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      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 
     41 namespace llvm {
     42 
     43 class Loop;
     44 class ScalarEvolution;
     45 class SCEV;
     46 class SCEVAddRecExpr;
     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
     69