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95 lines
4.0 KiB
C++
95 lines
4.0 KiB
C++
//===-- Analysis/CFG.h - BasicBlock Analyses --------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This family of functions performs analyses on basic blocks, and instructions
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// contained within basic blocks.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_CFG_H
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#define LLVM_ANALYSIS_CFG_H
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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namespace llvm {
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class BasicBlock;
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class DominatorTree;
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class Function;
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class Instruction;
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class LoopInfo;
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class TerminatorInst;
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/// Analyze the specified function to find all of the loop backedges in the
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/// function and return them. This is a relatively cheap (compared to
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/// computing dominators and loop info) analysis.
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///
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/// The output is added to Result, as pairs of <from,to> edge info.
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void FindFunctionBackedges(
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const Function &F,
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SmallVectorImpl<std::pair<const BasicBlock *, const BasicBlock *> > &
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Result);
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/// Search for the specified successor of basic block BB and return its position
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/// in the terminator instruction's list of successors. It is an error to call
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/// this with a block that is not a successor.
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unsigned GetSuccessorNumber(const BasicBlock *BB, const BasicBlock *Succ);
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/// Return true if the specified edge is a critical edge. Critical edges are
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/// edges from a block with multiple successors to a block with multiple
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/// predecessors.
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///
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bool isCriticalEdge(const TerminatorInst *TI, unsigned SuccNum,
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bool AllowIdenticalEdges = false);
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/// \brief Determine whether instruction 'To' is reachable from 'From',
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/// returning true if uncertain.
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///
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/// Determine whether there is a path from From to To within a single function.
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/// Returns false only if we can prove that once 'From' has been executed then
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/// 'To' can not be executed. Conservatively returns true.
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///
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/// This function is linear with respect to the number of blocks in the CFG,
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/// walking down successors from From to reach To, with a fixed threshold.
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/// Using DT or LI allows us to answer more quickly. LI reduces the cost of
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/// an entire loop of any number of blocsk to be the same as the cost of a
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/// single block. DT reduces the cost by allowing the search to terminate when
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/// we find a block that dominates the block containing 'To'. DT is most useful
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/// on branchy code but not loops, and LI is most useful on code with loops but
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/// does not help on branchy code outside loops.
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bool isPotentiallyReachable(const Instruction *From, const Instruction *To,
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const DominatorTree *DT = nullptr,
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const LoopInfo *LI = nullptr);
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/// \brief Determine whether block 'To' is reachable from 'From', returning
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/// true if uncertain.
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///
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/// Determine whether there is a path from From to To within a single function.
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/// Returns false only if we can prove that once 'From' has been reached then
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/// 'To' can not be executed. Conservatively returns true.
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bool isPotentiallyReachable(const BasicBlock *From, const BasicBlock *To,
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const DominatorTree *DT = nullptr,
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const LoopInfo *LI = nullptr);
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/// \brief Determine whether there is at least one path from a block in
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/// 'Worklist' to 'StopBB', returning true if uncertain.
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///
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/// Determine whether there is a path from at least one block in Worklist to
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/// StopBB within a single function. Returns false only if we can prove that
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/// once any block in 'Worklist' has been reached then 'StopBB' can not be
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/// executed. Conservatively returns true.
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bool isPotentiallyReachableFromMany(SmallVectorImpl<BasicBlock *> &Worklist,
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BasicBlock *StopBB,
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const DominatorTree *DT = nullptr,
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const LoopInfo *LI = nullptr);
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} // End llvm namespace
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#endif
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