diff --git a/CMakeLists.txt b/CMakeLists.txt
index aafae5d9..af9bcc1a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -201,7 +201,6 @@ target_sources(ccls PRIVATE
   src/filesystem.cc
   src/fuzzy_match.cc
   src/main.cc
-  src/include_complete.cc
   src/indexer.cc
   src/log.cc
   src/lsp.cc
diff --git a/src/clang_tu.cc b/src/clang_tu.cc
index 664f6fbb..32be1733 100644
--- a/src/clang_tu.cc
+++ b/src/clang_tu.cc
@@ -163,12 +163,7 @@ buildCompilerInvocation(const std::string &main, std::vector<const char *> args,
     return nullptr;
   const llvm::opt::ArgStringList &cc_args = cmd.getArguments();
   auto ci = std::make_unique<CompilerInvocation>();
-#if LLVM_VERSION_MAJOR >= 10 // rC370122
   if (!CompilerInvocation::CreateFromArgs(*ci, cc_args, *diags))
-#else
-  if (!CompilerInvocation::CreateFromArgs(
-          *ci, cc_args.data(), cc_args.data() + cc_args.size(), *diags))
-#endif
     return nullptr;
 
   ci->getDiagnosticOpts().IgnoreWarnings = true;
@@ -189,9 +184,7 @@ buildCompilerInvocation(const std::string &main, std::vector<const char *> args,
   auto &isec = ci->getFrontendOpts().Inputs;
   if (isec.size())
     isec[0] = FrontendInputFile(main, isec[0].getKind(), isec[0].isSystem());
-#if LLVM_VERSION_MAJOR >= 10 // llvmorg-11-init-2414-g75f09b54429
   ci->getPreprocessorOpts().DisablePragmaDebugCrash = true;
-#endif
   // clangSerialization has an unstable format. Disable PCH reading/writing
   // to work around PCH mismatch problems.
   ci->getPreprocessorOpts().ImplicitPCHInclude.clear();
diff --git a/src/clang_tu.hh b/src/clang_tu.hh
index b3288eb7..fd98ced1 100644
--- a/src/clang_tu.hh
+++ b/src/clang_tu.hh
@@ -10,13 +10,6 @@
 #include <clang/Basic/SourceManager.h>
 #include <clang/Frontend/CompilerInstance.h>
 
