1//===- llvm/Analysis/ScalarEvolutionNormalization.h - See below -*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines utilities for working with "normalized" ScalarEvolution
10// expressions.
11//
12// The following example illustrates post-increment uses and how normalized
13// expressions help.
14//
15//   for (i=0; i!=n; ++i) {
16//     ...
17//   }
18//   use(i);
19//
20// While the expression for most uses of i inside the loop is {0,+,1}<%L>, the
21// expression for the use of i outside the loop is {1,+,1}<%L>, since i is
22// incremented at the end of the loop body. This is inconveient, since it
23// suggests that we need two different induction variables, one that starts
24// at 0 and one that starts at 1. We'd prefer to be able to think of these as
25// the same induction variable, with uses inside the loop using the
26// "pre-incremented" value, and uses after the loop using the
27// "post-incremented" value.
28//
29// Expressions for post-incremented uses are represented as an expression
30// paired with a set of loops for which the expression is in "post-increment"
31// mode (there may be multiple loops).
32//
33//===----------------------------------------------------------------------===//
34
35#ifndef LLVM_ANALYSIS_SCALAREVOLUTIONNORMALIZATION_H
36#define LLVM_ANALYSIS_SCALAREVOLUTIONNORMALIZATION_H
37
38#include "llvm/ADT/STLExtras.h"
39#include "llvm/ADT/SmallPtrSet.h"
40
41namespace llvm {
42
43class Loop;
44class ScalarEvolution;
45class SCEV;
46class SCEVAddRecExpr;
47
48typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet;
49
50typedef function_ref<bool(const SCEVAddRecExpr *)> NormalizePredTy;
51
52/// Normalize \p S to be post-increment for all loops present in \p
53/// Loops.
54const SCEV *normalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops,
55                                   ScalarEvolution &SE);
56
57/// Normalize \p S for all add recurrence sub-expressions for which \p
58/// Pred returns true.
59const SCEV *normalizeForPostIncUseIf(const SCEV *S, NormalizePredTy Pred,
60                                     ScalarEvolution &SE);
61
62/// Denormalize \p S to be post-increment for all loops present in \p
63/// Loops.
64const SCEV *denormalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops,
65                                     ScalarEvolution &SE);
66} // namespace llvm
67
68#endif
69