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#include "llvm/Support/CommandLine.h"
16
17namespace llvm {
18
19extern cl::opt<bool> ForgetSCEVInLoopUnroll;
20
21class Function;
22class Loop;
23class LPMUpdater;
24
25/// Loop unroll pass that only does full loop unrolling.
26class 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
39public:
40  explicit LoopFullUnrollPass(int OptLevel = 2, bool OnlyWhenForced = false,
41                              bool ForgetSCEV = false)
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///
61struct LoopUnrollOptions {
62  Optional<bool> AllowPartial;
63  Optional<bool> AllowPeeling;
64  Optional<bool> AllowRuntime;
65  Optional<bool> AllowUpperBound;
66  Optional<bool> AllowProfileBasedPeeling;
67  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)
82      : OptLevel(OptLevel), OnlyWhenForced(OnlyWhenForced),
83        ForgetSCEV(ForgetSCEV) {}
84
85  /// Enables or disables partial unrolling. When disabled only full unrolling
86  /// is allowed.
87  LoopUnrollOptions &setPartial(bool Partial) {
88    AllowPartial = Partial;
89    return *this;
90  }
91
92  /// Enables or disables unrolling of loops with runtime trip count.
93  LoopUnrollOptions &setRuntime(bool Runtime) {
94    AllowRuntime = Runtime;
95    return *this;
96  }
97
98  /// Enables or disables loop peeling.
99  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.
106  LoopUnrollOptions &setUpperBound(bool UpperBound) {
107    AllowUpperBound = UpperBound;
108    return *this;
109  }
110
111  // Sets "optimization level" tuning parameter for loop unrolling.
112  LoopUnrollOptions &setOptLevel(int O) {
113    OptLevel = O;
114    return *this;
115  }
116
117  // Enables or disables loop peeling basing on profile.
118  LoopUnrollOptions &setProfileBasedPeeling(int O) {
119    AllowProfileBasedPeeling = O;
120    return *this;
121  }
122
123  // Sets the max full unroll count.
124  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).
133class LoopUnrollPass : public PassInfoMixin<LoopUnrollPass> {
134  LoopUnrollOptions UnrollOpts;
135
136public:
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 = {})
140      : UnrollOpts(UnrollOpts) {}
141
142  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
143};
144
145} // end namespace llvm
146
147#endif // LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H
148