-#if LLVM_VERSION_MAJOR < 8
-// D52783 Lift VFS from clang to llvm
-namespace llvm {
-namespace vfs = clang::vfs;
-}
-#endif
-
 #if LLVM_VERSION_MAJOR < 14 // llvmorg-14-init-3863-g601102d282d5
 #define isAsciiIdentifierContinue isIdentifierBody
 #endif
diff --git a/src/include_complete.cc b/src/include_complete.cc
deleted file mode 100644
index 5fab581b..00000000
--- a/src/include_complete.cc
+++ /dev/null
@@ -1,185 +0,0 @@
-// Copyright 2017-2018 ccls Authors
-// SPDX-License-Identifier: Apache-2.0
-
-#include "include_complete.hh"
-
-#include "filesystem.hh"
-#include "platform.hh"
-#include "project.hh"
-
-#include <llvm/ADT/Twine.h>
-#include <llvm/Support/Threading.h>
-#include <llvm/Support/Timer.h>
-
-#include <unordered_set>
-using namespace llvm;
-
-#include <thread>
-
-namespace ccls {
-namespace {
-
-struct CompletionCandidate {
-  std::string absolute_path;
-  CompletionItem completion_item;
-};
-
-std::string elideLongPath(const std::string &path) {
-  if (g_config->completion.include.maxPathSize <= 0 ||
-      (int)path.size() <= g_config->completion.include.maxPathSize)
-    return path;
-
-  size_t start = path.size() - g_config->completion.include.maxPathSize;
-  return ".." + path.substr(start + 2);
-}
-
-size_t trimCommonPathPrefix(const std::string &result,
-                            const std::string &trimmer) {
-#ifdef _WIN32
-  std::string s = result, t = trimmer;
-  std::transform(s.begin(), s.end(), s.begin(), ::tolower);
-  std::transform(t.begin(), t.end(), t.begin(), ::tolower);
-  if (s.compare(0, t.size(), t) == 0)
-    return t.size();
-#else
-  if (result.compare(0, trimmer.size(), trimmer) == 0)
-    return trimmer.size();
-#endif
-  return 0;
-}
-
-int trimPath(Project *project, std::string &path) {
-  size_t pos = 0;
-  int kind = 0;
-  for (auto &[root, folder] : project->root2folder)
-    for (auto &[search, search_dir_kind] : folder.search_dir2kind)
-      if (int t = trimCommonPathPrefix(path, search); t > pos)
-        pos = t, kind = search_dir_kind;
-  path = path.substr(pos);
-  return kind;
-}
-
-CompletionItem buildCompletionItem(const std::string &path, int kind) {
-  CompletionItem item;
-  item.label = elideLongPath(path);
-  item.detail = path; // the include path, used in de-duplicating
-  item.textEdit.newText = path;
-  item.insertTextFormat = InsertTextFormat::PlainText;
-  item.kind = CompletionItemKind::File;
-  item.quote_kind_ = kind;
-  item.priority_ = 0;
-  return item;
-}
-} // namespace
-
-IncludeComplete::IncludeComplete(Project *project)
-    : is_scanning(false), project_(project) {}
-
-IncludeComplete::~IncludeComplete() {
-  // Spin until the scanning has completed.
-  while (is_scanning.load())
-    std::this_thread::sleep_for(std::chrono::milliseconds(100));
-}
-
-void IncludeComplete::rescan() {
-  if (is_scanning || LLVM_VERSION_MAJOR >= 8)
-    return;
-
-  completion_items.clear();
-  absolute_path_to_completion_item.clear();
-  inserted_paths.clear();
-
-  if (!match_ && (g_config->completion.include.whitelist.size() ||
-                  g_config->completion.include.blacklist.size()))
-    match_ =
-        std::make_unique<GroupMatch>(g_config->completion.include.whitelist,
-                                     g_config->completion.include.blacklist);
-
-  is_scanning = true;
-  std::thread([this]() {
-    set_thread_name("include");
-    for (auto &[root, folder] : project_->root2folder) {
-      for (auto &search_kind : folder.search_dir2kind) {
-        const std::string &search = search_kind.first;
-        int kind = search_kind.second;
-        assert(search.back() == '/');
-        if (match_ && !match_->matches(search))
-          return;
-        bool include_cpp = search.find("include/c++") != std::string::npos;
-
-        std::vector<CompletionCandidate> results;
-        getFilesInFolder(
-            search, true /*recursive*/, false /*add_folder_to_path*/,
-            [&](const std::string &path) {
-              bool ok = include_cpp;
-              for (StringRef suffix :
-                   g_config->completion.include.suffixWhitelist)
-                if (StringRef(path).endswith(suffix))
-                  ok = true;
-              if (!ok)
-                return;
-              if (match_ && !match_->matches(search + path))
-                return;
-
-              CompletionCandidate candidate;
-              candidate.absolute_path = search + path;
-              candidate.completion_item = buildCompletionItem(path, kind);
-              results.push_back(candidate);
-            });
-
-        std::lock_guard lock(completion_items_mutex);
-        for (CompletionCandidate &result : results)
-          insertCompletionItem(result.absolute_path,
-                               std::move(result.completion_item));
-      }
-    }
-
-    is_scanning = false;
-  }).detach();
-}
-
-void IncludeComplete::insertCompletionItem(const std::string &absolute_path,
-                                           CompletionItem &&item) {
-  if (inserted_paths.try_emplace(item.detail, inserted_paths.size()).second) {
-    completion_items.push_back(item);
-    // insert if not found or with shorter include path
-    auto it = absolute_path_to_completion_item.find(absolute_path);
-    if (it == absolute_path_to_completion_item.end() ||
-        completion_items[it->second].detail.length() > item.detail.length()) {
-      absolute_path_to_completion_item[absolute_path] =
-          completion_items.size() - 1;
-    }
-  }
-}
-
-void IncludeComplete::addFile(const std::string &path) {
-  bool ok = false;
