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diff --git a/contrib/llvm-project/llvm/lib/LineEditor/LineEditor.cpp b/contrib/llvm-project/llvm/lib/LineEditor/LineEditor.cpp
new file mode 100644
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+++ b/contrib/llvm-project/llvm/lib/LineEditor/LineEditor.cpp
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+//===-- LineEditor.cpp - line editor --------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LineEditor/LineEditor.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Config/config.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <cstdio>
+#ifdef HAVE_LIBEDIT
+#include <histedit.h>
+#endif
+
+using namespace llvm;
+
+std::string LineEditor::getDefaultHistoryPath(StringRef ProgName) {
+  SmallString<32> Path;
+  if (sys::path::home_directory(Path)) {
+    sys::path::append(Path, "." + ProgName + "-history");
+    return std::string(Path.str());
+  }
+  return std::string();
+}
+
+LineEditor::CompleterConcept::~CompleterConcept() {}
+LineEditor::ListCompleterConcept::~ListCompleterConcept() {}
+
+std::string LineEditor::ListCompleterConcept::getCommonPrefix(
+    const std::vector<Completion> &Comps) {
+  assert(!Comps.empty());
+
+  std::string CommonPrefix = Comps[0].TypedText;
+  for (std::vector<Completion>::const_iterator I = Comps.begin() + 1,
+                                               E = Comps.end();
+       I != E; ++I) {
+    size_t Len = std::min(CommonPrefix.size(), I->TypedText.size());
+    size_t CommonLen = 0;
+    for (; CommonLen != Len; ++CommonLen) {
+      if (CommonPrefix[CommonLen] != I->TypedText[CommonLen])
+        break;
+    }
+    CommonPrefix.resize(CommonLen);
+  }
+  return CommonPrefix;
+}
+
+LineEditor::CompletionAction
+LineEditor::ListCompleterConcept::complete(StringRef Buffer, size_t Pos) const {
+  CompletionAction Action;
+  std::vector<Completion> Comps = getCompletions(Buffer, Pos);
+  if (Comps.empty()) {
+    Action.Kind = CompletionAction::AK_ShowCompletions;
+    return Action;
+  }
+
+  std::string CommonPrefix = getCommonPrefix(Comps);
+
+  // If the common prefix is non-empty we can simply insert it. If there is a
+  // single completion, this will insert the full completion. If there is more
+  // than one, this might be enough information to jog the user's memory but if
+  // not the user can also hit tab again to see the completions because the
+  // common prefix will then be empty.
+  if (CommonPrefix.empty()) {
+    Action.Kind = CompletionAction::AK_ShowCompletions;
+    for (std::vector<Completion>::iterator I = Comps.begin(), E = Comps.end();
+         I != E; ++I)
+      Action.Completions.push_back(I->DisplayText);
+  } else {
+    Action.Kind = CompletionAction::AK_Insert;
+    Action.Text = CommonPrefix;
+  }
+
+  return Action;
+}
+
+LineEditor::CompletionAction LineEditor::getCompletionAction(StringRef Buffer,
+                                                             size_t Pos) const {
+  if (!Completer) {
+    CompletionAction Action;
+    Action.Kind = CompletionAction::AK_ShowCompletions;
+    return Action;
+  }
+
+  return Completer->complete(Buffer, Pos);
+}
+
+#ifdef HAVE_LIBEDIT
+
+// libedit-based implementation.
+
+struct LineEditor::InternalData {
+  LineEditor *LE;
+
+  History *Hist;
+  EditLine *EL;
+
+  unsigned PrevCount;
+  std::string ContinuationOutput;
+
+  FILE *Out;
+};
+
+namespace {
+
+const char *ElGetPromptFn(EditLine *EL) {
+  LineEditor::InternalData *Data;
+  if (el_get(EL, EL_CLIENTDATA, &Data) == 0)
+    return Data->LE->getPrompt().c_str();
+  return "> ";
+}
+
+// Handles tab completion.
