TransitionMap;
 
-  struct Hash {
-    size_t operator()(const ParseItemSet &) const;
-  };
-
   TransitionMap transitions() const;
   bool operator==(const ParseItemSet &) const;
   void add(const ParseItemSet &);
+  size_t unfinished_item_signature() const;
 
   std::map<ParseItem, LookaheadSet> entries;
 };
@@ -61,4 +55,15 @@ class ParseItemSet {
 }  // namespace build_tables
 }  // namespace tree_sitter
 
+namespace std {
+
+using tree_sitter::build_tables::ParseItemSet;
+
+template <>
+struct hash<tree_sitter::build_tables::ParseItemSet> {
+  size_t operator()(const ParseItemSet &item_set) const;
+};
+
+}  // namespace std
+
 #endif  // COMPILER_BUILD_TABLES_PARSE_ITEM_H_
diff --git a/src/compiler/parse_table.h b/src/compiler/parse_table.h
index 5f660ecd..81142f75 100644
--- a/src/compiler/parse_table.h
+++ b/src/compiler/parse_table.h
@@ -47,6 +47,7 @@ class ParseAction {
   rules::Symbol symbol;
   ParseStateId state_index;
   size_t consumed_symbol_count;
+
   PrecedenceRange precedence_range;
   rules::Associativity associativity;
   const Production *production;
@@ -78,6 +79,7 @@ class ParseState {
   std::map<rules::Symbol::Index, ParseTableEntry> terminal_entries;
   std::map<rules::Symbol::Index, ParseStateId> nonterminal_entries;
   LexStateId lex_state_id;
+  size_t shift_actions_signature;
 };
 
 struct ParseTableSymbolMetadata {
diff --git a/src/compiler/rules/character_set.cc b/src/compiler/rules/character_set.cc
index 9c273575..cff3ab58 100644
--- a/src/compiler/rules/character_set.cc
+++ b/src/compiler/rules/character_set.cc
@@ -3,14 +3,15 @@
 #include <utility>
 #include <vector>
 #include "compiler/rules/visitor.h"
+#include "compiler/util/hash_combine.h"
 
 namespace tree_sitter {
 namespace rules {
 
 using std::string;
-using std::hash;
 using std::set;
 using std::vector;
+using util::hash_combine;
 
 static void add_range(set<uint32_t> *characters, uint32_t min, uint32_t max) {
   for (uint32_t c = min; c <= max; c++)
@@ -83,14 +84,14 @@ bool CharacterSet::operator<(const CharacterSet &other) const {
 }
 
 size_t CharacterSet::hash_code() const {
-  size_t result = hash<bool>()(includes_all);
-  result ^= hash<size_t>()(included_chars.size());
-  for (auto &c : included_chars)
-    result ^= hash<uint32_t>()(c);
-  result <<= 1;
-  result ^= hash<size_t>()(excluded_chars.size());
-  for (auto &c : excluded_chars)
-    result ^= hash<uint32_t>()(c);
+  size_t result = 0;
+  hash_combine(&result, includes_all);
+  hash_combine(&result, included_chars.size());
+  for (uint32_t c : included_chars)
+    hash_combine(&result, c);
+  hash_combine(&result, excluded_chars.size());
+  for (uint32_t c : excluded_chars)
+    hash_combine(&result, c);
   return result;
 }
 
diff --git a/src/compiler/rules/choice.cc b/src/compiler/rules/choice.cc
index 975adbef..c793aed1 100644
--- a/src/compiler/rules/choice.cc
+++ b/src/compiler/rules/choice.cc
@@ -2,6 +2,7 @@
 #include <string>
 #include <set>
 #include "compiler/rules/visitor.h"
+#include "compiler/util/hash_combine.h"
 
 namespace tree_sitter {
 namespace rules {
@@ -10,6 +11,7 @@ using std::string;
 using std::make_shared;
 using std::vector;
 using std::set;
+using util::symmetric_hash_combine;
 
