LCOV - code coverage report
Current view: top level - include/llvm/Analysis - IteratedDominanceFrontier.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 5 13 38.5 %
Date: 2017-09-14 15:23:50 Functions: 0 8 0.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- IteratedDominanceFrontier.h - Calculate IDF --------------*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : /// \brief Compute iterated dominance frontiers using a linear time algorithm.
      11             : ///
      12             : /// The algorithm used here is based on:
      13             : ///
      14             : ///   Sreedhar and Gao. A linear time algorithm for placing phi-nodes.
      15             : ///   In Proceedings of the 22nd ACM SIGPLAN-SIGACT Symposium on Principles of
      16             : ///   Programming Languages
      17             : ///   POPL '95. ACM, New York, NY, 62-73.
      18             : ///
      19             : /// It has been modified to not explicitly use the DJ graph data structure and
      20             : /// to directly compute pruned SSA using per-variable liveness information.
      21             : //
      22             : //===----------------------------------------------------------------------===//
      23             : 
      24             : #ifndef LLVM_ANALYSIS_IDF_H
      25             : #define LLVM_ANALYSIS_IDF_H
      26             : 
      27             : #include "llvm/ADT/DenseMap.h"
      28             : #include "llvm/ADT/SmallPtrSet.h"
      29             : #include "llvm/ADT/SmallVector.h"
      30             : #include "llvm/IR/BasicBlock.h"
      31             : #include "llvm/IR/Dominators.h"
      32             : 
      33             : namespace llvm {
      34             : 
      35             : /// \brief Determine the iterated dominance frontier, given a set of defining
      36             : /// blocks, and optionally, a set of live-in blocks.
      37             : ///
      38             : /// In turn, the results can be used to place phi nodes.
      39             : ///
      40             : /// This algorithm is a linear time computation of Iterated Dominance Frontiers,
      41             : /// pruned using the live-in set.
      42             : /// By default, liveness is not used to prune the IDF computation.
      43             : /// The template parameters should be either BasicBlock* or Inverse<BasicBlock
      44             : /// *>, depending on if you want the forward or reverse IDF.
      45             : template <class NodeTy, bool IsPostDom>
      46             : class IDFCalculator {
      47             :  public:
      48       79225 :   IDFCalculator(DominatorTreeBase<BasicBlock, IsPostDom> &DT)
      49       79225 :       : DT(DT), useLiveIn(false) {}
      50             : 
      51             :   /// \brief Give the IDF calculator the set of blocks in which the value is
      52             :   /// defined.  This is equivalent to the set of starting blocks it should be
      53             :   /// calculating the IDF for (though later gets pruned based on liveness).
      54             :   ///
      55             :   /// Note: This set *must* live for the entire lifetime of the IDF calculator.
      56           0 :   void setDefiningBlocks(const SmallPtrSetImpl<BasicBlock *> &Blocks) {
      57       47540 :     DefBlocks = &Blocks;
      58           0 :   }
      59             : 
      60             :   /// \brief Give the IDF calculator the set of blocks in which the value is
      61             :   /// live on entry to the block.   This is used to prune the IDF calculation to
      62             :   /// not include blocks where any phi insertion would be dead.
      63             :   ///
      64             :   /// Note: This set *must* live for the entire lifetime of the IDF calculator.
      65             : 
      66           0 :   void setLiveInBlocks(const SmallPtrSetImpl<BasicBlock *> &Blocks) {
      67       13109 :     LiveInBlocks = &Blocks;
      68       13109 :     useLiveIn = true;
      69           0 :   }
      70             : 
      71             :   /// \brief Reset the live-in block set to be empty, and tell the IDF
      72             :   /// calculator to not use liveness anymore.
      73           0 :   void resetLiveInBlocks() {
      74           0 :     LiveInBlocks = nullptr;
      75           0 :     useLiveIn = false;
      76           0 :   }
      77             : 
      78             :   /// \brief Calculate iterated dominance frontiers
      79             :   ///
      80             :   /// This uses the linear-time phi algorithm based on DJ-graphs mentioned in
      81             :   /// the file-level comment.  It performs DF->IDF pruning using the live-in
      82             :   /// set, to avoid computing the IDF for blocks where an inserted PHI node
      83             :   /// would be dead.
      84             :   void calculate(SmallVectorImpl<BasicBlock *> &IDFBlocks);
      85             : 
      86             : private:
      87             :  DominatorTreeBase<BasicBlock, IsPostDom> &DT;
      88             :  bool useLiveIn;
      89             :  const SmallPtrSetImpl<BasicBlock *> *LiveInBlocks;
      90             :  const SmallPtrSetImpl<BasicBlock *> *DefBlocks;
      91             : };
      92             : typedef IDFCalculator<BasicBlock *, false> ForwardIDFCalculator;
      93             : typedef IDFCalculator<Inverse<BasicBlock *>, true> ReverseIDFCalculator;
      94             : }
      95             : #endif

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