Andrew Scull | 5e1ddfa | 2018-08-14 10:06:54 +0100 | [diff] [blame] | 1 | //===- llvm/CodeGen/MachineLoopInfo.h - Natural Loop Calculator -*- 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 | // This file defines the MachineLoopInfo class that is used to identify natural |
| 11 | // loops and determine the loop depth of various nodes of the CFG. Note that |
| 12 | // natural loops may actually be several loops that share the same header node. |
| 13 | // |
| 14 | // This analysis calculates the nesting structure of loops in a function. For |
| 15 | // each natural loop identified, this analysis identifies natural loops |
| 16 | // contained entirely within the loop and the basic blocks the make up the loop. |
| 17 | // |
| 18 | // It can calculate on the fly various bits of information, for example: |
| 19 | // |
| 20 | // * whether there is a preheader for the loop |
| 21 | // * the number of back edges to the header |
| 22 | // * whether or not a particular block branches out of the loop |
| 23 | // * the successor blocks of the loop |
| 24 | // * the loop depth |
| 25 | // * the trip count |
| 26 | // * etc... |
| 27 | // |
| 28 | //===----------------------------------------------------------------------===// |
| 29 | |
| 30 | #ifndef LLVM_CODEGEN_MACHINELOOPINFO_H |
| 31 | #define LLVM_CODEGEN_MACHINELOOPINFO_H |
| 32 | |
| 33 | #include "llvm/Analysis/LoopInfo.h" |
| 34 | #include "llvm/CodeGen/MachineBasicBlock.h" |
| 35 | #include "llvm/CodeGen/MachineFunctionPass.h" |
| 36 | #include "llvm/IR/DebugLoc.h" |
| 37 | #include "llvm/Pass.h" |
| 38 | |
| 39 | namespace llvm { |
| 40 | |
| 41 | // Implementation in LoopInfoImpl.h |
| 42 | class MachineLoop; |
| 43 | extern template class LoopBase<MachineBasicBlock, MachineLoop>; |
| 44 | |
| 45 | class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> { |
| 46 | public: |
| 47 | /// Return the "top" block in the loop, which is the first block in the linear |
| 48 | /// layout, ignoring any parts of the loop not contiguous with the part that |
| 49 | /// contains the header. |
| 50 | MachineBasicBlock *getTopBlock(); |
| 51 | |
| 52 | /// Return the "bottom" block in the loop, which is the last block in the |
| 53 | /// linear layout, ignoring any parts of the loop not contiguous with the part |
| 54 | /// that contains the header. |
| 55 | MachineBasicBlock *getBottomBlock(); |
| 56 | |
Andrew Scull | cdfcccc | 2018-10-05 20:58:37 +0100 | [diff] [blame^] | 57 | /// Find the block that contains the loop control variable and the |
Andrew Scull | 5e1ddfa | 2018-08-14 10:06:54 +0100 | [diff] [blame] | 58 | /// loop test. This will return the latch block if it's one of the exiting |
| 59 | /// blocks. Otherwise, return the exiting block. Return 'null' when |
| 60 | /// multiple exiting blocks are present. |
| 61 | MachineBasicBlock *findLoopControlBlock(); |
| 62 | |
| 63 | /// Return the debug location of the start of this loop. |
| 64 | /// This looks for a BB terminating instruction with a known debug |
| 65 | /// location by looking at the preheader and header blocks. If it |
| 66 | /// cannot find a terminating instruction with location information, |
| 67 | /// it returns an unknown location. |
| 68 | DebugLoc getStartLoc() const; |
| 69 | |
| 70 | void dump() const; |
| 71 | |
| 72 | private: |
| 73 | friend class LoopInfoBase<MachineBasicBlock, MachineLoop>; |
| 74 | |
| 75 | explicit MachineLoop(MachineBasicBlock *MBB) |
| 76 | : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {} |
| 77 | |
| 78 | MachineLoop() = default; |
| 79 | }; |
| 80 | |
| 81 | // Implementation in LoopInfoImpl.h |
| 82 | extern template class LoopInfoBase<MachineBasicBlock, MachineLoop>; |
| 83 | |
| 84 | class MachineLoopInfo : public MachineFunctionPass { |
| 85 | friend class LoopBase<MachineBasicBlock, MachineLoop>; |
| 86 | |
| 87 | LoopInfoBase<MachineBasicBlock, MachineLoop> LI; |
| 88 | |
| 89 | public: |
| 90 | static char ID; // Pass identification, replacement for typeid |
| 91 | |
| 92 | MachineLoopInfo() : MachineFunctionPass(ID) { |
| 93 | initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry()); |
| 94 | } |
| 95 | MachineLoopInfo(const MachineLoopInfo &) = delete; |
| 96 | MachineLoopInfo &operator=(const MachineLoopInfo &) = delete; |
| 97 | |
| 98 | LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; } |
| 99 | |