-  for (StringRef suffix : g_config->completion.include.suffixWhitelist)
-    if (StringRef(path).endswith(suffix))
-      ok = true;
-  if (!ok)
-    return;
-  if (match_ && !match_->matches(path))
-    return;
-
-  std::string trimmed_path = path;
-  int kind = trimPath(project_, trimmed_path);
-  CompletionItem item = buildCompletionItem(trimmed_path, kind);
-
-  std::unique_lock<std::mutex> lock(completion_items_mutex, std::defer_lock);
-  if (is_scanning)
-    lock.lock();
-  insertCompletionItem(path, std::move(item));
-}
-
-std::optional<CompletionItem>
-IncludeComplete::findCompletionItemForAbsolutePath(
-    const std::string &absolute_path) {
-  std::lock_guard<std::mutex> lock(completion_items_mutex);
-
-  auto it = absolute_path_to_completion_item.find(absolute_path);
-  if (it == absolute_path_to_completion_item.end())
-    return std::nullopt;
-  return completion_items[it->second];
-}
-} // namespace ccls
diff --git a/src/include_complete.hh b/src/include_complete.hh
deleted file mode 100644
index 49521f75..00000000
--- a/src/include_complete.hh
+++ /dev/null
@@ -1,49 +0,0 @@
-// Copyright 2017-2018 ccls Authors
-// SPDX-License-Identifier: Apache-2.0
-
-#pragma once
-
-#include "message_handler.hh"
-
-#include <atomic>
-#include <mutex>
-
-namespace ccls {
-struct GroupMatch;
-struct Project;
-
-struct IncludeComplete {
-  IncludeComplete(Project *project);
-  ~IncludeComplete();
-
-  // Starts scanning directories. Clears existing cache.
-  void rescan();
-
-  // Ensures the one-off file is inside |completion_items|.
-  void addFile(const std::string &absolute_path);
-
-  std::optional<ccls::CompletionItem>
-  findCompletionItemForAbsolutePath(const std::string &absolute_path);
-
-  // Insert item to |completion_items|.
-  // Update |absolute_path_to_completion_item| and |inserted_paths|.
-  void insertCompletionItem(const std::string &absolute_path,
-                            ccls::CompletionItem &&item);
-
-  // Guards |completion_items| when |is_scanning| is true.
-  std::mutex completion_items_mutex;
-  std::atomic<bool> is_scanning;
-  std::vector<ccls::CompletionItem> completion_items;
-
-  // Absolute file path to the completion item in |completion_items|.
-  // Keep the one with shortest include path.
-  std::unordered_map<std::string, int> absolute_path_to_completion_item;
-
-  // Only one completion item per include path.
-  std::unordered_map<std::string, int> inserted_paths;
-
-  // Cached references
-  Project *project_;
-  std::unique_ptr<GroupMatch> match_;
-};
-} // namespace ccls
diff --git a/src/indexer.cc b/src/indexer.cc
index 8f84bc02..b81f1d9f 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -710,9 +710,6 @@ public:
 public:
   IndexDataConsumer(IndexParam &param) : param(param) {}
   void initialize(ASTContext &ctx) override { this->ctx = param.ctx = &ctx; }
-#if LLVM_VERSION_MAJOR < 10 // llvmorg-10-init-12036-g3b9715cb219
-# define handleDeclOccurrence handleDeclOccurence
-#endif
   bool handleDeclOccurrence(const Decl *d, index::SymbolRoleSet roles,
                             ArrayRef<index::SymbolRelation> relations,
                             SourceLocation src_loc,
@@ -899,31 +896,6 @@ public:
             if (!isa<EnumConstantDecl>(d))
               db->toType(usr1).instances.push_back(usr);
           } else if (const Decl *d1 = getAdjustedDecl(getTypeDecl(t))) {
-#if LLVM_VERSION_MAJOR < 9
-            if (isa<TemplateTypeParmDecl>(d1)) {
-              // e.g. TemplateTypeParmDecl is not handled by
-              // handleDeclOccurence.
-              SourceRange sr1 = d1->getSourceRange();
-              if (sm.getFileID(sr1.getBegin()) == fid) {
-                IndexParam::DeclInfo *info1;
-                Usr usr1 = getUsr(d1, &info1);
-                IndexType &type1 = db->toType(usr1);
-                SourceLocation sl1 = d1->getLocation();
-                type1.def.spell = {
-                    Use{{fromTokenRange(sm, lang, {sl1, sl1}), Role::Definition},
-                        lid},
-                    fromTokenRange(sm, lang, sr1)};
-                type1.def.detailed_name = intern(info1->short_name);
-                type1.def.short_name_size = int16_t(info1->short_name.size());
-                type1.def.kind = SymbolKind::TypeParameter;
-                type1.def.parent_kind = SymbolKind::Class;
-                var->def.type = usr1;
-                type1.instances.push_back(usr);
-                break;
-              }
-            }
-#endif
-
             IndexParam::DeclInfo *info1;
             Usr usr1 = getUsr(d1, &info1);
             var->def.type = usr1;
@@ -1237,10 +1209,8 @@ public:
         std::make_unique<IndexPPCallbacks>(pp->getSourceManager(), param));
     std::vector<std::unique_ptr<ASTConsumer>> consumers;
     consumers.push_back(std::make_unique<SkipProcessed>(param));
-#if LLVM_VERSION_MAJOR >= 10 // rC370337
     consumers.push_back(index::createIndexingASTConsumer(
         dataConsumer, indexOpts, std::move(pp)));
-#endif
     return std::make_unique<MultiplexConsumer>(std::move(consumers));
   }
 };
@@ -1349,12 +1319,7 @@ index(SemaManager *manager, WorkingFiles *wfiles, VFS *vfs,
   if (!clang->hasTarget())
     return {};
   clang->getPreprocessorOpts().RetainRemappedFileBuffers = true;
-#if LLVM_VERSION_MAJOR >= 9 // rC357037
   clang->createFileManager(fs);
-#else
-  clang->setVirtualFileSystem(fs);
-  clang->createFileManager();
-#endif
   clang->setSourceManager(new SourceManager(clang->getDiagnostics(),
                                             clang->getFileManager(), true));
 
