1 //===- LoopVersioning.h - Utility to version a loop -------------*- 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 a utility class to perform loop versioning. The versioned
11 // loop speculates that otherwise may-aliasing memory accesses don't overlap and
12 // emits checks to prove this.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_TRANSFORMS_UTILS_LOOPVERSIONING_H
17 #define LLVM_TRANSFORMS_UTILS_LOOPVERSIONING_H
19 #include "llvm/Transforms/Utils/ValueMapper.h"
20 #include "llvm/Transforms/Utils/LoopUtils.h"
28 /// \brief This class emits a version of the loop where run-time checks ensure
29 /// that may-alias pointers can't overlap.
31 /// It currently only supports single-exit loops and assumes that the loop
32 /// already has a preheader.
33 class LoopVersioning {
35 /// \brief Expects MemCheck, LoopAccessInfo, Loop, LoopInfo, DominatorTree
36 /// as input. It uses runtime check provided by user.
37 LoopVersioning(SmallVector<RuntimePointerChecking::PointerCheck, 4> Checks,
38 const LoopAccessInfo &LAI, Loop *L, LoopInfo *LI,
41 /// \brief Expects LoopAccessInfo, Loop, LoopInfo, DominatorTree as input.
42 /// It uses default runtime check provided by LoopAccessInfo.
43 LoopVersioning(const LoopAccessInfo &LAInfo, Loop *L, LoopInfo *LI,
46 /// \brief Performs the CFG manipulation part of versioning the loop including
47 /// the DominatorTree and LoopInfo updates.
49 /// The loop that was used to construct the class will be the "versioned" loop
50 /// i.e. the loop that will receive control if all the memchecks pass.
52 /// This allows the loop transform pass to operate on the same loop regardless
53 /// of whether versioning was necessary or not:
57 /// if versioning is necessary version L
59 void versionLoop() { versionLoop(findDefsUsedOutsideOfLoop(VersionedLoop)); }
61 /// \brief Same but if the client has already precomputed the set of values
62 /// used outside the loop, this API will allows passing that.
63 void versionLoop(const SmallVectorImpl<Instruction *> &DefsUsedOutside);
65 /// \brief Returns the versioned loop. Control flows here if pointers in the
66 /// loop don't alias (i.e. all memchecks passed). (This loop is actually the
67 /// same as the original loop that we got constructed with.)
68 Loop *getVersionedLoop() { return VersionedLoop; }
70 /// \brief Returns the fall-back loop. Control flows here if pointers in the
71 /// loop may alias (i.e. one of the memchecks failed).
72 Loop *getNonVersionedLoop() { return NonVersionedLoop; }
75 /// \brief Adds the necessary PHI nodes for the versioned loops based on the
76 /// loop-defined values used outside of the loop.
78 /// This needs to be called after versionLoop if there are defs in the loop
79 /// that are used outside the loop.
80 void addPHINodes(const SmallVectorImpl<Instruction *> &DefsUsedOutside);
82 /// \brief The original loop. This becomes the "versioned" one. I.e.,
83 /// control flows here if pointers in the loop don't alias.
85 /// \brief The fall-back loop. I.e. control flows here if pointers in the
86 /// loop may alias (memchecks failed).
87 Loop *NonVersionedLoop;
89 /// \brief This maps the instructions from VersionedLoop to their counterpart
90 /// in NonVersionedLoop.
91 ValueToValueMapTy VMap;
93 /// \brief The set of checks that we are versioning for.
94 SmallVector<RuntimePointerChecking::PointerCheck, 4> Checks;
96 /// \brief Analyses used.
97 const LoopAccessInfo &LAI;