Andrew Scull | cdfcccc | 2018-10-05 20:58:37 +0100 | [diff] [blame^] | 100 | /// Find the block that either is the loop preheader, or could |
Andrew Scull | 5e1ddfa | 2018-08-14 10:06:54 +0100 | [diff] [blame] | 101 | /// speculatively be used as the preheader. This is e.g. useful to place |
| 102 | /// loop setup code. Code that cannot be speculated should not be placed |
| 103 | /// here. SpeculativePreheader is controlling whether it also tries to |
| 104 | /// find the speculative preheader if the regular preheader is not present. |
| 105 | MachineBasicBlock *findLoopPreheader(MachineLoop *L, |
| 106 | bool SpeculativePreheader = false) const; |
| 107 | |
| 108 | /// The iterator interface to the top-level loops in the current function. |
| 109 | using iterator = LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator; |
| 110 | inline iterator begin() const { return LI.begin(); } |
| 111 | inline iterator end() const { return LI.end(); } |
| 112 | bool empty() const { return LI.empty(); } |
| 113 | |
| 114 | /// Return the innermost loop that BB lives in. If a basic block is in no loop |
| 115 | /// (for example the entry node), null is returned. |
| 116 | inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const { |
| 117 | return LI.getLoopFor(BB); |
| 118 | } |
| 119 | |
| 120 | /// Same as getLoopFor. |
| 121 | inline const MachineLoop *operator[](const MachineBasicBlock *BB) const { |
| 122 | return LI.getLoopFor(BB); |
| 123 | } |
| 124 | |
| 125 | /// Return the loop nesting level of the specified block. |
| 126 | inline unsigned getLoopDepth(const MachineBasicBlock *BB) const { |
| 127 | return LI.getLoopDepth(BB); |
| 128 | } |
| 129 | |
| 130 | /// True if the block is a loop header node. |
| 131 | inline bool isLoopHeader(const MachineBasicBlock *BB) const { |
| 132 | return LI.isLoopHeader(BB); |
| 133 | } |
| 134 | |
| 135 | /// Calculate the natural loop information. |
| 136 | bool runOnMachineFunction(MachineFunction &F) override; |
| 137 | |
| 138 | void releaseMemory() override { LI.releaseMemory(); } |
| 139 | |
| 140 | void getAnalysisUsage(AnalysisUsage &AU) const override; |
| 141 | |
| 142 | /// This removes the specified top-level loop from this loop info object. The |
| 143 | /// loop is not deleted, as it will presumably be inserted into another loop. |
| 144 | inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); } |
| 145 | |
| 146 | /// Change the top-level loop that contains BB to the specified loop. This |
| 147 | /// should be used by transformations that restructure the loop hierarchy |
| 148 | /// tree. |
| 149 | inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) { |
| 150 | LI.changeLoopFor(BB, L); |
| 151 | } |
| 152 | |
| 153 | /// Replace the specified loop in the top-level loops list with the indicated |
| 154 | /// loop. |
| 155 | inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) { |
| 156 | LI.changeTopLevelLoop(OldLoop, NewLoop); |
| 157 | } |
| 158 | |
| 159 | /// This adds the specified loop to the collection of top-level loops. |
| 160 | inline void addTopLevelLoop(MachineLoop *New) { |
| 161 | LI.addTopLevelLoop(New); |
| 162 | } |
| 163 | |
| 164 | /// This method completely removes BB from all data structures, including all |
| 165 | /// of the Loop objects it is nested in and our mapping from |
| 166 | /// MachineBasicBlocks to loops. |
| 167 | void removeBlock(MachineBasicBlock *BB) { |
| 168 | LI.removeBlock(BB); |
| 169 | } |
| 170 | }; |
| 171 | |
| 172 | // Allow clients to walk the list of nested loops... |
| 173 | template <> struct GraphTraits<const MachineLoop*> { |
| 174 | using NodeRef = const MachineLoop *; |
| 175 | using ChildIteratorType = MachineLoopInfo::iterator; |
| 176 | |
| 177 | static NodeRef getEntryNode(const MachineLoop *L) { return L; } |
| 178 | static ChildIteratorType child_begin(NodeRef N) { return N->begin(); } |
| 179 | static ChildIteratorType child_end(NodeRef N) { return N->end(); } |
| 180 | }; |
| 181 | |
| 182 | template <> struct GraphTraits<MachineLoop*> { |
| 183 | using NodeRef = MachineLoop *; |
| 184 | using ChildIteratorType = MachineLoopInfo::iterator; |
| 185 | |
| 186 | static NodeRef getEntryNode(MachineLoop *L) { return L; } |
| 187 | static ChildIteratorType child_begin(NodeRef N) { return N->begin(); } |
| 188 | static ChildIteratorType child_end(NodeRef N) { return N->end(); } |
| 189 | }; |
| 190 | |
| 191 | } // end namespace llvm |
| 192 | |
| 193 | #endif // LLVM_CODEGEN_MACHINELOOPINFO_H |