@@ -1366,39 +1331,23 @@ index(SemaManager *manager, WorkingFiles *wfiles, VFS *vfs,
   if (no_linkage) {
     indexOpts.IndexFunctionLocals = true;
     indexOpts.IndexImplicitInstantiation = true;
-#if LLVM_VERSION_MAJOR >= 9
-
     indexOpts.IndexParametersInDeclarations =
         g_config->index.parametersInDeclarations;
     indexOpts.IndexTemplateParameters = true;
-#endif
   }
 
-#if LLVM_VERSION_MAJOR >= 10 // rC370337
   auto action = std::make_unique<IndexFrontendAction>(
       std::make_shared<IndexDataConsumer>(param), indexOpts, param);
-#else
-  auto dataConsumer = std::make_shared<IndexDataConsumer>(param);
-  auto action = createIndexingAction(
-      dataConsumer, indexOpts,
-      std::make_unique<IndexFrontendAction>(dataConsumer, indexOpts, param));
-#endif
-
   std::string reason;
   {
     llvm::CrashRecoveryContext crc;
     auto parse = [&]() {
       if (!action->BeginSourceFile(*clang, clang->getFrontendOpts().Inputs[0]))
         return;
-#if LLVM_VERSION_MAJOR >= 9 // rL364464
       if (llvm::Error e = action->Execute()) {
         reason = llvm::toString(std::move(e));
         return;
       }
-#else
-      if (!action->Execute())
-        return;
-#endif
       action->EndSourceFile();
       ok = true;
     };
diff --git a/src/message_handler.hh b/src/message_handler.hh
index a5833fee..d2f66c93 100644
--- a/src/message_handler.hh
+++ b/src/message_handler.hh
@@ -14,7 +14,6 @@
 namespace ccls {
 struct SemaManager;
 struct VFS;
-struct IncludeComplete;
 struct Project;
 struct WorkingFile;
 struct WorkingFiles;
@@ -239,7 +238,6 @@ struct ReplyOnce {
 struct MessageHandler {
   SemaManager *manager = nullptr;
   DB *db = nullptr;
-  IncludeComplete *include_complete = nullptr;
   Project *project = nullptr;
   VFS *vfs = nullptr;
   WorkingFiles *wfiles = nullptr;
diff --git a/src/messages/initialize.cc b/src/messages/initialize.cc
index e7a71d54..cae1ca82 100644
--- a/src/messages/initialize.cc
+++ b/src/messages/initialize.cc
@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: Apache-2.0
 
