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0001 //===- llvm/Analysis/ScalarEvolutionNormalization.h - See below -*- C++ -*-===// 0002 // 0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 0004 // See https://llvm.org/LICENSE.txt for license information. 0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 0006 // 0007 //===----------------------------------------------------------------------===// 0008 // 0009 // This file defines utilities for working with "normalized" ScalarEvolution 0010 // expressions. 0011 // 0012 // The following example illustrates post-increment uses and how normalized 0013 // expressions help. 0014 // 0015 // for (i=0; i!=n; ++i) { 0016 // ... 0017 // } 0018 // use(i); 0019 // 0020 // While the expression for most uses of i inside the loop is {0,+,1}<%L>, the 0021 // expression for the use of i outside the loop is {1,+,1}<%L>, since i is 0022 // incremented at the end of the loop body. This is inconveient, since it 0023 // suggests that we need two different induction variables, one that starts 0024 // at 0 and one that starts at 1. We'd prefer to be able to think of these as 0025 // the same induction variable, with uses inside the loop using the 0026 // "pre-incremented" value, and uses after the loop using the 0027 // "post-incremented" value. 0028 // 0029 // Expressions for post-incremented uses are represented as an expression 0030 // paired with a set of loops for which the expression is in "post-increment" 0031 // mode (there may be multiple loops). 0032 // 0033 //===----------------------------------------------------------------------===// 0034 0035 #ifndef LLVM_ANALYSIS_SCALAREVOLUTIONNORMALIZATION_H 0036 #define LLVM_ANALYSIS_SCALAREVOLUTIONNORMALIZATION_H 0037 0038 #include "llvm/ADT/STLFunctionalExtras.h" 0039 #include "llvm/ADT/SmallPtrSet.h" 0040 0041 namespace llvm { 0042 0043 class Loop; 0044 class ScalarEvolution; 0045 class SCEV; 0046 class SCEVAddRecExpr; 0047 0048 typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet; 0049 0050 typedef function_ref<bool(const SCEVAddRecExpr *)> NormalizePredTy; 0051 0052 /// Normalize \p S to be post-increment for all loops present in \p 0053 /// Loops. Returns nullptr if the result is not invertible and \p 0054 /// CheckInvertible is true. 0055 const SCEV *normalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops, 0056 ScalarEvolution &SE, 0057 bool CheckInvertible = true); 0058 0059 /// Normalize \p S for all add recurrence sub-expressions for which \p 0060 /// Pred returns true. 0061 const SCEV *normalizeForPostIncUseIf(const SCEV *S, NormalizePredTy Pred, 0062 ScalarEvolution &SE); 0063 0064 /// Denormalize \p S to be post-increment for all loops present in \p 0065 /// Loops. 0066 const SCEV *denormalizeForPostIncUse(const SCEV *S, const PostIncLoopSet &Loops, 0067 ScalarEvolution &SE); 0068 } // namespace llvm 0069 0070 #endif
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