1 //===- ReduceMetadata.cpp - Specialized Delta Pass ------------------------===//
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 file implements two functions used by the Generic Delta Debugging
10 // Algorithm, which are used to reduce Metadata nodes.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "ReduceMetadata.h"
15 #include "Delta.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include <set>
18 #include <vector>
19 
20 using namespace llvm;
21 
22 /// Adds all Unnamed Metadata Nodes that are inside desired Chunks to set
23 template <class T>
24 static void getChunkMetadataNodes(T &MDUser, int &I,
25                                   const std::vector<Chunk> &ChunksToKeep,
26                                   std::set<MDNode *> &SeenNodes,
27                                   std::set<MDNode *> &NodesToKeep) {
28   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
29   MDUser.getAllMetadata(MDs);
30   for (auto &MD : MDs) {
31     SeenNodes.insert(MD.second);
32     if (I < (int)ChunksToKeep.size()) {
33       if (ChunksToKeep[I].contains(SeenNodes.size()))
34         NodesToKeep.insert(MD.second);
35       if (ChunksToKeep[I].end == (int)SeenNodes.size())
36         ++I;
37     }
38   }
39 }
40 
41 /// Erases out-of-chunk unnamed metadata nodes from its user
42 template <class T>
43 static void eraseMetadataIfOutsideChunk(T &MDUser,
44                                         const std::set<MDNode *> &NodesToKeep) {
45   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
46   MDUser.getAllMetadata(MDs);
47   for (int I = 0, E = MDs.size(); I != E; ++I)
48     if (!NodesToKeep.count(MDs[I].second))
49       MDUser.setMetadata(I, NULL);
50 }
51 
52 /// Removes all the Named and Unnamed Metadata Nodes, as well as any debug
53 /// functions that aren't inside the desired Chunks.
54 static void extractMetadataFromModule(const std::vector<Chunk> &ChunksToKeep,
55                                       Module *Program) {
56   std::set<MDNode *> SeenNodes;
57   std::set<MDNode *> NodesToKeep;
58   int I = 0;
59 
60   // Add chunk MDNodes used by GVs, Functions, and Instructions to set
61   for (auto &GV : Program->globals())
62     getChunkMetadataNodes(GV, I, ChunksToKeep, SeenNodes, NodesToKeep);
63 
64   for (auto &F : *Program) {
65     getChunkMetadataNodes(F, I, ChunksToKeep, SeenNodes, NodesToKeep);
66     for (auto &BB : F)
67       for (auto &Inst : BB)
68         getChunkMetadataNodes(Inst, I, ChunksToKeep, SeenNodes, NodesToKeep);
69   }
70 
71   // Once more, go over metadata nodes, but deleting the ones outside chunks
72   for (auto &GV : Program->globals())
73     eraseMetadataIfOutsideChunk(GV, NodesToKeep);
74 
75   for (auto &F : *Program) {
76     eraseMetadataIfOutsideChunk(F, NodesToKeep);
77     for (auto &BB : F)
78       for (auto &Inst : BB)
79         eraseMetadataIfOutsideChunk(Inst, NodesToKeep);
80   }
81 
82 
83   // Get out-of-chunk Named metadata nodes
84   unsigned MetadataCount = SeenNodes.size();
85   std::vector<NamedMDNode *> NamedNodesToDelete;
86   for (auto &MD : Program->named_metadata()) {
87     if (I < (int)ChunksToKeep.size()) {
88       if (!ChunksToKeep[I].contains(++MetadataCount))
89         NamedNodesToDelete.push_back(&MD);
90       if (ChunksToKeep[I].end == (int)SeenNodes.size())
91         ++I;
92     } else
93       NamedNodesToDelete.push_back(&MD);
94   }
95 
96   for (auto *NN : NamedNodesToDelete) {
97     for (int I = 0, E = NN->getNumOperands(); I != E; ++I)
98       NN->setOperand(I, NULL);
99     NN->eraseFromParent();
100   }
101 }
102 
103 // Gets unnamed metadata nodes used by a given instruction/GV/function and adds
104 // them to the set of seen nodes
105 template <class T>
106 static void addMetadataToSet(T &MDUser, std::set<MDNode *> &UnnamedNodes) {
107   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
108   MDUser.getAllMetadata(MDs);
109   for (auto &MD : MDs)
110     UnnamedNodes.insert(MD.second);
111 }
112 
113 /// Returns the amount of Named and Unnamed Metadata Nodes
114 static int countMetadataTargets(Module *Program) {
115   std::set<MDNode *> UnnamedNodes;
116   int NamedMetadataNodes = Program->named_metadata_size();
117 
118   // Get metadata nodes used by globals
119   for (auto &GV : Program->globals())
120     addMetadataToSet(GV, UnnamedNodes);
121 
122   // Do the same for nodes used by functions & instructions
123   for (auto &F : *Program) {
124     addMetadataToSet(F, UnnamedNodes);
125     for (auto &BB : F)
126       for (auto &I : BB)
127         addMetadataToSet(I, UnnamedNodes);
128   }
129 
130   return UnnamedNodes.size() + NamedMetadataNodes;
131 }
132 
133 void llvm::reduceMetadataDeltaPass(TestRunner &Test) {
134   outs() << "*** Reducing Metadata...\n";
135   int MDCount = countMetadataTargets(Test.getProgram());
136   runDeltaPass(Test, MDCount, extractMetadataFromModule);
137   outs() << "----------------------------\n";
138 }
139