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b5210c934f
explicitly split into stride-and-offset pairs. Also, add the ability to track multiple post-increment loops on the same expression. This refines the concept of "normalizing" SCEV expressions used for to post-increment uses, and introduces a dedicated utility routine for normalizing and denormalizing expressions. This fixes the expansion of expressions which are post-increment users of more than one loop at a time. More broadly, this takes LSR another step closer to being able to reason about more than one loop at a time. llvm-svn: 100699
79 lines
2.7 KiB
C++
79 lines
2.7 KiB
C++
//===- llvm/Analysis/ScalarEvolutionNormalization.h - See below -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines utilities for working with "normalized" ScalarEvolution
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// expressions.
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//
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// The following example illustrates post-increment uses and how normalized
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// expressions help.
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//
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// for (i=0; i!=n; ++i) {
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// ...
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// }
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// use(i);
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//
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// While the expression for most uses of i inside the loop is {0,+,1}<%L>, the
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// expression for the use of i outside the loop is {1,+,1}<%L>, since i is
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// incremented at the end of the loop body. This is inconveient, since it
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// suggests that we need two different induction variables, one that starts
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// at 0 and one that starts at 1. We'd prefer to be able to think of these as
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// the same induction variable, with uses inside the loop using the
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// "pre-incremented" value, and uses after the loop using the
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// "post-incremented" value.
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//
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// Expressions for post-incremented uses are represented as an expression
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// paired with a set of loops for which the expression is in "post-increment"
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// mode (there may be multiple loops).
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_SCALAREVOLUTION_NORMALIZATION_H
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#define LLVM_ANALYSIS_SCALAREVOLUTION_NORMALIZATION_H
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#include "llvm/ADT/SmallPtrSet.h"
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namespace llvm {
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class Instruction;
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class DominatorTree;
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class Loop;
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class ScalarEvolution;
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class SCEV;
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class Value;
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/// TransformKind - Different types of transformations that
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/// TransformForPostIncUse can do.
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enum TransformKind {
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/// Normalize - Normalize according to the given loops.
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Normalize,
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/// NormalizeAutodetect - Detect post-inc opportunities on new expressions,
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/// update the given loop set, and normalize.
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NormalizeAutodetect,
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/// Denormalize - Perform the inverse transform on the expression with the
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/// given loop set.
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Denormalize
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};
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/// PostIncLoopSet - A set of loops.
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typedef SmallPtrSet<const Loop *, 2> PostIncLoopSet;
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/// TransformForPostIncUse - Transform the given expression according to the
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/// given transformation kind.
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const SCEV *TransformForPostIncUse(TransformKind Kind,
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const SCEV *S,
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Instruction *User,
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Value *OperandValToReplace,
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PostIncLoopSet &Loops,
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ScalarEvolution &SE,
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DominatorTree &DT);
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}
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#endif
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