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thirdparty/capstone/suite/synctools/tablegen/include/llvm/CodeGen/MachineLoopInfo.h

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+//===- llvm/CodeGen/MachineLoopInfo.h - Natural Loop Calculator -*- 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 the MachineLoopInfo class that is used to identify natural
+// loops and determine the loop depth of various nodes of the CFG.  Note that
+// natural loops may actually be several loops that share the same header node.
+//
+// This analysis calculates the nesting structure of loops in a function.  For
+// each natural loop identified, this analysis identifies natural loops
+// contained entirely within the loop and the basic blocks the make up the loop.
+//
+// It can calculate on the fly various bits of information, for example:
+//
+//  * whether there is a preheader for the loop
+//  * the number of back edges to the header
+//  * whether or not a particular block branches out of the loop
+//  * the successor blocks of the loop
+//  * the loop depth
+//  * the trip count
+//  * etc...
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MACHINELOOPINFO_H
+#define LLVM_CODEGEN_MACHINELOOPINFO_H
+
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/IR/DebugLoc.h"
+#include "llvm/Pass.h"
+
+namespace llvm {
+
+class MachineDominatorTree;
+// Implementation in LoopInfoImpl.h
+class MachineLoop;
+extern template class LoopBase<MachineBasicBlock, MachineLoop>;
+
+class MachineLoop : public LoopBase<MachineBasicBlock, MachineLoop> {
+public:
+  /// Return the "top" block in the loop, which is the first block in the linear
+  /// layout, ignoring any parts of the loop not contiguous with the part that
+  /// contains the header.
+  MachineBasicBlock *getTopBlock();
+
+  /// Return the "bottom" block in the loop, which is the last block in the
+  /// linear layout, ignoring any parts of the loop not contiguous with the part
+  /// that contains the header.
+  MachineBasicBlock *getBottomBlock();
+
+  /// Find the block that contains the loop control variable and the
+  /// loop test. This will return the latch block if it's one of the exiting
+  /// blocks. Otherwise, return the exiting block. Return 'null' when
+  /// multiple exiting blocks are present.
+  MachineBasicBlock *findLoopControlBlock();
+
+  /// Return the debug location of the start of this loop.
+  /// This looks for a BB terminating instruction with a known debug
+  /// location by looking at the preheader and header blocks. If it
+  /// cannot find a terminating instruction with location information,
+  /// it returns an unknown location.
+  DebugLoc getStartLoc() const;
+
+  /// Returns true if the instruction is loop invariant.
+  /// I.e., all virtual register operands are defined outside of the loop,
+  /// physical registers aren't accessed explicitly, and there are no side
+  /// effects that aren't captured by the operands or other flags.
+  bool isLoopInvariant(MachineInstr &I) const;
+
+  void dump() const;
+
+private:
+  friend class LoopInfoBase<MachineBasicBlock, MachineLoop>;
+
+  explicit MachineLoop(MachineBasicBlock *MBB)
+    : LoopBase<MachineBasicBlock, MachineLoop>(MBB) {}
+
+  MachineLoop() = default;
+};
+
+// Implementation in LoopInfoImpl.h
+extern template class LoopInfoBase<MachineBasicBlock, MachineLoop>;
+
+class MachineLoopInfo : public MachineFunctionPass {
+  friend class LoopBase<MachineBasicBlock, MachineLoop>;
+
+  LoopInfoBase<MachineBasicBlock, MachineLoop> LI;
+
+public:
+  static char ID; // Pass identification, replacement for typeid
+
+  MachineLoopInfo();
+  explicit MachineLoopInfo(MachineDominatorTree &MDT)
+      : MachineFunctionPass(ID) {
+    calculate(MDT);
+  }
+  MachineLoopInfo(const MachineLoopInfo &) = delete;
+  MachineLoopInfo &operator=(const MachineLoopInfo &) = delete;
+
+  LoopInfoBase<MachineBasicBlock, MachineLoop>& getBase() { return LI; }
+
+  /// Find the block that either is the loop preheader, or could
+  /// speculatively be used as the preheader. This is e.g. useful to place
+  /// loop setup code. Code that cannot be speculated should not be placed
+  /// here. SpeculativePreheader is controlling whether it also tries to
+  /// find the speculative preheader if the regular preheader is not present.
