include/llvm/Analysis/ScalarEvolutionNormalization.h

   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 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
  41
  42 namespace llvm {
  43
  44 class Loop;
  45 class ScalarEvolution;
  46 class SCEV;
  47
  48 typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet;
  49
  50 typedef function_ref<bool(const SCEVAddRecExpr *)> NormalizePredTy;
  51
  52 /// Normalize \p S to be post-increment for all loops present in \p
  53 /// Loops.
  54 const 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.
  59 const 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.
  64 const SCEV *denormalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops,
  65                                      ScalarEvolution &SE);
  66 } // namespace llvm
  67
  68 #endif