1 //===--------- PolyhedralInfo.cpp - Create Scops from LLVM IR-------------===//
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 // An interface to the Polyhedral analysis engine(Polly) of LLVM.
10 //
11 // This pass provides an interface to the polyhedral analysis performed by
12 // Polly.
13 //
14 // This interface provides basic interface like isParallel, isVectorizable
15 // that can be used in LLVM transformation passes.
16 //
17 // Work in progress, this file is subject to change.
18 //
19 //===----------------------------------------------------------------------===//
20
21 #include "polly/PolyhedralInfo.h"
22 #include "polly/DependenceInfo.h"
23 #include "polly/LinkAllPasses.h"
24 #include "polly/Options.h"
25 #include "polly/ScopInfo.h"
26 #include "polly/Support/GICHelper.h"
27 #include "llvm/Analysis/LoopInfo.h"
28 #include "llvm/InitializePasses.h"
29 #include "llvm/Support/Debug.h"
30 #include "isl/union_map.h"
31
32 using namespace llvm;
33 using namespace polly;
34
35 #define DEBUG_TYPE "polyhedral-info"
36
37 static cl::opt<bool> CheckParallel("polly-check-parallel",
38 cl::desc("Check for parallel loops"),
39 cl::Hidden, cl::init(false), cl::ZeroOrMore,
40 cl::cat(PollyCategory));
41
42 static cl::opt<bool> CheckVectorizable("polly-check-vectorizable",
43 cl::desc("Check for vectorizable loops"),
44 cl::Hidden, cl::init(false),
45 cl::ZeroOrMore, cl::cat(PollyCategory));
46
getAnalysisUsage(AnalysisUsage & AU) const47 void PolyhedralInfo::getAnalysisUsage(AnalysisUsage &AU) const {
48 AU.addRequiredTransitive<DependenceInfoWrapperPass>();
49 AU.addRequired<LoopInfoWrapperPass>();
50 AU.addRequiredTransitive<ScopInfoWrapperPass>();
51 AU.setPreservesAll();
52 }
53
runOnFunction(Function & F)54 bool PolyhedralInfo::runOnFunction(Function &F) {
55 DI = &getAnalysis<DependenceInfoWrapperPass>();
56 SI = getAnalysis<ScopInfoWrapperPass>().getSI();
57 return false;
58 }
59
print(raw_ostream & OS,const Module *) const60 void PolyhedralInfo::print(raw_ostream &OS, const Module *) const {
61 auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
62 for (auto *TopLevelLoop : LI) {
63 for (auto *L : depth_first(TopLevelLoop)) {
64 OS.indent(2) << L->getHeader()->getName() << ":\t";
65 if (CheckParallel && isParallel(L))
66 OS << "Loop is parallel.\n";
67 else if (CheckParallel)
68 OS << "Loop is not parallel.\n";
69 }
70 }
71 }
72
checkParallel(Loop * L,isl_pw_aff ** MinDepDistPtr) const73 bool PolyhedralInfo::checkParallel(Loop *L, isl_pw_aff **MinDepDistPtr) const {
74 bool IsParallel;
75 const Scop *S = getScopContainingLoop(L);
76 if (!S)
77 return false;
78 const Dependences &D =
79 DI->getDependences(const_cast<Scop *>(S), Dependences::AL_Access);
80 if (!D.hasValidDependences())
81 return false;
82 LLVM_DEBUG(dbgs() << "Loop :\t" << L->getHeader()->getName() << ":\n");
83
84 isl_union_map *Deps =
85 D.getDependences(Dependences::TYPE_RAW | Dependences::TYPE_WAW |
86 Dependences::TYPE_WAR | Dependences::TYPE_RED)
87 .release();
88
89 LLVM_DEBUG(dbgs() << "Dependences :\t" << stringFromIslObj(Deps, "null")
90 << "\n");
91
92 isl_union_map *Schedule = getScheduleForLoop(S, L);
93 LLVM_DEBUG(dbgs() << "Schedule: \t" << stringFromIslObj(Schedule, "null")
94 << "\n");
95
96 IsParallel = D.isParallel(Schedule, Deps, MinDepDistPtr);
97 isl_union_map_free(Schedule);
98 return IsParallel;
99 }
100
isParallel(Loop * L) const101 bool PolyhedralInfo::isParallel(Loop *L) const { return checkParallel(L); }
102
getScopContainingLoop(Loop * L) const103 const Scop *PolyhedralInfo::getScopContainingLoop(Loop *L) const {
104 assert((SI) && "ScopInfoWrapperPass is required by PolyhedralInfo pass!\n");
105 for (auto &It : *SI) {
106 Region *R = It.first;
107 if (R->contains(L))
108 return It.second.get();
109 }
110 return nullptr;
111 }
112
113 // Given a Loop and the containing SCoP, we compute the partial schedule
114 // by taking union of individual schedules of each ScopStmt within the loop
115 // and projecting out the inner dimensions from the range of the schedule.
116 // for (i = 0; i < n; i++)
117 // for (j = 0; j < n; j++)
118 // A[j] = 1; //Stmt
119 //
120 // The original schedule will be
121 // Stmt[i0, i1] -> [i0, i1]
122 // The schedule for the outer loop will be
123 // Stmt[i0, i1] -> [i0]
124 // The schedule for the inner loop will be
125 // Stmt[i0, i1] -> [i0, i1]
getScheduleForLoop(const Scop * S,Loop * L) const126 __isl_give isl_union_map *PolyhedralInfo::getScheduleForLoop(const Scop *S,
127 Loop *L) const {
128 isl_union_map *Schedule = isl_union_map_empty(S->getParamSpace().release());
129 int CurrDim = S->getRelativeLoopDepth(L);
130 LLVM_DEBUG(dbgs() << "Relative loop depth:\t" << CurrDim << "\n");
131 assert(CurrDim >= 0 && "Loop in region should have at least depth one");
132
133 for (auto &SS : *S) {
134 if (L->contains(SS.getSurroundingLoop())) {
135
136 unsigned int MaxDim = SS.getNumIterators();
137 LLVM_DEBUG(dbgs() << "Maximum depth of Stmt:\t" << MaxDim << "\n");
138 isl_map *ScheduleMap = SS.getSchedule().release();
139 assert(
140 ScheduleMap &&
141 "Schedules that contain extension nodes require special handling.");
142
143 ScheduleMap = isl_map_project_out(ScheduleMap, isl_dim_out, CurrDim + 1,
144 MaxDim - CurrDim - 1);
145 ScheduleMap = isl_map_set_tuple_id(ScheduleMap, isl_dim_in,
146 SS.getDomainId().release());
147 Schedule =
148 isl_union_map_union(Schedule, isl_union_map_from_map(ScheduleMap));
149 }
150 }
151 Schedule = isl_union_map_coalesce(Schedule);
152 return Schedule;
153 }
154
155 char PolyhedralInfo::ID = 0;
156
createPolyhedralInfoPass()157 Pass *polly::createPolyhedralInfoPass() { return new PolyhedralInfo(); }
158
159 INITIALIZE_PASS_BEGIN(PolyhedralInfo, "polyhedral-info",
160 "Polly - Interface to polyhedral analysis engine", false,
161 false);
162 INITIALIZE_PASS_DEPENDENCY(DependenceInfoWrapperPass);
163 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
164 INITIALIZE_PASS_DEPENDENCY(ScopInfoWrapperPass);
165 INITIALIZE_PASS_END(PolyhedralInfo, "polyhedral-info",
166 "Polly - Interface to polyhedral analysis engine", false,
167 false)
168