 #include "filesystem.hh"
-#include "include_complete.hh"
 #include "log.hh"
 #include "message_handler.hh"
 #include "pipeline.hh"
@@ -261,7 +260,7 @@ void *indexer(void *arg_) {
   // Don't lower priority on __APPLE__. getpriority(2) says "When setting a
   // thread into background state the scheduling priority is set to lowest
   // value, disk and network IO are throttled."
-#if LLVM_ENABLE_THREADS && LLVM_VERSION_MAJOR >= 9 && !defined(__APPLE__)
+#if LLVM_ENABLE_THREADS && !defined(__APPLE__)
   set_thread_priority(ThreadPriority::Background);
 #endif
   pipeline::indexer_Main(h->manager, h->vfs, h->project, h->wfiles);
@@ -389,10 +388,6 @@ void do_initialize(MessageHandler *m, InitializeParam &param,
   for (int i = 0; i < g_config->index.threads; i++)
     spawnThread(indexer, new std::pair<MessageHandler *, int>{m, i});
 
-  // Start scanning include directories before dispatching project
-  // files, because that takes a long time.
-  m->include_complete->rescan();
-
   LOG_S(INFO) << "dispatch initial index requests";
   m->project->index(m->wfiles, reply.id);
 
diff --git a/src/messages/textDocument_completion.cc b/src/messages/textDocument_completion.cc
index ce769d4d..10cf96b6 100644
--- a/src/messages/textDocument_completion.cc
+++ b/src/messages/textDocument_completion.cc
@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: Apache-2.0
 
 #include "fuzzy_match.hh"
-#include "include_complete.hh"
 #include "log.hh"
 #include "message_handler.hh"
 #include "pipeline.hh"
@@ -13,10 +12,6 @@
 #include <clang/Sema/Sema.h>
 #include <llvm/ADT/Twine.h>
 
-#if LLVM_VERSION_MAJOR < 8
-#include <regex>
-#endif
-
 #if LLVM_VERSION_MAJOR >= 18 // llvmorg-18-init-10631-gedd690b02e16
 #define TTK_Struct TagTypeKind::Struct
 #endif
@@ -52,54 +47,6 @@ struct CompletionList {
 };
 REFLECT_STRUCT(CompletionList, isIncomplete, items);
 
-#if LLVM_VERSION_MAJOR < 8
-void decorateIncludePaths(const std::smatch &match,
-                          std::vector<CompletionItem> *items, char quote) {
-  std::string spaces_after_include = " ";
-  if (match[3].compare("include") == 0 && quote != '\0')
-    spaces_after_include = match[4].str();
-
-  std::string prefix =
-      match[1].str() + '#' + match[2].str() + "include" + spaces_after_include;
-  std::string suffix = match[7].str();
-
-  for (CompletionItem &item : *items) {
-    char quote0, quote1;
-    if (quote != '"')
-      quote0 = '<', quote1 = '>';
-    else
-      quote0 = quote1 = '"';
-
-    item.textEdit.newText =
-        prefix + quote0 + item.textEdit.newText + quote1 + suffix;
-    item.label = prefix + quote0 + item.label + quote1 + suffix;
-  }
-}
-
-struct ParseIncludeLineResult {
-  bool ok;
-  std::string keyword;
-  std::string quote;
-  std::string pattern;
-  std::smatch match;
-};
-
-ParseIncludeLineResult ParseIncludeLine(const std::string &line) {
-  static const std::regex pattern("(\\s*)"       // [1]: spaces before '#'
-                                  "#"            //
-                                  "(\\s*)"       // [2]: spaces after '#'
-                                  "([^\\s\"<]*)" // [3]: "include"
-                                  "(\\s*)"       // [4]: spaces before quote
-                                  "([\"<])?"     // [5]: the first quote char
-                                  "([^\\s\">]*)" // [6]: path of file
-                                  "[\">]?"       //
-                                  "(.*)");       // [7]: suffix after quote char
-  std::smatch match;
-  bool ok = std::regex_match(line, match, pattern);
-  return {ok, match[3], match[5], match[6], match};
-}
-#endif
-
 // Pre-filters completion responses before sending to vscode. This results in a
 // significantly snappier completion experience as vscode is easily overloaded
 // when given 1000+ completion items.
@@ -309,10 +256,8 @@ CompletionItemKind getCompletionKind(CodeCompletionContext::Kind k,
   case CodeCompletionResult::RK_Macro:
     return CompletionItemKind::Reference;
   case CodeCompletionResult::RK_Pattern:
-#if LLVM_VERSION_MAJOR >= 8
     if (k == CodeCompletionContext::CCC_IncludedFile)
       return CompletionItemKind::File;
-#endif
     return CompletionItemKind::Snippet;
   }
 }
@@ -402,11 +347,7 @@ public:
 
