1//===- LoopVectorize.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// This is the LLVM loop vectorizer. This pass modifies 'vectorizable' loops
10// and generates target-independent LLVM-IR.
11// The vectorizer uses the TargetTransformInfo analysis to estimate the costs
12// of instructions in order to estimate the profitability of vectorization.
13//
14// The loop vectorizer combines consecutive loop iterations into a single
15// 'wide' iteration. After this transformation the index is incremented
16// by the SIMD vector width, and not by one.
17//
18// This pass has four parts:
19// 1. The main loop pass that drives the different parts.
20// 2. LoopVectorizationLegality - A unit that checks for the legality
21// of the vectorization.
22// 3. InnerLoopVectorizer - A unit that performs the actual
23// widening of instructions.
24// 4. LoopVectorizationCostModel - A unit that checks for the profitability
25// of vectorization. It decides on the optimal vector width, which
26// can be one, if vectorization is not profitable.
27//
28// There is a development effort going on to migrate loop vectorizer to the
29// VPlan infrastructure and to introduce outer loop vectorization support (see
30// docs/VectorizationPlan.rst and
31// http://lists.llvm.org/pipermail/llvm-dev/2017-December/119523.html). For this
32// purpose, we temporarily introduced the VPlan-native vectorization path: an
33// alternative vectorization path that is natively implemented on top of the
34// VPlan infrastructure. See EnableVPlanNativePath for enabling.
35//
36//===----------------------------------------------------------------------===//
37//
38// The reduction-variable vectorization is based on the paper:
39// D. Nuzman and R. Henderson. Multi-platform Auto-vectorization.
40//
41// Variable uniformity checks are inspired by:
42// Karrenberg, R. and Hack, S. Whole Function Vectorization.
43//
44// The interleaved access vectorization is based on the paper:
45// Dorit Nuzman, Ira Rosen and Ayal Zaks. Auto-Vectorization of Interleaved
46// Data for SIMD
47//
48// Other ideas/concepts are from:
49// A. Zaks and D. Nuzman. Autovectorization in GCC-two years later.
50//
51// S. Maleki, Y. Gao, M. Garzaran, T. Wong and D. Padua. An Evaluation of
52// Vectorizing Compilers.
53//
54//===----------------------------------------------------------------------===//
55
56#ifndef LLVM_TRANSFORMS_VECTORIZE_LOOPVECTORIZE_H
57#define LLVM_TRANSFORMS_VECTORIZE_LOOPVECTORIZE_H
58
59#include "llvm/IR/PassManager.h"
60#include "llvm/Support/CommandLine.h"
61#include <functional>
62
63namespace llvm {
64
65class AssumptionCache;
66class BlockFrequencyInfo;
67class DemandedBits;
68class DominatorTree;
69class Function;
70class Loop;
71class LoopAccessInfoManager;
72class LoopInfo;
73class OptimizationRemarkEmitter;
74class ProfileSummaryInfo;
75class ScalarEvolution;
76class TargetLibraryInfo;
77class TargetTransformInfo;
78
79extern cl::opt<bool> EnableLoopInterleaving;
80extern cl::opt<bool> EnableLoopVectorization;
81
82/// A marker to determine if extra passes after loop vectorization should be
83/// run.
84struct ShouldRunExtraVectorPasses
85 : public AnalysisInfoMixin<ShouldRunExtraVectorPasses> {
86 static AnalysisKey Key;
87 struct Result {
88 bool invalidate(Function &F, const PreservedAnalyses &PA,
89 FunctionAnalysisManager::Invalidator &) {
90 // Check whether the analysis has been explicitly invalidated. Otherwise,
91 // it remains preserved.
92 auto PAC = PA.getChecker<ShouldRunExtraVectorPasses>();
93 return !PAC.preservedWhenStateless();
94 }
95 };
96
97 Result run(Function &F, FunctionAnalysisManager &FAM) { return Result(); }
98};
99
100/// A pass manager to run a set of extra function simplification passes after
101/// vectorization, if requested. LoopVectorize caches the
102/// ShouldRunExtraVectorPasses analysis to request extra simplifications, if
103/// they could be beneficial.
104struct ExtraVectorPassManager : public FunctionPassManager {
105 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM) {
106 auto PA = PreservedAnalyses::all();
107 if (AM.getCachedResult<ShouldRunExtraVectorPasses>(IR&: F))
108 PA.intersect(Arg: FunctionPassManager::run(IR&: F, AM));
109 PA.abandon<ShouldRunExtraVectorPasses>();
110 return PA;
111 }
112};
113
114struct LoopVectorizeOptions {
115 /// If false, consider all loops for interleaving.
116 /// If true, only loops that explicitly request interleaving are considered.
117 bool InterleaveOnlyWhenForced;
118
119 /// If false, consider all loops for vectorization.
