1 //===- LoopUnrollPass.h -----------------------------------------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 #ifndef LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H
10 #define LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H
12 #include "llvm/ADT/Optional.h"
13 #include "llvm/Analysis/LoopAnalysisManager.h"
14 #include "llvm/IR/PassManager.h"
18 extern cl::opt<bool> ForgetSCEVInLoopUnroll;
24 /// Loop unroll pass that only does full loop unrolling.
25 class LoopFullUnrollPass : public PassInfoMixin<LoopFullUnrollPass> {
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;
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;
39 explicit LoopFullUnrollPass(int OptLevel = 2, bool OnlyWhenForced = false,
40 bool ForgetSCEV = false)
41 : OptLevel(OptLevel), OnlyWhenForced(OnlyWhenForced),
42 ForgetSCEV(ForgetSCEV) {}
44 PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM,
45 LoopStandardAnalysisResults &AR, LPMUpdater &U);
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.
54 /// There is also OptLevel parameter, which is used for additional loop unroll
57 /// Intended use is to create a default object, modify parameters with
58 /// additional setters and then pass it to LoopUnrollPass.
60 struct LoopUnrollOptions {
61 Optional<bool> AllowPartial;
62 Optional<bool> AllowPeeling;
63 Optional<bool> AllowRuntime;
64 Optional<bool> AllowUpperBound;
67 /// If false, use a cost model to determine whether unrolling of a loop is
68 /// profitable. If true, only loops that explicitly request unrolling via
69 /// metadata are considered. All other loops are skipped.
72 /// If true, forget all loops when unrolling. If false, forget top-most loop
73 /// of the currently processed loops, which removes one entry at a time from
74 /// the internal SCEV records. For large loops, the former is faster.
75 const bool ForgetSCEV;
77 LoopUnrollOptions(int OptLevel = 2, bool OnlyWhenForced = false,
78 bool ForgetSCEV = false)
79 : OptLevel(OptLevel), OnlyWhenForced(OnlyWhenForced),
80 ForgetSCEV(ForgetSCEV) {}
82 /// Enables or disables partial unrolling. When disabled only full unrolling
84 LoopUnrollOptions &setPartial(bool Partial) {
85 AllowPartial = Partial;
89 /// Enables or disables unrolling of loops with runtime trip count.
90 LoopUnrollOptions &setRuntime(bool Runtime) {
91 AllowRuntime = Runtime;
95 /// Enables or disables loop peeling.
96 LoopUnrollOptions &setPeeling(bool Peeling) {
97 AllowPeeling = Peeling;
101 /// Enables or disables the use of trip count upper bound
102 /// in loop unrolling.
103 LoopUnrollOptions &setUpperBound(bool UpperBound) {
104 AllowUpperBound = UpperBound;
108 // Sets "optimization level" tuning parameter for loop unrolling.
109 LoopUnrollOptions &setOptLevel(int O) {
115 /// Loop unroll pass that will support both full and partial unrolling.
116 /// It is a function pass to have access to function and module analyses.
117 /// It will also put loops into canonical form (simplified and LCSSA).
118 class LoopUnrollPass : public PassInfoMixin<LoopUnrollPass> {
119 LoopUnrollOptions UnrollOpts;
122 /// This uses the target information (or flags) to control the thresholds for
123 /// different unrolling stategies but supports all of them.
124 explicit LoopUnrollPass(LoopUnrollOptions UnrollOpts = {})
125 : UnrollOpts(UnrollOpts) {}
127 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
130 } // end namespace llvm
132 #endif // LLVM_TRANSFORMS_SCALAR_LOOPUNROLLPASS_H