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 static void updateStatistics(Scop &S, bool Pruned) {
44   Scop::ScopStatistics ScopStats = S.getStatistics();
45   if (Pruned) {
46     ScopsPruned++;
47     NumPrunedLoops += ScopStats.NumAffineLoops + ScopStats.NumBoxedLoops;
48     NumPrunedBoxedLoops += ScopStats.NumBoxedLoops;
49     NumPrunedAffineLoops += ScopStats.NumAffineLoops;
50   } else {
51     ScopsSurvived++;
52     NumLoopsInScop += ScopStats.NumAffineLoops + ScopStats.NumBoxedLoops;
53     NumBoxedLoops += ScopStats.NumBoxedLoops;
54     NumAffineLoops += ScopStats.NumAffineLoops;
55   }
56 }
57 
58 static bool runPruneUnprofitable(Scop &S) {
59   if (PollyProcessUnprofitable) {
60     LLVM_DEBUG(
61         dbgs() << "NOTE: -polly-process-unprofitable active, won't prune "
62                   "anything\n");
63     return false;
64   }
65 
66   ScopsProcessed++;
67 
68   if (!S.isProfitable(true)) {
69     LLVM_DEBUG(
70         dbgs() << "SCoP pruned because it probably cannot be optimized in "
71                   "a significant way\n");
72     S.invalidate(PROFITABLE, DebugLoc());
73     updateStatistics(S, true);
74   } else {
75     updateStatistics(S, false);
76   }
77 
78   return false;
79 }
80 
81 class PruneUnprofitableWrapperPass final : public ScopPass {
82 public:
83   static char ID;
84 
85   explicit PruneUnprofitableWrapperPass() : ScopPass(ID) {}
86   PruneUnprofitableWrapperPass(const PruneUnprofitableWrapperPass &) = delete;
87   PruneUnprofitableWrapperPass &
88   operator=(const PruneUnprofitableWrapperPass &) = delete;
89 
90   void getAnalysisUsage(AnalysisUsage &AU) const override {
91     AU.addRequired<ScopInfoRegionPass>();
92     AU.setPreservesAll();
93   }
94 
95   bool runOnScop(Scop &S) override { return runPruneUnprofitable(S); }
96 };
97 } // namespace
98 
99 char PruneUnprofitableWrapperPass::ID;
100 
101 Pass *polly::createPruneUnprofitableWrapperPass() {
102   return new PruneUnprofitableWrapperPass();
103 }
104 
105 INITIALIZE_PASS_BEGIN(PruneUnprofitableWrapperPass, "polly-prune-unprofitable",
106                       "Polly - Prune unprofitable SCoPs", false, false)
107 INITIALIZE_PASS_END(PruneUnprofitableWrapperPass, "polly-prune-unprofitable",
108                     "Polly - Prune unprofitable SCoPs", false, false)
109 
110 llvm::PreservedAnalyses
111 PruneUnprofitablePass::run(Scop &S, ScopAnalysisManager &SAM,
112                            ScopStandardAnalysisResults &SAR, SPMUpdater &U) {
113   bool Changed = runPruneUnprofitable(S);
114 
115   if (!Changed)
116     return PreservedAnalyses::all();
117 
118   PreservedAnalyses PA;
119   PA.preserveSet<AllAnalysesOn<Module>>();
120   PA.preserveSet<AllAnalysesOn<Function>>();
121   PA.preserveSet<AllAnalysesOn<Loop>>();
122   return PA;
123 }
124