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diff --git a/llvm/lib/Analysis/CFGPrinter.cpp b/llvm/lib/Analysis/CFGPrinter.cpp
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+++ b/llvm/lib/Analysis/CFGPrinter.cpp
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+//===- CFGPrinter.cpp - DOT printer for the control flow graph ------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a `-dot-cfg` analysis pass, which emits the
+// `<prefix>.<fnname>.dot` file for each function in the program, with a graph
+// of the CFG for that function. The default value for `<prefix>` is `cfg` but
+// can be customized as needed.
+//
+// The other main feature of this file is that it implements the
+// Function::viewCFG method, which is useful for debugging passes which operate
+// on the CFG.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CFGPrinter.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/FileSystem.h"
+using namespace llvm;
+
+static cl::opt<std::string> CFGFuncName(
+    "cfg-func-name", cl::Hidden,
+    cl::desc("The name of a function (or its substring)"
+             " whose CFG is viewed/printed."));
+
+static cl::opt<std::string> CFGDotFilenamePrefix(
+    "cfg-dot-filename-prefix", cl::Hidden,
+    cl::desc("The prefix used for the CFG dot file names."));
+
+namespace {
+  struct CFGViewerLegacyPass : public FunctionPass {
+    static char ID; // Pass identifcation, replacement for typeid
+    CFGViewerLegacyPass() : FunctionPass(ID) {
+      initializeCFGViewerLegacyPassPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnFunction(Function &F) override {
+      F.viewCFG();
+      return false;
+    }
+
+    void print(raw_ostream &OS, const Module* = nullptr) const override {}
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.setPreservesAll();
+    }
+  };
+}
+
+char CFGViewerLegacyPass::ID = 0;
+INITIALIZE_PASS(CFGViewerLegacyPass, "view-cfg", "View CFG of function", false, true)
+
+PreservedAnalyses CFGViewerPass::run(Function &F,
+                                     FunctionAnalysisManager &AM) {
+  F.viewCFG();
+  return PreservedAnalyses::all();
+}
+
+
+namespace {
+  struct CFGOnlyViewerLegacyPass : public FunctionPass {
+    static char ID; // Pass identifcation, replacement for typeid
+    CFGOnlyViewerLegacyPass() : FunctionPass(ID) {
+      initializeCFGOnlyViewerLegacyPassPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnFunction(Function &F) override {
+      F.viewCFGOnly();
+      return false;
+    }
+
+    void print(raw_ostream &OS, const Module* = nullptr) const override {}
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.setPreservesAll();
+    }
+  };
+}
+
+char CFGOnlyViewerLegacyPass::ID = 0;
+INITIALIZE_PASS(CFGOnlyViewerLegacyPass, "view-cfg-only",
+                "View CFG of function (with no function bodies)", false, true)
+
+PreservedAnalyses CFGOnlyViewerPass::run(Function &F,
+                                         FunctionAnalysisManager &AM) {
+  F.viewCFGOnly();
+  return PreservedAnalyses::all();
+}
+
+static void writeCFGToDotFile(Function &F, bool CFGOnly = false) {
+  if (!CFGFuncName.empty() && !F.getName().contains(CFGFuncName))
+     return;
+  std::string Filename =
+      (CFGDotFilenamePrefix + "." + F.getName() + ".dot").str();
+  errs() << "Writing '" << Filename << "'...";
+
+  std::error_code EC;
+  raw_fd_ostream File(Filename, EC, sys::fs::OF_Text);
+
+  if (!EC)
+    WriteGraph(File, (const Function*)&F, CFGOnly);
+  else
+    errs() << "  error opening file for writing!";
+  errs() << "\n";
+}
+
+namespace {
+  struct CFGPrinterLegacyPass : public FunctionPass {
+    static char ID; // Pass identification, replacement for typeid
+    CFGPrinterLegacyPass() : FunctionPass(ID) {
+      initializeCFGPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnFunction(Function &F) override {
+      writeCFGToDotFile(F);
+      return false;
+    }
+
+    void print(raw_ostream &OS, const Module* = nullptr) const override {}
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.setPreservesAll();
+    }
+  };
+}
+
+char CFGPrinterLegacyPass::ID = 0;
+INITIALIZE_PASS(CFGPrinterLegacyPass, "dot-cfg", "Print CFG of function to 'dot' file",
+                false, true)
+
+PreservedAnalyses CFGPrinterPass::run(Function &F,
+                                      FunctionAnalysisManager &AM) {
+  writeCFGToDotFile(F);
+  return PreservedAnalyses::all();
+}
+
+namespace {
+  struct CFGOnlyPrinterLegacyPass : public FunctionPass {
+    static char ID; // Pass identification, replacement for typeid
+    CFGOnlyPrinterLegacyPass() : FunctionPass(ID) {
+      initializeCFGOnlyPrinterLegacyPassPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnFunction(Function &F) override {
+      writeCFGToDotFile(F, /*CFGOnly=*/true);
+      return false;
+    }
+    void print(raw_ostream &OS, const Module* = nullptr) const override {}
+
+    void getAnalysisUsage(AnalysisUsage &AU) const override {
+      AU.setPreservesAll();
+    }
+  };
+}
+
+char CFGOnlyPrinterLegacyPass::ID = 0;
+INITIALIZE_PASS(CFGOnlyPrinterLegacyPass, "dot-cfg-only",
+   "Print CFG of function to 'dot' file (with no function bodies)",
+   false, true)
+
+PreservedAnalyses CFGOnlyPrinterPass::run(Function &F,
+                                          FunctionAnalysisManager &AM) {
+  writeCFGToDotFile(F, /*CFGOnly=*/true);
+  return PreservedAnalyses::all();
+}
+
+/// viewCFG - This function is meant for use from the debugger.  You can just
+/// say 'call F->viewCFG()' and a ghostview window should pop up from the
+/// program, displaying the CFG of the current function.  This depends on there
+/// being a 'dot' and 'gv' program in your path.
+///
+void Function::viewCFG() const {
+  if (!CFGFuncName.empty() && !getName().contains(CFGFuncName))
+     return;
+  ViewGraph(this, "cfg" + getName());
+}
+
+/// viewCFGOnly - This function is meant for use from the debugger.  It works
+/// just like viewCFG, but it does not include the contents of basic blocks
+/// into the nodes, just the label.  If you are only interested in the CFG
+/// this can make the graph smaller.
+///
+void Function::viewCFGOnly() const {
+  if (!CFGFuncName.empty() && !getName().contains(CFGFuncName))
+     return;
+  ViewGraph(this, "cfg" + getName(), true);
+}
+
+FunctionPass *llvm::createCFGPrinterLegacyPassPass () {
+  return new CFGPrinterLegacyPass();
+}
+
+FunctionPass *llvm::createCFGOnlyPrinterLegacyPassPass () {
+  return new CFGOnlyPrinterLegacyPass();
+}
+