   CompletionConsumer(const CodeCompleteOptions &opts, bool from_cache)
       :
-#if LLVM_VERSION_MAJOR >= 9 // rC358696
         CodeCompleteConsumer(opts),
-#else
-        CodeCompleteConsumer(opts, false),
-#endif
         alloc(std::make_shared<clang::GlobalCodeCompletionAllocator>()),
         cctu_info(alloc), from_cache(from_cache) {
   }
@@ -544,31 +485,6 @@ void MessageHandler::textDocument_completion(CompletionParam &param,
   Position end_pos = param.position;
   Position begin_pos = wf->getCompletionPosition(param.position, &filter);
 
-#if LLVM_VERSION_MAJOR < 8
-  ParseIncludeLineResult preprocess = ParseIncludeLine(buffer_line);
-  if (preprocess.ok && preprocess.keyword.compare("include") == 0) {
-    CompletionList result;
-    char quote = std::string(preprocess.match[5])[0];
-    {
-      std::unique_lock<std::mutex> lock(
-          include_complete->completion_items_mutex, std::defer_lock);
-      if (include_complete->is_scanning)
-        lock.lock();
-      for (auto &item : include_complete->completion_items)
-        if (quote == '\0' || (item.quote_kind_ & 1 && quote == '"') ||
-            (item.quote_kind_ & 2 && quote == '<'))
-          result.items.push_back(item);
-    }
-    begin_pos.character = 0;
-    end_pos.character = (int)buffer_line.size();
-    filterCandidates(result, preprocess.pattern, begin_pos, end_pos,
-                     buffer_line);
-    decorateIncludePaths(preprocess.match, &result.items, quote);
-    reply(result);
-    return;
-  }
-#endif
-
   SemaManager::OnComplete callback =
       [filter, path, begin_pos, end_pos, reply,
        buffer_line](CodeCompleteConsumer *optConsumer) {
diff --git a/src/messages/textDocument_did.cc b/src/messages/textDocument_did.cc
index f9d10815..00339d16 100644
--- a/src/messages/textDocument_did.cc
+++ b/src/messages/textDocument_did.cc
@@ -1,7 +1,6 @@
 // Copyright 2017-2018 ccls Authors
 // SPDX-License-Identifier: Apache-2.0
 
-#include "include_complete.hh"
 #include "message_handler.hh"
 #include "pipeline.hh"
 #include "project.hh"
@@ -38,7 +37,6 @@ void MessageHandler::textDocument_didOpen(DidOpenTextDocumentParam &param) {
     emitSkippedRanges(wf, *file);
     emitSemanticHighlight(db, wf, *file);
   }
-  include_complete->addFile(wf->filename);
 
   // Submit new index request if it is not a header file or there is no
   // pending index request.
diff --git a/src/messages/textDocument_signatureHelp.cc b/src/messages/textDocument_signatureHelp.cc
index 4192272a..10cdcddf 100644
--- a/src/messages/textDocument_signatureHelp.cc
+++ b/src/messages/textDocument_signatureHelp.cc
@@ -65,22 +65,10 @@ public:
   bool from_cache;
   SignatureHelp ls_sighelp;
   SignatureHelpConsumer(const clang::CodeCompleteOptions &opts, bool from_cache)
-      :
-#if LLVM_VERSION_MAJOR >= 9 // rC358696
-        CodeCompleteConsumer(opts),
-#else
-        CodeCompleteConsumer(opts, false),
-#endif
-        alloc(std::make_shared<GlobalCodeCompletionAllocator>()),
-        cCTUInfo(alloc), from_cache(from_cache) {
-  }
-  void ProcessOverloadCandidates(Sema &s, unsigned currentArg,
-                                 OverloadCandidate *candidates,
-                                 unsigned numCandidates
-#if LLVM_VERSION_MAJOR >= 8
-                                 ,
+      : CodeCompleteConsumer(opts), alloc(std::make_shared<GlobalCodeCompletionAllocator>()), cCTUInfo(alloc),
+        from_cache(from_cache) {}
+  void ProcessOverloadCandidates(Sema &s, unsigned currentArg, OverloadCandidate *candidates, unsigned numCandidates,
                                  SourceLocation openParLoc
-#endif
 #if LLVM_VERSION_MAJOR >= 14
                                  ,
                                  bool braced
diff --git a/src/pipeline.cc b/src/pipeline.cc
index cf483e50..f63d5b9a 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -4,7 +4,6 @@
 #include "pipeline.hh"
 