+  /// With FindMultiLoopPreheader = false, nullptr will be returned if the found
+  /// preheader is the preheader of multiple loops.
+  MachineBasicBlock *
+  findLoopPreheader(MachineLoop *L, bool SpeculativePreheader = false,
+                    bool FindMultiLoopPreheader = false) const;
+
+  /// The iterator interface to the top-level loops in the current function.
+  using iterator = LoopInfoBase<MachineBasicBlock, MachineLoop>::iterator;
+  inline iterator begin() const { return LI.begin(); }
+  inline iterator end() const { return LI.end(); }
+  bool empty() const { return LI.empty(); }
+
+  /// Return the innermost loop that BB lives in. If a basic block is in no loop
+  /// (for example the entry node), null is returned.
+  inline MachineLoop *getLoopFor(const MachineBasicBlock *BB) const {
+    return LI.getLoopFor(BB);
+  }
+
+  /// Same as getLoopFor.
+  inline const MachineLoop *operator[](const MachineBasicBlock *BB) const {
+    return LI.getLoopFor(BB);
+  }
+
+  /// Return the loop nesting level of the specified block.
+  inline unsigned getLoopDepth(const MachineBasicBlock *BB) const {
+    return LI.getLoopDepth(BB);
+  }
+
+  /// True if the block is a loop header node.
+  inline bool isLoopHeader(const MachineBasicBlock *BB) const {
+    return LI.isLoopHeader(BB);
+  }
+
+  /// Calculate the natural loop information.
+  bool runOnMachineFunction(MachineFunction &F) override;
+  void calculate(MachineDominatorTree &MDT);
+
+  void releaseMemory() override { LI.releaseMemory(); }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  /// This removes the specified top-level loop from this loop info object. The
+  /// loop is not deleted, as it will presumably be inserted into another loop.
+  inline MachineLoop *removeLoop(iterator I) { return LI.removeLoop(I); }
+
+  /// Change the top-level loop that contains BB to the specified loop. This
+  /// should be used by transformations that restructure the loop hierarchy
+  /// tree.
+  inline void changeLoopFor(MachineBasicBlock *BB, MachineLoop *L) {
+    LI.changeLoopFor(BB, L);
+  }
+
+  /// Replace the specified loop in the top-level loops list with the indicated
+  /// loop.
+  inline void changeTopLevelLoop(MachineLoop *OldLoop, MachineLoop *NewLoop) {
+    LI.changeTopLevelLoop(OldLoop, NewLoop);
+  }
+
+  /// This adds the specified loop to the collection of top-level loops.
+  inline void addTopLevelLoop(MachineLoop *New) {
+    LI.addTopLevelLoop(New);
+  }
+
+  /// This method completely removes BB from all data structures, including all
+  /// of the Loop objects it is nested in and our mapping from
+  /// MachineBasicBlocks to loops.
+  void removeBlock(MachineBasicBlock *BB) {
+    LI.removeBlock(BB);
+  }
+};
+
+// Allow clients to walk the list of nested loops...
+template <> struct GraphTraits<const MachineLoop*> {
+  using NodeRef = const MachineLoop *;
+  using ChildIteratorType = MachineLoopInfo::iterator;
+
+  static NodeRef getEntryNode(const MachineLoop *L) { return L; }
+  static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
+  static ChildIteratorType child_end(NodeRef N) { return N->end(); }
+};
+
+template <> struct GraphTraits<MachineLoop*> {
+  using NodeRef = MachineLoop *;
+  using ChildIteratorType = MachineLoopInfo::iterator;
+
+  static NodeRef getEntryNode(MachineLoop *L) { return L; }
+  static ChildIteratorType child_begin(NodeRef N) { return N->begin(); }
+  static ChildIteratorType child_end(NodeRef N) { return N->end(); }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_CODEGEN_MACHINELOOPINFO_H