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File indexing completed on 2026-05-10 08:44:43
0001 //===- LoopSimplify.h - Loop Canonicalization Pass --------------*- 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 pass performs several transformations to transform natural loops into a 0010 // simpler form, which makes subsequent analyses and transformations simpler and 0011 // more effective. 0012 // 0013 // Loop pre-header insertion guarantees that there is a single, non-critical 0014 // entry edge from outside of the loop to the loop header. This simplifies a 0015 // number of analyses and transformations, such as LICM. 0016 // 0017 // Loop exit-block insertion guarantees that all exit blocks from the loop 0018 // (blocks which are outside of the loop that have predecessors inside of the 0019 // loop) only have predecessors from inside of the loop (and are thus dominated 0020 // by the loop header). This simplifies transformations such as store-sinking 0021 // that are built into LICM. 0022 // 0023 // This pass also guarantees that loops will have exactly one backedge. 0024 // 0025 // Indirectbr instructions introduce several complications. If the loop 0026 // contains or is entered by an indirectbr instruction, it may not be possible 0027 // to transform the loop and make these guarantees. Client code should check 0028 // that these conditions are true before relying on them. 0029 // 0030 // Note that the simplifycfg pass will clean up blocks which are split out but 0031 // end up being unnecessary, so usage of this pass should not pessimize 0032 // generated code. 0033 // 0034 // This pass obviously modifies the CFG, but updates loop information and 0035 // dominator information. 0036 // 0037 //===----------------------------------------------------------------------===// 0038 #ifndef LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H 0039 #define LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H 0040 0041 #include "llvm/IR/PassManager.h" 0042 0043 namespace llvm { 0044 0045 class AssumptionCache; 0046 class DominatorTree; 0047 class Loop; 0048 class LoopInfo; 0049 class MemorySSAUpdater; 0050 class ScalarEvolution; 0051 0052 /// This pass is responsible for loop canonicalization. 0053 class LoopSimplifyPass : public PassInfoMixin<LoopSimplifyPass> { 0054 public: 0055 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); 0056 }; 0057 0058 /// Simplify each loop in a loop nest recursively. 0059 /// 0060 /// This takes a potentially un-simplified loop L (and its children) and turns 0061 /// it into a simplified loop nest with preheaders and single backedges. It will 0062 /// update \c DominatorTree, \c LoopInfo, \c ScalarEvolution and \c MemorySSA 0063 /// analyses if they're non-null, and LCSSA if \c PreserveLCSSA is true. 0064 bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, 0065 AssumptionCache *AC, MemorySSAUpdater *MSSAU, 0066 bool PreserveLCSSA); 0067 0068 } // end namespace llvm 0069 0070 #endif // LLVM_TRANSFORMS_UTILS_LOOPSIMPLIFY_H
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