1//===- llvm/Analysis/ScalarEvolutionNormalization.h - See below -*- 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 utilities for working with "normalized" ScalarEvolution
11// expressions.
12//
13// The following example illustrates post-increment uses and how normalized
14// expressions help.
15//
16//   for (i=0; i!=n; ++i) {
17//     ...
18//   }
19//   use(i);
20//
21// While the expression for most uses of i inside the loop is {0,+,1}<%L>, the
22// expression for the use of i outside the loop is {1,+,1}<%L>, since i is
23// incremented at the end of the loop body. This is inconveient, since it
24// suggests that we need two different induction variables, one that starts
25// at 0 and one that starts at 1. We'd prefer to be able to think of these as
26// the same induction variable, with uses inside the loop using the
27// "pre-incremented" value, and uses after the loop using the
28// "post-incremented" value.
29//
30// Expressions for post-incremented uses are represented as an expression
31// paired with a set of loops for which the expression is in "post-increment"
32// mode (there may be multiple loops).
33//
34//===----------------------------------------------------------------------===//
35
36#ifndef LLVM_ANALYSIS_SCALAREVOLUTIONNORMALIZATION_H
37#define LLVM_ANALYSIS_SCALAREVOLUTIONNORMALIZATION_H
38
39#include "llvm/ADT/STLExtras.h"
40#include "llvm/ADT/SmallPtrSet.h"
41#include "llvm/Analysis/ScalarEvolutionExpressions.h"
42
43namespace llvm {
44
45class Loop;
46class ScalarEvolution;
47class SCEV;
48
49typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet;
50
51typedef function_ref<bool(const SCEVAddRecExpr *)> NormalizePredTy;
52
53/// Normalize \p S to be post-increment for all loops present in \p
54/// Loops.
55const SCEV *normalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops,
56                                   ScalarEvolution &SE);
57
58/// Normalize \p S for all add recurrence sub-expressions for which \p
59/// Pred returns true.
60const SCEV *normalizeForPostIncUseIf(const SCEV *S, NormalizePredTy Pred,
61                                     ScalarEvolution &SE);
62
63/// Denormalize \p S to be post-increment for all loops present in \p
64/// Loops.
65const SCEV *denormalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops,
66                                     ScalarEvolution &SE);
67} // namespace llvm
68
69#endif
70