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65 lines
2.7 KiB
C++
65 lines
2.7 KiB
C++
//===- LoopSimplify.h - Loop Canonicalization Pass --------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass performs several transformations to transform natural loops into a
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// simpler form, which makes subsequent analyses and transformations simpler and
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// more effective.
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//
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// Loop pre-header insertion guarantees that there is a single, non-critical
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// entry edge from outside of the loop to the loop header. This simplifies a
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// number of analyses and transformations, such as LICM.
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//
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// Loop exit-block insertion guarantees that all exit blocks from the loop
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// (blocks which are outside of the loop that have predecessors inside of the
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// loop) only have predecessors from inside of the loop (and are thus dominated
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// by the loop header). This simplifies transformations such as store-sinking
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// that are built into LICM.
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//
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// This pass also guarantees that loops will have exactly one backedge.
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//
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// Indirectbr instructions introduce several complications. If the loop
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// contains or is entered by an indirectbr instruction, it may not be possible
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// to transform the loop and make these guarantees. Client code should check
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// that these conditions are true before relying on them.
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//
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// Note that the simplifycfg pass will clean up blocks which are split out but
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// end up being unnecessary, so usage of this pass should not pessimize
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// generated code.
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//
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// This pass obviously modifies the CFG, but updates loop information and
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// dominator information.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
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#define LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/Analysis/ScalarEvolution.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/PassManager.h"
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namespace llvm {
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/// This pass is responsible for loop canonicalization.
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class LoopSimplifyPass : public PassInfoMixin<LoopSimplifyPass> {
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public:
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
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};
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/// Simplify each loop in a loop nest recursively.
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///
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/// This takes a potentially un-simplified loop L (and its children) and turns
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/// it into a simplified loop nest with preheaders and single backedges. It will
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/// update \c AliasAnalysis and \c ScalarEvolution analyses if they're non-null.
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bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE,
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AssumptionCache *AC, bool PreserveLCSSA);
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
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