Revert "[ELF] Compile an Aho-Corasick tree into a DFA"

This reverts commit 31ca2cc2ae
because looks like it's slower than before.

elf/mold.h

@@ -1131,22 +1131,14 @@ private:
     u32 value = -1;
     TrieNode *suffix_link = nullptr;
     std::unique_ptr<TrieNode> children[256];
-    u32 dfa_idx = -1;
-  };
-
-  struct DfaState {
-    u32 value = -1;
-    u32 children[256] = {};
   };
 
   void compile();
   void fix_suffix_links(TrieNode &node);
   void fix_value();
-  void encode(TrieNode &node);
 
   std::vector<std::string> strings;
   std::unique_ptr<TrieNode> root;
-  std::vector<DfaState> dfa_states;
   std::vector<std::pair<GlobPattern, u32>> globs;
   std::vector<u16> versions;
   std::once_flag once_flag;

elf/version-matcher.cc

@@ -29,11 +29,21 @@ std::optional<u16> VersionMatcher::find(std::string_view str) {
     std::call_once(once_flag, [&]() { compile(); });
 
     // Match against simple glob patterns
-    DfaState *dfa = &dfa_states[0];
+    TrieNode *node = root.get();
 
     auto walk = [&](u8 c) {
-      dfa = &dfa_states[dfa->children[c]];
-      idx = std::min(idx, dfa->value);
+      for (;;) {
+        if (node->children[c]) {
+          node = node->children[c].get();
+          idx = std::min(idx, node->value);
+          return;
+        }
+
+        if (!node->suffix_link)
+          return;
+        node = node->suffix_link;
+        idx = std::min(idx, node->value);
+      }
     };
 
     walk('\0');
@@ -107,7 +117,6 @@ bool VersionMatcher::add(std::string_view pat, u16 ver) {
 void VersionMatcher::compile() {
   fix_suffix_links(*root);
   fix_value();
-  encode(*root);
   compiled = true;
 }
 
@@ -154,22 +163,4 @@ void VersionMatcher::fix_value() {
   } while (!queue.empty());
 }
 
-void VersionMatcher::encode(TrieNode &node) {
-  if (node.dfa_idx != -1)
-    return;
-
-  node.dfa_idx = dfa_states.size();
-  dfa_states.push_back({node.value});
-
-  for (i64 i = 0; i < 256; i++) {
-    for (TrieNode *t = &node; t; t = t->suffix_link) {
-      if (std::unique_ptr<TrieNode> &next = t->children[i]) {
-        encode(*next);
-        dfa_states[node.dfa_idx].children[i] = next->dfa_idx;
-        break;
-      }
-    }
-  }
-}
-
 } // namespace mold::elf