1 //===- LoopUnrollPass.h -----------------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H 10 #define LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H 11 12 #include "llvm/Analysis/LoopAnalysisManager.h" 13 #include "llvm/IR/PassManager.h" 14 #include "llvm/Support/CommandLine.h" 15 #include <optional> 16 17 namespace llvm { 18 19 extern cl::opt<bool> ForgetSCEVInLoopUnroll; 20 21 class Function; 22 class Loop; 23 class LPMUpdater; 24 25 /// Loop unroll pass that only does full loop unrolling and peeling. 26 class LoopFullUnrollPass : public PassInfoMixin<LoopFullUnrollPass> { 27 const int OptLevel; 28 29 /// If false, use a cost model to determine whether unrolling of a loop is 30 /// profitable. If true, only loops that explicitly request unrolling via 31 /// metadata are considered. All other loops are skipped. 32 const bool OnlyWhenForced; 33 34 /// If true, forget all loops when unrolling. If false, forget top-most loop 35 /// of the currently processed loops, which removes one entry at a time from 36 /// the internal SCEV records. For large loops, the former is faster. 37 const bool ForgetSCEV; 38 39 public: 40 explicit LoopFullUnrollPass(int OptLevel = 2, bool OnlyWhenForced = false, 41 bool ForgetSCEV = false) OptLevel(OptLevel)42 : OptLevel(OptLevel), OnlyWhenForced(OnlyWhenForced), 43 ForgetSCEV(ForgetSCEV) {} 44 45 PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM, 46 LoopStandardAnalysisResults &AR, LPMUpdater &U); 47 }; 48 49 /// A set of parameters used to control various transforms performed by the 50 /// LoopUnroll pass. Each of the boolean parameters can be set to: 51 /// true - enabling the transformation. 52 /// false - disabling the transformation. 53 /// None - relying on a global default. 54 /// 55 /// There is also OptLevel parameter, which is used for additional loop unroll 56 /// tuning. 57 /// 58 /// Intended use is to create a default object, modify parameters with 59 /// additional setters and then pass it to LoopUnrollPass. 60 /// 61 struct LoopUnrollOptions { 62 std::optional<bool> AllowPartial; 63 std::optional<bool> AllowPeeling; 64 std::optional<bool> AllowRuntime; 65 std::optional<bool> AllowUpperBound; 66 std::optional<bool> AllowProfileBasedPeeling; 67 std::optional<unsigned> FullUnrollMaxCount; 68 int OptLevel; 69 70 /// If false, use a cost model to determine whether unrolling of a loop is 71 /// profitable. If true, only loops that explicitly request unrolling via 72 /// metadata are considered. All other loops are skipped. 73 bool OnlyWhenForced; 74 75 /// If true, forget all loops when unrolling. If false, forget top-most loop 76 /// of the currently processed loops, which removes one entry at a time from 77 /// the internal SCEV records. For large loops, the former is faster. 78 const bool ForgetSCEV; 79 80 LoopUnrollOptions(int OptLevel = 2, bool OnlyWhenForced = false, 81 bool ForgetSCEV = false) OptLevelLoopUnrollOptions82 : OptLevel(OptLevel), OnlyWhenForced(OnlyWhenForced), 83 ForgetSCEV(ForgetSCEV) {} 84 85 /// Enables or disables partial unrolling. When disabled only full unrolling 86 /// is allowed. setPartialLoopUnrollOptions87 LoopUnrollOptions &setPartial(bool Partial) { 88 AllowPartial = Partial; 89 return *this; 90 } 91 92 /// Enables or disables unrolling of loops with runtime trip count. setRuntimeLoopUnrollOptions93 LoopUnrollOptions &setRuntime(bool Runtime) { 94 AllowRuntime = Runtime; 95 return *this; 96 } 97 98 /// Enables or disables loop peeling. setPeelingLoopUnrollOptions99 LoopUnrollOptions &setPeeling(bool Peeling) { 100 AllowPeeling = Peeling; 101 return *this; 102 } 103 104 /// Enables or disables the use of trip count upper bound 105 /// in loop unrolling. setUpperBoundLoopUnrollOptions106 LoopUnrollOptions &setUpperBound(bool UpperBound) { 107 AllowUpperBound = UpperBound; 108 return *this; 109 } 110 111 // Sets "optimization level" tuning parameter for loop unrolling. setOptLevelLoopUnrollOptions112 LoopUnrollOptions &setOptLevel(int O) { 113 OptLevel = O; 114 return *this; 115 } 116 117 // Enables or disables loop peeling basing on profile. setProfileBasedPeelingLoopUnrollOptions118 LoopUnrollOptions &setProfileBasedPeeling(int O) { 119 AllowProfileBasedPeeling = O; 120 return *this; 121 } 122 123 // Sets the max full unroll count. setFullUnrollMaxCountLoopUnrollOptions124 LoopUnrollOptions &setFullUnrollMaxCount(unsigned O) { 125 FullUnrollMaxCount = O; 126 return *this; 127 } 128 }; 129 130 /// Loop unroll pass that will support both full and partial unrolling. 131 /// It is a function pass to have access to function and module analyses. 132 /// It will also put loops into canonical form (simplified and LCSSA). 133 class LoopUnrollPass : public PassInfoMixin<LoopUnrollPass> { 134 LoopUnrollOptions UnrollOpts; 135 136 public: 137 /// This uses the target information (or flags) to control the thresholds for 138 /// different unrolling stategies but supports all of them. 139 explicit LoopUnrollPass(LoopUnrollOptions UnrollOpts = {}) UnrollOpts(UnrollOpts)140 : UnrollOpts(UnrollOpts) {} 141 142 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); 143 void printPipeline(raw_ostream &OS, 144 function_ref<StringRef(StringRef)> MapClassName2PassName); 145 }; 146 147 } // end namespace llvm 148 149 #endif // LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H 150