+//
+// This function is really horrible. But since the alternative is to get into
+// the line editor business, here we are.
+unsigned char ElCompletionFn(EditLine *EL, int ch) {
+  LineEditor::InternalData *Data;
+  if (el_get(EL, EL_CLIENTDATA, &Data) == 0) {
+    if (!Data->ContinuationOutput.empty()) {
+      // This is the continuation of the AK_ShowCompletions branch below.
+      FILE *Out = Data->Out;
+
+      // Print the required output (see below).
+      ::fwrite(Data->ContinuationOutput.c_str(),
+               Data->ContinuationOutput.size(), 1, Out);
+
+      // Push a sequence of Ctrl-B characters to move the cursor back to its
+      // original position.
+      std::string Prevs(Data->PrevCount, '\02');
+      ::el_push(EL, const_cast<char *>(Prevs.c_str()));
+
+      Data->ContinuationOutput.clear();
+
+      return CC_REFRESH;
+    }
+
+    const LineInfo *LI = ::el_line(EL);
+    LineEditor::CompletionAction Action = Data->LE->getCompletionAction(
+        StringRef(LI->buffer, LI->lastchar - LI->buffer),
+        LI->cursor - LI->buffer);
+    switch (Action.Kind) {
+    case LineEditor::CompletionAction::AK_Insert:
+      ::el_insertstr(EL, Action.Text.c_str());
+      return CC_REFRESH;
+
+    case LineEditor::CompletionAction::AK_ShowCompletions:
+      if (Action.Completions.empty()) {
+        return CC_REFRESH_BEEP;
+      } else {
+        // Push a Ctrl-E and a tab. The Ctrl-E causes libedit to move the cursor
+        // to the end of the line, so that when we emit a newline we will be on
+        // a new blank line. The tab causes libedit to call this function again
+        // after moving the cursor. There doesn't seem to be anything we can do
+        // from here to cause libedit to move the cursor immediately. This will
+        // break horribly if the user has rebound their keys, so for now we do
+        // not permit user rebinding.
+        ::el_push(EL, const_cast<char *>("\05\t"));
+
+        // This assembles the output for the continuation block above.
+        raw_string_ostream OS(Data->ContinuationOutput);
+
+        // Move cursor to a blank line.
+        OS << "\n";
+
+        // Emit the completions.
+        for (std::vector<std::string>::iterator I = Action.Completions.begin(),
+                                                E = Action.Completions.end();
+             I != E; ++I) {
+          OS << *I << "\n";
+        }
+
+        // Fool libedit into thinking nothing has changed. Reprint its prompt
+        // and the user input. Note that the cursor will remain at the end of
+        // the line after this.
+        OS << Data->LE->getPrompt()
+           << StringRef(LI->buffer, LI->lastchar - LI->buffer);
+
+        // This is the number of characters we need to tell libedit to go back:
+        // the distance between end of line and the original cursor position.
+        Data->PrevCount = LI->lastchar - LI->cursor;
+
+        return CC_REFRESH;
+      }
+    }
+  }
+  return CC_ERROR;
+}
+
+} // end anonymous namespace
+
+LineEditor::LineEditor(StringRef ProgName, StringRef HistoryPath, FILE *In,
+                       FILE *Out, FILE *Err)
+    : Prompt((ProgName + "> ").str()), HistoryPath(std::string(HistoryPath)),
+      Data(new InternalData) {
+  if (HistoryPath.empty())
+    this->HistoryPath = getDefaultHistoryPath(ProgName);
+
+  Data->LE = this;
+  Data->Out = Out;
+
+  Data->Hist = ::history_init();
+  assert(Data->Hist);
+
+  Data->EL = ::el_init(ProgName.str().c_str(), In, Out, Err);
+  assert(Data->EL);
+
+  ::el_set(Data->EL, EL_PROMPT, ElGetPromptFn);
+  ::el_set(Data->EL, EL_EDITOR, "emacs");
+  ::el_set(Data->EL, EL_HIST, history, Data->Hist);
+  ::el_set(Data->EL, EL_ADDFN, "tab_complete", "Tab completion function",
+           ElCompletionFn);
+  ::el_set(Data->EL, EL_BIND, "\t", "tab_complete", NULL);
+  ::el_set(Data->EL, EL_BIND, "^r", "em-inc-search-prev",
+           NULL); // Cycle through backwards search, entering string
+  ::el_set(Data->EL, EL_BIND, "^w", "ed-delete-prev-word",
+           NULL); // Delete previous word, behave like bash does.
