include/llvm/Transforms/Scalar/LoopUnrollPass.h

   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/ADT/Optional.h"
  13 #include "llvm/Analysis/LoopAnalysisManager.h"
  14 #include "llvm/IR/PassManager.h"
  15
  16 namespace llvm {
  17
  18 extern cl::opt<bool> ForgetSCEVInLoopUnroll;
  19
  20 class Function;
  21 class Loop;
  22 class LPMUpdater;
  23
  24 /// Loop unroll pass that only does full loop unrolling.
  25 class LoopFullUnrollPass : public PassInfoMixin<LoopFullUnrollPass> {
  26   const int OptLevel;
  27
  28   /// If false, use a cost model to determine whether unrolling of a loop is
  29   /// profitable. If true, only loops that explicitly request unrolling via
  30   /// metadata are considered. All other loops are skipped.
  31   const bool OnlyWhenForced;
  32
  33   /// If true, forget all loops when unrolling. If false, forget top-most loop
  34   /// of the currently processed loops, which removes one entry at a time from
  35   /// the internal SCEV records. For large loops, the former is faster.
  36   const bool ForgetSCEV;
  37
  38 public:
  39   explicit LoopFullUnrollPass(int OptLevel = 2, bool OnlyWhenForced = false,
  40                               bool ForgetSCEV = false)
  41       : OptLevel(OptLevel), OnlyWhenForced(OnlyWhenForced),
  42         ForgetSCEV(ForgetSCEV) {}
  43
  44   PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM,
  45                         LoopStandardAnalysisResults &AR, LPMUpdater &U);
  46 };
  47
  48 /// A set of parameters used to control various transforms performed by the
  49 /// LoopUnroll pass. Each of the boolean parameters can be set to:
  50 ///      true - enabling the transformation.
  51 ///      false - disabling the transformation.
  52 ///      None - relying on a global default.
  53 ///
  54 /// There is also OptLevel parameter, which is used for additional loop unroll
  55 /// tuning.
  56 ///
  57 /// Intended use is to create a default object, modify parameters with
  58 /// additional setters and then pass it to LoopUnrollPass.
  59 ///
  60 struct LoopUnrollOptions {
  61   Optional<bool> AllowPartial;
  62   Optional<bool> AllowPeeling;
  63   Optional<bool> AllowRuntime;
  64   Optional<bool> AllowUpperBound;
  65   Optional<bool> AllowProfileBasedPeeling;
  66   int OptLevel;
  67
  68   /// If false, use a cost model to determine whether unrolling of a loop is
  69   /// profitable. If true, only loops that explicitly request unrolling via
  70   /// metadata are considered. All other loops are skipped.
  71   bool OnlyWhenForced;
  72
  73   /// If true, forget all loops when unrolling. If false, forget top-most loop
  74   /// of the currently processed loops, which removes one entry at a time from
  75   /// the internal SCEV records. For large loops, the former is faster.
  76   const bool ForgetSCEV;
  77
  78   LoopUnrollOptions(int OptLevel = 2, bool OnlyWhenForced = false,
  79                     bool ForgetSCEV = false)
  80       : OptLevel(OptLevel), OnlyWhenForced(OnlyWhenForced),
  81         ForgetSCEV(ForgetSCEV) {}
  82
  83   /// Enables or disables partial unrolling. When disabled only full unrolling
  84   /// is allowed.
  85   LoopUnrollOptions &setPartial(bool Partial) {
  86     AllowPartial = Partial;
  87     return *this;
  88   }
  89
  90   /// Enables or disables unrolling of loops with runtime trip count.
  91   LoopUnrollOptions &setRuntime(bool Runtime) {
  92     AllowRuntime = Runtime;
  93     return *this;
  94   }
  95
  96   /// Enables or disables loop peeling.
  97   LoopUnrollOptions &setPeeling(bool Peeling) {
  98     AllowPeeling = Peeling;
  99     return *this;
 100   }
 101
 102   /// Enables or disables the use of trip count upper bound
 103   /// in loop unrolling.
 104   LoopUnrollOptions &setUpperBound(bool UpperBound) {
 105     AllowUpperBound = UpperBound;
 106     return *this;
 107   }
 108
 109   // Sets "optimization level" tuning parameter for loop unrolling.
 110   LoopUnrollOptions &setOptLevel(int O) {
 111     OptLevel = O;
 112     return *this;
 113   }
 114
 115   // Enables or disables loop peeling basing on profile.
 116   LoopUnrollOptions &setProfileBasedPeeling(int O) {
 117     AllowProfileBasedPeeling = O;
 118     return *this;
 119   }
 120 };
 121
 122 /// Loop unroll pass that will support both full and partial unrolling.
 123 /// It is a function pass to have access to function and module analyses.
 124 /// It will also put loops into canonical form (simplified and LCSSA).
 125 class LoopUnrollPass : public PassInfoMixin<LoopUnrollPass> {
 126   LoopUnrollOptions UnrollOpts;
 127
 128 public:
 129   /// This uses the target information (or flags) to control the thresholds for
 130   /// different unrolling stategies but supports all of them.
 131   explicit LoopUnrollPass(LoopUnrollOptions UnrollOpts = {})
 132       : UnrollOpts(UnrollOpts) {}
 133
 134   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 135 };
 136
 137 } // end namespace llvm
 138
 139 #endif // LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H