ScalarEvolutionNormalization.h revision 448db1cdef5872713ef77beffacf502ae3450cd7 
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_SCALAREVOLUTION_NORMALIZATION_H
37#define LLVM_ANALYSIS_SCALAREVOLUTION_NORMALIZATION_H
38
39#include "llvm/ADT/SmallPtrSet.h"
40
41namespace llvm {
42
43class Instruction;
44class DominatorTree;
45class Loop;
46class ScalarEvolution;
47class SCEV;
48class Value;
49
50/// TransformKind - Different types of transformations that
51/// TransformForPostIncUse can do.
52enum TransformKind {
53  /// Normalize - Normalize according to the given loops.
54  Normalize,
55  /// NormalizeAutodetect - Detect post-inc opportunities on new expressions,
56  /// update the given loop set, and normalize.
57  NormalizeAutodetect,
58  /// Denormalize - Perform the inverse transform on the expression with the
59  /// given loop set.
60  Denormalize
61};
62
63/// PostIncLoopSet - A set of loops.
64typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet;
65
66/// TransformForPostIncUse - Transform the given expression according to the
67/// given transformation kind.
68const SCEV *TransformForPostIncUse(TransformKind Kind,
69                                   const SCEV *S,
70                                   Instruction *User,
71                                   Value *OperandValToReplace,
72                                   PostIncLoopSet &Loops,
73                                   ScalarEvolution &SE,
74                                   DominatorTree &DT);
75
76}
77
78#endif
79