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"
27 /// \brief This class emits a version of the loop where run-time checks ensure
28 /// that may-alias pointers can't overlap.
30 /// It currently only supports single-exit loops and assumes that the loop
31 /// already has a preheader.
32 class LoopVersioning {
34 LoopVersioning(SmallVector<RuntimePointerChecking::PointerCheck, 4> Checks,
35 const LoopAccessInfo &LAI, Loop *L, LoopInfo *LI,
38 /// \brief Performs the CFG manipulation part of versioning the loop including
39 /// the DominatorTree and LoopInfo updates.
41 /// The loop that was used to construct the class will be the "versioned" loop
42 /// i.e. the loop that will receive control if all the memchecks pass.
44 /// This allows the loop transform pass to operate on the same loop regardless
45 /// of whether versioning was necessary or not:
49 /// if versioning is necessary version L
51 void versionLoop(Pass *P);
53 /// \brief Adds the necessary PHI nodes for the versioned loops based on the
54 /// loop-defined values used outside of the loop.
56 /// This needs to be called after versionLoop if there are defs in the loop
57 /// that are used outside the loop. FIXME: this should be invoked internally
58 /// by versionLoop and made private.
59 void addPHINodes(const SmallVectorImpl<Instruction *> &DefsUsedOutside);
61 /// \brief Returns the versioned loop. Control flows here if pointers in the
62 /// loop don't alias (i.e. all memchecks passed). (This loop is actually the
63 /// same as the original loop that we got constructed with.)
64 Loop *getVersionedLoop() { return VersionedLoop; }
66 /// \brief Returns the fall-back loop. Control flows here if pointers in the
67 /// loop may alias (i.e. one of the memchecks failed).
68 Loop *getNonVersionedLoop() { return NonVersionedLoop; }
71 /// \brief The original loop. This becomes the "versioned" one. I.e.,
72 /// control flows here if pointers in the loop don't alias.
74 /// \brief The fall-back loop. I.e. control flows here if pointers in the
75 /// loop may alias (memchecks failed).
76 Loop *NonVersionedLoop;
78 /// \brief This maps the instructions from VersionedLoop to their counterpart
79 /// in NonVersionedLoop.
80 ValueToValueMapTy VMap;
82 /// \brief The set of checks that we are versioning for.
83 SmallVector<RuntimePointerChecking::PointerCheck, 4> Checks;
85 /// \brief Analyses used.
86 const LoopAccessInfo &LAI;