1 //===- PruneUnprofitable.cpp ----------------------------------------------===//
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 // Mark a SCoP as unfeasible if not deemed profitable to optimize.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "polly/PruneUnprofitable.h"
14 #include "polly/ScopDetection.h"
15 #include "polly/ScopInfo.h"
16 #include "polly/ScopPass.h"
17 #include "llvm/ADT/Statistic.h"
18 #include "llvm/IR/DebugLoc.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Support/raw_ostream.h"
21 
22 using namespace llvm;
23 using namespace polly;
24 
25 #define DEBUG_TYPE "polly-prune-unprofitable"
26 
27 namespace {
28 
29 STATISTIC(ScopsProcessed,
30           "Number of SCoPs considered for unprofitability pruning");
31 STATISTIC(ScopsPruned, "Number of pruned SCoPs because it they cannot be "
32                        "optimized in a significant way");
33 STATISTIC(ScopsSurvived, "Number of SCoPs after pruning");
34 
35 STATISTIC(NumPrunedLoops, "Number of pruned loops");
36 STATISTIC(NumPrunedBoxedLoops, "Number of pruned boxed loops");
37 STATISTIC(NumPrunedAffineLoops, "Number of pruned affine loops");
38 
39 STATISTIC(NumLoopsInScop, "Number of loops in scops after pruning");
40 STATISTIC(NumBoxedLoops, "Number of boxed loops in SCoPs after pruning");
41 STATISTIC(NumAffineLoops, "Number of affine loops in SCoPs after pruning");
42 
43 class PruneUnprofitable : public ScopPass {
44 private:
45   void updateStatistics(Scop &S, bool Pruned) {
46     auto ScopStats = S.getStatistics();
47     if (Pruned) {
48       ScopsPruned++;
49       NumPrunedLoops += ScopStats.NumAffineLoops + ScopStats.NumBoxedLoops;
50       NumPrunedBoxedLoops += ScopStats.NumBoxedLoops;
51       NumPrunedAffineLoops += ScopStats.NumAffineLoops;
52     } else {
53       ScopsSurvived++;
54       NumLoopsInScop += ScopStats.NumAffineLoops + ScopStats.NumBoxedLoops;
55       NumBoxedLoops += ScopStats.NumBoxedLoops;
56       NumAffineLoops += ScopStats.NumAffineLoops;
57     }
58   }
59 
60 public:
61   static char ID;
62 
63   explicit PruneUnprofitable() : ScopPass(ID) {}
64   PruneUnprofitable(const PruneUnprofitable &) = delete;
65   PruneUnprofitable &operator=(const PruneUnprofitable &) = delete;
66 
67   void getAnalysisUsage(AnalysisUsage &AU) const override {
68     AU.addRequired<ScopInfoRegionPass>();
69     AU.setPreservesAll();
70   }
71 
72   bool runOnScop(Scop &S) override {
73     if (PollyProcessUnprofitable) {
74       LLVM_DEBUG(
75           dbgs() << "NOTE: -polly-process-unprofitable active, won't prune "
76                     "anything\n");
77       return false;
78     }
79 
80     ScopsProcessed++;
81 
82     if (!S.isProfitable(true)) {
83       LLVM_DEBUG(
84           dbgs() << "SCoP pruned because it probably cannot be optimized in "
85                     "a significant way\n");
86       S.invalidate(PROFITABLE, DebugLoc());
87       updateStatistics(S, true);
88     } else {
89       updateStatistics(S, false);
90     }
91 
92     return false;
93   }
94 };
95 } // namespace
96 
97 char PruneUnprofitable::ID;
98 
99 Pass *polly::createPruneUnprofitablePass() { return new PruneUnprofitable(); }
100 
101 INITIALIZE_PASS_BEGIN(PruneUnprofitable, "polly-prune-unprofitable",
102                       "Polly - Prune unprofitable SCoPs", false, false)
103 INITIALIZE_PASS_END(PruneUnprofitable, "polly-prune-unprofitable",
104                     "Polly - Prune unprofitable SCoPs", false, false)
105