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
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 and peeling.
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 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)
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 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

source code of llvm/include/llvm/Transforms/Scalar/LoopUnrollPass.h