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/Analysis/LoopAccessAnalysis.h"
20 #include "llvm/Transforms/Utils/ValueMapper.h"
21 #include "llvm/Transforms/Utils/LoopUtils.h"
29 /// \brief This class emits a version of the loop where run-time checks ensure
30 /// that may-alias pointers can't overlap.
32 /// It currently only supports single-exit loops and assumes that the loop
33 /// already has a preheader.
34 class LoopVersioning {
36 /// \brief Expects MemCheck, LoopAccessInfo, Loop, LoopInfo, DominatorTree
37 /// as input. It uses runtime check provided by user.
38 LoopVersioning(SmallVector<RuntimePointerChecking::PointerCheck, 4> Checks,
39 const LoopAccessInfo &LAI, Loop *L, LoopInfo *LI,
42 /// \brief Expects LoopAccessInfo, Loop, LoopInfo, DominatorTree as input.
43 /// It uses default runtime check provided by LoopAccessInfo.
44 LoopVersioning(const LoopAccessInfo &LAInfo, Loop *L, LoopInfo *LI,
47 /// \brief Performs the CFG manipulation part of versioning the loop including
48 /// the DominatorTree and LoopInfo updates.
50 /// The loop that was used to construct the class will be the "versioned" loop
51 /// i.e. the loop that will receive control if all the memchecks pass.
53 /// This allows the loop transform pass to operate on the same loop regardless
54 /// of whether versioning was necessary or not:
58 /// if versioning is necessary version L
60 void versionLoop() { versionLoop(findDefsUsedOutsideOfLoop(VersionedLoop)); }
62 /// \brief Same but if the client has already precomputed the set of values
63 /// used outside the loop, this API will allows passing that.
64 void versionLoop(const SmallVectorImpl<Instruction *> &DefsUsedOutside);
66 /// \brief Returns the versioned loop. Control flows here if pointers in the
67 /// loop don't alias (i.e. all memchecks passed). (This loop is actually the
68 /// same as the original loop that we got constructed with.)
69 Loop *getVersionedLoop() { return VersionedLoop; }
71 /// \brief Returns the fall-back loop. Control flows here if pointers in the
72 /// loop may alias (i.e. one of the memchecks failed).
73 Loop *getNonVersionedLoop() { return NonVersionedLoop; }
76 /// \brief Adds the necessary PHI nodes for the versioned loops based on the
77 /// loop-defined values used outside of the loop.
79 /// This needs to be called after versionLoop if there are defs in the loop
80 /// that are used outside the loop.
81 void addPHINodes(const SmallVectorImpl<Instruction *> &DefsUsedOutside);
83 /// \brief The original loop. This becomes the "versioned" one. I.e.,
84 /// control flows here if pointers in the loop don't alias.
86 /// \brief The fall-back loop. I.e. control flows here if pointers in the
87 /// loop may alias (memchecks failed).
88 Loop *NonVersionedLoop;
90 /// \brief This maps the instructions from VersionedLoop to their counterpart
91 /// in NonVersionedLoop.
92 ValueToValueMapTy VMap;
94 /// \brief The set of checks that we are versioning for.
95 SmallVector<RuntimePointerChecking::PointerCheck, 4> Checks;
97 /// \brief Analyses used.
98 const LoopAccessInfo &LAI;