Imported Upstream version 5.18.0.207

Former-commit-id: 3b152f462918d427ce18620a2cbe4f8b79650449

external/llvm/lib/Support/TrigramIndex.cpp

@@ -1,111 +0,0 @@
-//===-- TrigramIndex.cpp - a heuristic for SpecialCaseList ----------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// TrigramIndex implements a heuristic for SpecialCaseList that allows to
-// filter out ~99% incoming queries when all regular expressions in the
-// SpecialCaseList are simple wildcards with '*' and '.'. If rules are more
-// complicated, the check is defeated and it will always pass the queries to a
-// full regex.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Support/TrigramIndex.h"
-#include "llvm/ADT/SmallVector.h"
-
-#include <set>
-#include <string>
-#include <unordered_map>
-
-using namespace llvm;
-
-static const char RegexAdvancedMetachars[] = "()^$|+?[]\\{}";
-
-static bool isAdvancedMetachar(unsigned Char) {
-  return strchr(RegexAdvancedMetachars, Char) != nullptr;
-}
-
-void TrigramIndex::insert(std::string Regex) {
-  if (Defeated) return;
-  std::set<unsigned> Was;
-  unsigned Cnt = 0;
-  unsigned Tri = 0;
-  unsigned Len = 0;
-  bool Escaped = false;
-  for (unsigned Char : Regex) {
-    if (!Escaped) {
-      // Regular expressions allow escaping symbols by preceding it with '\'.
-      if (Char == '\\') {
-        Escaped = true;
-        continue;
-      }
-      if (isAdvancedMetachar(Char)) {
-        // This is a more complicated regex than we can handle here.
-        Defeated = true;
-        return;
-      }
-      if (Char == '.' || Char == '*') {
-        Tri = 0;
-        Len = 0;
-        continue;
-      }
-    }
-    if (Escaped && Char >= '1' && Char <= '9') {
-      Defeated = true;
-      return;
-    }
-    // We have already handled escaping and can reset the flag.
-    Escaped = false;
-    Tri = ((Tri << 8) + Char) & 0xFFFFFF;
-    Len++;
-    if (Len < 3)
-      continue;
-    // We don't want the index to grow too much for the popular trigrams,
-    // as they are weak signals. It's ok to still require them for the
-    // rules we have already processed. It's just a small additional
-    // computational cost.
-    if (Index[Tri].size() >= 4)
-      continue;
-    Cnt++;
-    if (!Was.count(Tri)) {
-      // Adding the current rule to the index.
-      Index[Tri].push_back(Counts.size());
-      Was.insert(Tri);
-    }
-  }
-  if (!Cnt) {
-    // This rule does not have remarkable trigrams to rely on.
-    // We have to always call the full regex chain.
-    Defeated = true;
-    return;
-  }
-  Counts.push_back(Cnt);
-}
-
-bool TrigramIndex::isDefinitelyOut(StringRef Query) const {
-  if (Defeated)
-    return false;
-  std::vector<unsigned> CurCounts(Counts.size());
-  unsigned Tri = 0;
-  for (size_t I = 0; I < Query.size(); I++) {
-    Tri = ((Tri << 8) + Query[I]) & 0xFFFFFF;
-    if (I < 2)
-      continue;
-    const auto &II = Index.find(Tri);
-    if (II == Index.end())
-      continue;
-    for (size_t J : II->second) {
-      CurCounts[J]++;
-      // If we have reached a desired limit, we have to look at the query
-      // more closely by running a full regex.
-      if (CurCounts[J] >= Counts[J])
-        return false;
-    }
-  }
-  return true;
-}