Home | History | Annotate | Download | only in Analysis
      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_SCALAREVOLUTIONNORMALIZATION_H
     37 #define LLVM_ANALYSIS_SCALAREVOLUTIONNORMALIZATION_H
     38 
     39 #include "llvm/ADT/SmallPtrSet.h"
     40 
     41 namespace llvm {
     42 
     43 class Instruction;
     44 class DominatorTree;
     45 class Loop;
     46 class ScalarEvolution;
     47 class SCEV;
     48 class Value;
     49 
     50 /// TransformKind - Different types of transformations that
     51 /// TransformForPostIncUse can do.
     52 enum 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.
     64 typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet;
     65 
     66 /// TransformForPostIncUse - Transform the given expression according to the
     67 /// given transformation kind.
     68 const 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