 #include "config.hh"
-#include "include_complete.hh"
 #include "log.hh"
 #include "lsp.hh"
 #include "message_handler.hh"
@@ -657,7 +656,6 @@ void mainLoop() {
         }
       });
 
-  IncludeComplete include_complete(&project);
   DB db;
 
   // Setup shared references.
@@ -667,7 +665,6 @@ void mainLoop() {
   handler.vfs = &vfs;
   handler.wfiles = &wfiles;
   handler.manager = &manager;
-  handler.include_complete = &include_complete;
 
   bool work_done_created = false, in_progress = false;
   bool has_indexed = false;
@@ -787,14 +784,12 @@ void standalone(const std::string &root) {
       nullptr, nullptr,
       [](const std::string &, const std::vector<Diagnostic> &) {},
       [](const RequestId &id) {});
-  IncludeComplete complete(&project);
 
   MessageHandler handler;
   handler.project = &project;
   handler.wfiles = &wfiles;
   handler.vfs = &vfs;
   handler.manager = &manager;
-  handler.include_complete = &complete;
 
   standaloneInitialize(handler, root);
   bool tty = sys::Process::StandardOutIsDisplayed();
diff --git a/src/project.cc b/src/project.cc
index b1b7f557..6910a4be 100644
--- a/src/project.cc
+++ b/src/project.cc
@@ -134,88 +134,6 @@ struct ProjectProcessor {
       }
     }
     entry.args = args;
-    getSearchDirs(entry);
-  }
-
-  void getSearchDirs(Project::Entry &entry) {
-#if LLVM_VERSION_MAJOR < 8
-    const std::string base_name = sys::path::filename(entry.filename);
-    size_t hash = std::hash<std::string>{}(entry.directory);
-    bool OPT_o = false;
-    for (auto &arg : entry.args) {
-      bool last_o = OPT_o;
-      OPT_o = false;
-      if (arg[0] == '-') {
-        OPT_o = arg[1] == 'o' && arg[2] == '\0';
-        if (OPT_o || arg[1] == 'D' || arg[1] == 'W')
-          continue;
-      } else if (last_o) {
-        continue;
-      } else if (sys::path::filename(arg) == base_name) {
-        LanguageId lang = lookupExtension(arg).first;
-        if (lang != LanguageId::Unknown) {
-          hash_combine(hash, (size_t)lang);
-          continue;
-        }
-      }
-      hash_combine(hash, std::hash<std::string_view>{}(arg));
-    }
-    if (!command_set.insert(hash).second)
-      return;
-    auto args = entry.args;
-    args.push_back("-fsyntax-only");
-    for (const std::string &arg : g_config->clang.extraArgs)
-      args.push_back(intern(arg));
-    args.push_back(intern("-working-directory=" + entry.directory));
-    args.push_back(intern("-resource-dir=" + g_config->clang.resourceDir));
-
-    // a weird C++ deduction guide heap-use-after-free causes libclang to crash.
-    IgnoringDiagConsumer DiagC;
-    IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts(new DiagnosticOptions());
-    DiagnosticsEngine Diags(
-        IntrusiveRefCntPtr<DiagnosticIDs>(new DiagnosticIDs()), &*DiagOpts,
-        &DiagC, false);
-
-    driver::Driver Driver(args[0], llvm::sys::getDefaultTargetTriple(), Diags);
-    auto TargetAndMode =
-        driver::ToolChain::getTargetAndModeFromProgramName(args[0]);
-    if (!TargetAndMode.TargetPrefix.empty()) {
-      const char *arr[] = {"-target", TargetAndMode.TargetPrefix.c_str()};
-      args.insert(args.begin() + 1, std::begin(arr), std::end(arr));
-      Driver.setTargetAndMode(TargetAndMode);
-    }
-    Driver.setCheckInputsExist(false);
-
-    std::unique_ptr<driver::Compilation> C(Driver.BuildCompilation(args));
-    const driver::JobList &Jobs = C->getJobs();
-    if (Jobs.size() != 1)
-      return;
-    const auto &CCArgs = Jobs.begin()->getArguments();
-
-    auto CI = std::make_unique<CompilerInvocation>();
-    CompilerInvocation::CreateFromArgs(*CI, CCArgs.data(),
-                                       CCArgs.data() + CCArgs.size(), Diags);
-    CI->getFrontendOpts().DisableFree = false;
-    CI->getCodeGenOpts().DisableFree = false;
-
-    HeaderSearchOptions &HeaderOpts = CI->getHeaderSearchOpts();
-    for (auto &E : HeaderOpts.UserEntries) {
-      std::string path =
-          normalizePath(resolveIfRelative(entry.directory, E.Path));
-      ensureEndsInSlash(path);
-      switch (E.Group) {
-      default:
-        folder.search_dir2kind[path] |= 2;
-        break;
-      case frontend::Quoted:
-        folder.search_dir2kind[path] |= 1;
-        break;
-      case frontend::Angled:
-        folder.search_dir2kind[path] |= 3;
-        break;
-      }
-    }
-#endif
   }
 };
 