120 /// If true, only loops that explicitly request vectorization are considered.
121 bool VectorizeOnlyWhenForced;
122
123 /// The current defaults when creating the pass with no arguments are:
124 /// EnableLoopInterleaving = true and EnableLoopVectorization = true. This
125 /// means that interleaving default is consistent with the cl::opt flag, while
126 /// vectorization is not.
127 /// FIXME: The default for EnableLoopVectorization in the cl::opt should be
128 /// set to true, and the corresponding change to account for this be made in
129 /// opt.cpp. The initializations below will become:
130 /// InterleaveOnlyWhenForced(!EnableLoopInterleaving)
131 /// VectorizeOnlyWhenForced(!EnableLoopVectorization).
132 LoopVectorizeOptions()
133 : InterleaveOnlyWhenForced(false), VectorizeOnlyWhenForced(false) {}
134 LoopVectorizeOptions(bool InterleaveOnlyWhenForced,
135 bool VectorizeOnlyWhenForced)
136 : InterleaveOnlyWhenForced(InterleaveOnlyWhenForced),
137 VectorizeOnlyWhenForced(VectorizeOnlyWhenForced) {}
138
139 LoopVectorizeOptions &setInterleaveOnlyWhenForced(bool Value) {
140 InterleaveOnlyWhenForced = Value;
141 return *this;
142 }
143
144 LoopVectorizeOptions &setVectorizeOnlyWhenForced(bool Value) {
145 VectorizeOnlyWhenForced = Value;
146 return *this;
147 }
148};
149
150/// Storage for information about made changes.
151struct LoopVectorizeResult {
152 bool MadeAnyChange;
153 bool MadeCFGChange;
154
155 LoopVectorizeResult(bool MadeAnyChange, bool MadeCFGChange)
156 : MadeAnyChange(MadeAnyChange), MadeCFGChange(MadeCFGChange) {}
157};
158
159/// The LoopVectorize Pass.
160struct LoopVectorizePass : public PassInfoMixin<LoopVectorizePass> {
161private:
162 /// If false, consider all loops for interleaving.
163 /// If true, only loops that explicitly request interleaving are considered.
164 bool InterleaveOnlyWhenForced;
165
166 /// If false, consider all loops for vectorization.
167 /// If true, only loops that explicitly request vectorization are considered.
168 bool VectorizeOnlyWhenForced;
169
170public:
171 LoopVectorizePass(LoopVectorizeOptions Opts = {});
172
173 ScalarEvolution *SE;
174 LoopInfo *LI;
175 TargetTransformInfo *TTI;
176 DominatorTree *DT;
177 BlockFrequencyInfo *BFI;
178 TargetLibraryInfo *TLI;
179 DemandedBits *DB;
180 AssumptionCache *AC;
181 LoopAccessInfoManager *LAIs;
182 OptimizationRemarkEmitter *ORE;
183 ProfileSummaryInfo *PSI;
184
185 PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
186 void printPipeline(raw_ostream &OS,
187 function_ref<StringRef(StringRef)> MapClassName2PassName);
188
189 // Shim for old PM.
190 LoopVectorizeResult runImpl(Function &F, ScalarEvolution &SE_, LoopInfo &LI_,
191 TargetTransformInfo &TTI_, DominatorTree &DT_,
192 BlockFrequencyInfo *BFI_, TargetLibraryInfo *TLI_,
193 DemandedBits &DB_, AssumptionCache &AC_,
194 LoopAccessInfoManager &LAIs_,
195 OptimizationRemarkEmitter &ORE_,
196 ProfileSummaryInfo *PSI_);
197
198 bool processLoop(Loop *L);
199};
200
201/// Reports a vectorization failure: print \p DebugMsg for debugging
202/// purposes along with the corresponding optimization remark \p RemarkName.
203/// If \p I is passed, it is an instruction that prevents vectorization.
204/// Otherwise, the loop \p TheLoop is used for the location of the remark.
205void reportVectorizationFailure(const StringRef DebugMsg,
206 const StringRef OREMsg, const StringRef ORETag,
207 OptimizationRemarkEmitter *ORE, Loop *TheLoop, Instruction *I = nullptr);
208
209/// Reports an informative message: print \p Msg for debugging purposes as well
210/// as an optimization remark. Uses either \p I as location of the remark, or
211/// otherwise \p TheLoop.
212void reportVectorizationInfo(const StringRef OREMsg, const StringRef ORETag,
213 OptimizationRemarkEmitter *ORE, Loop *TheLoop,
214 Instruction *I = nullptr);
215
216} // end namespace llvm
217
218#endif // LLVM_TRANSFORMS_VECTORIZE_LOOPVECTORIZE_H
219

source code of llvm/include/llvm/Transforms/Vectorize/LoopVectorize.h