 Choice::Choice(const vector<rule_ptr> &elements) : elements(elements) {}
 
@@ -50,9 +52,10 @@ bool Choice::operator==(const Rule &rule) const {
 }
 
 size_t Choice::hash_code() const {
-  size_t result = std::hash<size_t>()(elements.size());
+  size_t result = 0;
+  symmetric_hash_combine(&result, elements.size());
   for (const auto &element : elements)
-    result ^= element->hash_code();
+    symmetric_hash_combine(&result, element);
   return result;
 }
 
diff --git a/src/compiler/rules/metadata.cc b/src/compiler/rules/metadata.cc
index a2512861..97fd0fed 100644
--- a/src/compiler/rules/metadata.cc
+++ b/src/compiler/rules/metadata.cc
@@ -3,14 +3,15 @@
 #include <map>
 #include "compiler/rules/visitor.h"
 #include "compiler/rules/blank.h"
+#include "compiler/util/hash_combine.h"
 
 namespace tree_sitter {
 namespace rules {
 
-using std::hash;
 using std::make_shared;
 using std::map;
 using std::pair;
+using util::hash_combine;
 
 Metadata::Metadata(rule_ptr rule, map<MetadataKey, int> values)
     : rule(rule), value(values) {}
@@ -25,10 +26,11 @@ bool Metadata::operator==(const Rule &rule) const {
 }
 
 size_t Metadata::hash_code() const {
-  size_t result = hash<size_t>()(value.size());
+  size_t result = 0;
+  hash_combine(&result, value.size());
   for (auto &pair : value) {
-    result ^= hash<int>()(pair.first);
-    result ^= hash<int>()(pair.second);
+    hash_combine<int>(&result, pair.first);
+    hash_combine(&result, pair.second);
   }
   return result;
 }
diff --git a/src/compiler/rules/symbol.cc b/src/compiler/rules/symbol.cc
index 96c4bd60..f85b09c7 100644
--- a/src/compiler/rules/symbol.cc
+++ b/src/compiler/rules/symbol.cc
@@ -2,13 +2,14 @@
 #include <string>
 #include <map>
 #include "compiler/rules/visitor.h"
+#include "compiler/util/hash_combine.h"
 
 namespace tree_sitter {
 namespace rules {
 
 using std::string;
 using std::to_string;
-using std::hash;
+using util::hash_combine;
 
 Symbol::Symbol(Symbol::Index index) : index(index), is_token(false) {}
 
@@ -24,7 +25,10 @@ bool Symbol::operator==(const Rule &rule) const {
 }
 
 size_t Symbol::hash_code() const {
-  return hash<Symbol::Index>()(index) ^ hash<bool>()(is_token);
+  size_t result = 0;
+  hash_combine(&result, index);
+  hash_combine(&result, is_token);
+  return result;
 }
 
 rule_ptr Symbol::copy() const {
diff --git a/src/compiler/util/hash_combine.h b/src/compiler/util/hash_combine.h
new file mode 100644
index 00000000..9cc3ad17
--- /dev/null
+++ b/src/compiler/util/hash_combine.h
@@ -0,0 +1,24 @@
+#ifndef COMPILER_UTIL_HASH_COMBINE_H_
+#define COMPILER_UTIL_HASH_COMBINE_H_
+
+#include <functional>
+
+namespace tree_sitter {
+namespace util {
+
+template <class T>
+inline void hash_combine(std::size_t *seed, const T &new_value) {
+  std::hash<T> hasher;
+  *seed ^= hasher(new_value) + 0x9e3779b9 + (*seed << 6) + (*seed >> 2);
+}
+
+template <class T>
+inline void symmetric_hash_combine(std::size_t *seed, const T &new_value) {
+  std::hash<T> hasher;
+  *seed ^= hasher(new_value);
+}
+
+}  // namespace util
+}  // namespace tree_sitter
+
+#endif  // COMPILER_UTIL_HASH_COMBINE_H_