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When we have a loop with a known upper bound on the number of iterations, and furthermore know that either the number of iterations will be either exactly that upper bound or zero, then we can fully unroll up to that upper bound keeping only the first loop test to check for the zero iteration case. Most of the work here is in plumbing this 'max-or-zero' information from the part of scalar evolution where it's detected through to loop unrolling. I've also gone for the safe default of 'false' everywhere but howManyLessThans which could probably be improved. Differential Revision: https://reviews.llvm.org/D25682 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284818 91177308-0d34-0410-b5e6-96231b3b80d8
50 lines
1.6 KiB
C++
50 lines
1.6 KiB
C++
//===- llvm/Transforms/Utils/UnrollLoop.h - Unrolling utilities -*- 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 some loop unrolling utilities. It does not define any
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// actual pass or policy, but provides a single function to perform loop
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// unrolling.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_UNROLLLOOP_H
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#define LLVM_TRANSFORMS_UTILS_UNROLLLOOP_H
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namespace llvm {
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class StringRef;
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class AssumptionCache;
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class DominatorTree;
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class Loop;
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class LoopInfo;
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class LPPassManager;
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class MDNode;
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class Pass;
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class OptimizationRemarkEmitter;
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class ScalarEvolution;
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bool UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force,
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bool AllowRuntime, bool AllowExpensiveTripCount,
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bool PreserveCondBr, bool PreserveOnlyFirst,
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unsigned TripMultiple, LoopInfo *LI, ScalarEvolution *SE,
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DominatorTree *DT, AssumptionCache *AC,
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OptimizationRemarkEmitter *ORE, bool PreserveLCSSA);
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bool UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
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bool AllowExpensiveTripCount,
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bool UseEpilogRemainder, LoopInfo *LI,
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ScalarEvolution *SE, DominatorTree *DT,
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bool PreserveLCSSA);
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MDNode *GetUnrollMetadata(MDNode *LoopID, StringRef Name);
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}
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#endif
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