+  ::el_set(Data->EL, EL_BIND, "\033[3~", "ed-delete-next-char",
+           NULL); // Fix the delete key.
+  ::el_set(Data->EL, EL_CLIENTDATA, Data.get());
+
+  HistEvent HE;
+  ::history(Data->Hist, &HE, H_SETSIZE, 800);
+  ::history(Data->Hist, &HE, H_SETUNIQUE, 1);
+  loadHistory();
+}
+
+LineEditor::~LineEditor() {
+  saveHistory();
+
+  ::history_end(Data->Hist);
+  ::el_end(Data->EL);
+  ::fwrite("\n", 1, 1, Data->Out);
+}
+
+void LineEditor::saveHistory() {
+  if (!HistoryPath.empty()) {
+    HistEvent HE;
+    ::history(Data->Hist, &HE, H_SAVE, HistoryPath.c_str());
+  }
+}
+
+void LineEditor::loadHistory() {
+  if (!HistoryPath.empty()) {
+    HistEvent HE;
+    ::history(Data->Hist, &HE, H_LOAD, HistoryPath.c_str());
+  }
+}
+
+Optional<std::string> LineEditor::readLine() const {
+  // Call el_gets to prompt the user and read the user's input.
+  int LineLen = 0;
+  const char *Line = ::el_gets(Data->EL, &LineLen);
+
+  // Either of these may mean end-of-file.
+  if (!Line || LineLen == 0)
+    return Optional<std::string>();
+
+  // Strip any newlines off the end of the string.
+  while (LineLen > 0 &&
+         (Line[LineLen - 1] == '\n' || Line[LineLen - 1] == '\r'))
+    --LineLen;
+
+  HistEvent HE;
+  if (LineLen > 0)
+    ::history(Data->Hist, &HE, H_ENTER, Line);
+
+  return std::string(Line, LineLen);
+}
+
+#else // HAVE_LIBEDIT
+
+// Simple fgets-based implementation.
+
+struct LineEditor::InternalData {
+  FILE *In;
+  FILE *Out;
+};
+
+LineEditor::LineEditor(StringRef ProgName, StringRef HistoryPath, FILE *In,
+                       FILE *Out, FILE *Err)
+    : Prompt((ProgName + "> ").str()), Data(new InternalData) {
+  Data->In = In;
+  Data->Out = Out;
+}
+
+LineEditor::~LineEditor() {
+  ::fwrite("\n", 1, 1, Data->Out);
+}
+
+void LineEditor::saveHistory() {}
+void LineEditor::loadHistory() {}
+
+Optional<std::string> LineEditor::readLine() const {
+  ::fprintf(Data->Out, "%s", Prompt.c_str());
+
+  std::string Line;
+  do {
+    char Buf[64];
+    char *Res = ::fgets(Buf, sizeof(Buf), Data->In);
+    if (!Res) {
+      if (Line.empty())
+        return Optional<std::string>();
+      else
+        return Line;
+    }
+    Line.append(Buf);
+  } while (Line.empty() ||
+           (Line[Line.size() - 1] != '\n' && Line[Line.size() - 1] != '\r'));
+
+  while (!Line.empty() &&
+         (Line[Line.size() - 1] == '\n' || Line[Line.size() - 1] == '\r'))
+    Line.resize(Line.size() - 1);
+
+  return Line;
+}
+
+#endif // HAVE_LIBEDIT