1 //===- llvm/Analysis/OrderedBasicBlock.h --------------------- -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the OrderedBasicBlock class. OrderedBasicBlock maintains
11 // an interface where clients can query if one instruction comes before another
12 // in a BasicBlock. Since BasicBlock currently lacks a reliable way to query
13 // relative position between instructions one can use OrderedBasicBlock to do
14 // such queries. OrderedBasicBlock is lazily built on a source BasicBlock and
15 // maintains an internal Instruction -> Position map. A OrderedBasicBlock
16 // instance should be discarded whenever the source BasicBlock changes.
18 // It's currently used by the CaptureTracker in order to find relative
19 // positions of a pair of instructions inside a BasicBlock.
21 //===----------------------------------------------------------------------===//
23 #ifndef LLVM_ANALYSIS_ORDEREDBASICBLOCK_H
24 #define LLVM_ANALYSIS_ORDEREDBASICBLOCK_H
26 #include "llvm/ADT/DenseMap.h"
27 #include "llvm/IR/BasicBlock.h"
34 class OrderedBasicBlock {
36 /// \brief Map a instruction to its position in a BasicBlock.
37 SmallDenseMap<const Instruction *, unsigned, 32> NumberedInsts;
39 /// \brief Keep track of last instruction inserted into \p NumberedInsts.
40 /// It speeds up queries for uncached instructions by providing a start point
41 /// for new queries in OrderedBasicBlock::comesBefore.
42 BasicBlock::const_iterator LastInstFound;
44 /// \brief The position/number to tag the next instruction to be found.
47 /// \brief The source BasicBlock to map.
50 /// \brief Given no cached results, find if \p A comes before \p B in \p BB.
51 /// Cache and number out instruction while walking \p BB.
52 bool comesBefore(const Instruction *A, const Instruction *B);
55 OrderedBasicBlock(const BasicBlock *BasicB);
57 /// \brief Find out whether \p A dominates \p B, meaning whether \p A
58 /// comes before \p B in \p BB. This is a simplification that considers
59 /// cached instruction positions and ignores other basic blocks, being
60 /// only relevant to compare relative instructions positions inside \p BB.
61 bool dominates(const Instruction *A, const Instruction *B);
64 } // End llvm namespace