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LoopUnrollPass.h
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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"
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 
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 ///
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.
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.
111  OptLevel = O;
112  return *this;
113  }
114 
115  // Enables or disables loop peeling basing on profile.
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 
135 };
136 
137 } // end namespace llvm
138 
139 #endif // LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H
A set of parameters used to control various transforms performed by the LoopUnroll pass...
This class represents lattice values for constants.
Definition: AllocatorList.h:23
bool OnlyWhenForced
If false, use a cost model to determine whether unrolling of a loop is profitable.
cl::opt< bool > ForgetSCEVInLoopUnroll
LoopUnrollOptions & setUpperBound(bool UpperBound)
Enables or disables the use of trip count upper bound in loop unrolling.
The adaptor from a function pass to a loop pass computes these analyses and makes them available to t...
F(f)
Loop unroll pass that only does full loop unrolling.
Loop unroll pass that will support both full and partial unrolling.
Optional< bool > AllowProfileBasedPeeling
Optional< bool > AllowPeeling
A CRTP mix-in to automatically provide informational APIs needed for passes.
Definition: PassManager.h:372
This header provides classes for managing per-loop analyses.
LoopUnrollOptions & setPartial(bool Partial)
Enables or disables partial unrolling.
LoopUnrollOptions(int OptLevel=2, bool OnlyWhenForced=false, bool ForgetSCEV=false)
LoopUnrollPass(LoopUnrollOptions UnrollOpts={})
This uses the target information (or flags) to control the thresholds for different unrolling stategi...
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:153
const bool ForgetSCEV
If true, forget all loops when unrolling.
PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM, LoopStandardAnalysisResults &AR, LPMUpdater &U)
LoopUnrollOptions & setProfileBasedPeeling(int O)
LoopUnrollOptions & setOptLevel(int O)
This class provides an interface for updating the loop pass manager based on mutations to the loop ne...
LoopFullUnrollPass(int OptLevel=2, bool OnlyWhenForced=false, bool ForgetSCEV=false)
Optional< bool > AllowPartial
Optional< bool > AllowUpperBound
LoopUnrollOptions & setRuntime(bool Runtime)
Enables or disables unrolling of loops with runtime trip count.
Represents a single loop in the control flow graph.
Definition: LoopInfo.h:509
A container for analyses that lazily runs them and caches their results.
Optional< bool > AllowRuntime
This header defines various interfaces for pass management in LLVM.
LoopUnrollOptions & setPeeling(bool Peeling)
Enables or disables loop peeling.