@@ -452,7 +370,6 @@ void Project::loadDirectory(const std::string &root, Project::Folder &folder) {
           entry.args.push_back(intern(args[i]));
       }
       entry.compdb_size = entry.args.size();
-      proc.getSearchDirs(entry);
       if (seen.insert(entry.filename).second)
         folder.entries.push_back(entry);
     }
diff --git a/src/sema_manager.cc b/src/sema_manager.cc
index 0a7f6eb8..bf806e47 100644
--- a/src/sema_manager.cc
+++ b/src/sema_manager.cc
@@ -26,39 +26,6 @@ using namespace llvm;
 #include <thread>
 namespace chrono = std::chrono;
 
-#if LLVM_VERSION_MAJOR < 8
-namespace clang::vfs {
-struct ProxyFileSystem : FileSystem {
-  explicit ProxyFileSystem(IntrusiveRefCntPtr<FileSystem> FS)
-      : FS(std::move(FS)) {}
-  llvm::ErrorOr<Status> status(const Twine &Path) override {
-    return FS->status(Path);
-  }
-  llvm::ErrorOr<std::unique_ptr<File>>
-  openFileForRead(const Twine &Path) override {
-    return FS->openFileForRead(Path);
-  }
-  directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override {
-    return FS->dir_begin(Dir, EC);
-  }
-  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
-    return FS->getCurrentWorkingDirectory();
-  }
-  std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
-    return FS->setCurrentWorkingDirectory(Path);
-  }
-#if LLVM_VERSION_MAJOR == 7
-  std::error_code getRealPath(const Twine &Path,
-                              SmallVectorImpl<char> &Output) const override {
-    return FS->getRealPath(Path, Output);
-  }
-#endif
-  FileSystem &getUnderlyingFS() { return *FS; }
-  IntrusiveRefCntPtr<FileSystem> FS;
-};
-} // namespace clang::vfs
-#endif
-
 namespace ccls {
 
 TextEdit toTextEdit(const clang::SourceManager &sm, const clang::LangOptions &l,
@@ -330,12 +297,7 @@ buildCompilerInstance(Session &session, std::unique_ptr<CompilerInvocation> ci,
   // Construct SourceManager with UserFilesAreVolatile: true because otherwise
   // RequiresNullTerminator: true may cause out-of-bounds read when a file is
   // mmap'ed but is saved concurrently.
-#if LLVM_VERSION_MAJOR >= 9 // rC357037
   clang->createFileManager(fs);
-#else
-  clang->setVirtualFileSystem(fs);
-  clang->createFileManager();
-#endif
   clang->setSourceManager(new SourceManager(clang->getDiagnostics(),
                                             clang->getFileManager(), true));
   auto &isec = clang->getFrontendOpts().Inputs;
@@ -353,15 +315,10 @@ bool parse(CompilerInstance &clang) {
   auto run = [&]() {
     if (!action.BeginSourceFile(clang, clang.getFrontendOpts().Inputs[0]))
       return;
-#if LLVM_VERSION_MAJOR >= 9 // rL364464
     if (llvm::Error e = action.Execute()) {
       llvm::consumeError(std::move(e));
       return;
     }
-#else
-    if (!action.Execute())
-      return;
-#endif
     action.EndSourceFile();
     ok = true;
   };