CFGPrinter.h

Go to the documentation of this file.

//===-- CFGPrinter.h - CFG printer external interface -----------*- C++ -*-===//
//
// 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
// cfg.<fnname>.dot file for each function in the program, with a graph of the
// CFG for that function.
//
// This file defines external functions that can be called to explicitly
// instantiate the CFG printer.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_CFGPRINTER_H
#define LLVM_ANALYSIS_CFGPRINTER_H

#include "llvm/IR/CFG.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Support/GraphWriter.h"

namespace llvm {
class CFGViewerPass
    : public PassInfoMixin<CFGViewerPass> {
public:
  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};

class CFGOnlyViewerPass
    : public PassInfoMixin<CFGOnlyViewerPass> {
public:
  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};

class CFGPrinterPass
    : public PassInfoMixin<CFGPrinterPass> {
public:
  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};

class CFGOnlyPrinterPass
    : public PassInfoMixin<CFGOnlyPrinterPass> {
public:
  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};

template<>
struct DOTGraphTraits<const Function*> : public DefaultDOTGraphTraits {

  DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}

  static std::string getGraphName(const Function *F) {
    return "CFG for '" + F->getName().str() + "' function";
  }

  static std::string getSimpleNodeLabel(const BasicBlock *Node,
                                        const Function *) {
    if (!Node->getName().empty())
      return Node->getName().str();

    std::string Str;
    raw_string_ostream OS(Str);

    Node->printAsOperand(OS, false);
    return OS.str();
  }

  static std::string getCompleteNodeLabel(const BasicBlock *Node,
                                          const Function *) {
    enum { MaxColumns = 80 };
    std::string Str;
    raw_string_ostream OS(Str);

    if (Node->getName().empty()) {
      Node->printAsOperand(OS, false);
      OS << ":";
    }

    OS << *Node;
    std::string OutStr = OS.str();
    if (OutStr[0] == '\n') OutStr.erase(OutStr.begin());

    // Process string output to make it nicer...
    unsigned ColNum = 0;
    unsigned LastSpace = 0;
    for (unsigned i = 0; i != OutStr.length(); ++i) {
      if (OutStr[i] == '\n') {                            // Left justify
        OutStr[i] = '\\';
        OutStr.insert(OutStr.begin()+i+1, 'l');
        ColNum = 0;
        LastSpace = 0;
      } else if (OutStr[i] == ';') {                      // Delete comments!
        unsigned Idx = OutStr.find('\n', i+1);            // Find end of line
        OutStr.erase(OutStr.begin()+i, OutStr.begin()+Idx);
        --i;
      } else if (ColNum == MaxColumns) {                  // Wrap lines.
        // Wrap very long names even though we can't find a space.
        if (!LastSpace)
          LastSpace = i;
        OutStr.insert(LastSpace, "\\l...");
        ColNum = i - LastSpace;
        LastSpace = 0;
        i += 3; // The loop will advance 'i' again.
      }
      else
        ++ColNum;
      if (OutStr[i] == ' ')
        LastSpace = i;
    }
    return OutStr;
  }

  std::string getNodeLabel(const BasicBlock *Node,
                           const Function *Graph) {
    if (isSimple())
      return getSimpleNodeLabel(Node, Graph);
    else
      return getCompleteNodeLabel(Node, Graph);
  }

  static std::string getEdgeSourceLabel(const BasicBlock *Node,
                                        succ_const_iterator I) {
    // Label source of conditional branches with "T" or "F"
    if (const BranchInst *BI = dyn_cast<BranchInst>(Node->getTerminator()))
      if (BI->isConditional())
        return (I == succ_begin(Node)) ? "T" : "F";

    // Label source of switch edges with the associated value.
    if (const SwitchInst *SI = dyn_cast<SwitchInst>(Node->getTerminator())) {
      unsigned SuccNo = I.getSuccessorIndex();

      if (SuccNo == 0) return "def";

      std::string Str;
      raw_string_ostream OS(Str);
      auto Case = *SwitchInst::ConstCaseIt::fromSuccessorIndex(SI, SuccNo);
      OS << Case.getCaseValue()->getValue();
      return OS.str();
    }
    return "";
  }

  /// Display the raw branch weights from PGO.
  std::string getEdgeAttributes(const BasicBlock *Node, succ_const_iterator I,
                                const Function *F) {
    const Instruction *TI = Node->getTerminator();
    if (TI->getNumSuccessors() == 1)
      return "";

    MDNode *WeightsNode = TI->getMetadata(LLVMContext::MD_prof);
    if (!WeightsNode)
      return "";

    MDString *MDName = cast<MDString>(WeightsNode->getOperand(0));
    if (MDName->getString() != "branch_weights")
      return "";

    unsigned OpNo = I.getSuccessorIndex() + 1;
    if (OpNo >= WeightsNode->getNumOperands())
      return "";
    ConstantInt *Weight =
        mdconst::dyn_extract<ConstantInt>(WeightsNode->getOperand(OpNo));
    if (!Weight)
      return "";

    // Prepend a 'W' to indicate that this is a weight rather than the actual
    // profile count (due to scaling).
    return ("label=\"W:" + Twine(Weight->getZExtValue()) + "\"").str();
  }
};
} // End llvm namespace

namespace llvm {
  class FunctionPass;
  FunctionPass *createCFGPrinterLegacyPassPass ();
  FunctionPass *createCFGOnlyPrinterLegacyPassPass ();
} // End llvm namespace

#endif