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comparison lib/Transforms/IPO/Internalize.cpp @ 0:95c75e76d11b LLVM3.4

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LLVM 3.4
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 13:56:28 +0900
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children e4204d083e25
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-1:000000000000 0:95c75e76d11b
1 //===-- Internalize.cpp - Mark functions internal -------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass loops over all of the functions and variables in the input module.
11 // If the function or variable is not in the list of external names given to
12 // the pass it is marked as internal.
13 //
14 // This transformation would not be legal in a regular compilation, but it gets
15 // extra information from the linker about what is safe.
16 //
17 // For example: Internalizing a function with external linkage. Only if we are
18 // told it is only used from within this module, it is safe to do it.
19 //
20 //===----------------------------------------------------------------------===//
21
22 #define DEBUG_TYPE "internalize"
23 #include "llvm/Transforms/IPO.h"
24 #include "llvm/ADT/SmallPtrSet.h"
25 #include "llvm/ADT/Statistic.h"
26 #include "llvm/Analysis/CallGraph.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/Pass.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/Transforms/Utils/GlobalStatus.h"
33 #include "llvm/Transforms/Utils/ModuleUtils.h"
34 #include <fstream>
35 #include <set>
36 using namespace llvm;
37
38 STATISTIC(NumAliases , "Number of aliases internalized");
39 STATISTIC(NumFunctions, "Number of functions internalized");
40 STATISTIC(NumGlobals , "Number of global vars internalized");
41
42 // APIFile - A file which contains a list of symbols that should not be marked
43 // external.
44 static cl::opt<std::string>
45 APIFile("internalize-public-api-file", cl::value_desc("filename"),
46 cl::desc("A file containing list of symbol names to preserve"));
47
48 // APIList - A list of symbols that should not be marked internal.
49 static cl::list<std::string>
50 APIList("internalize-public-api-list", cl::value_desc("list"),
51 cl::desc("A list of symbol names to preserve"),
52 cl::CommaSeparated);
53
54 namespace {
55 class InternalizePass : public ModulePass {
56 std::set<std::string> ExternalNames;
57 public:
58 static char ID; // Pass identification, replacement for typeid
59 explicit InternalizePass();
60 explicit InternalizePass(ArrayRef<const char *> ExportList);
61 void LoadFile(const char *Filename);
62 virtual bool runOnModule(Module &M);
63
64 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
65 AU.setPreservesCFG();
66 AU.addPreserved<CallGraph>();
67 }
68 };
69 } // end anonymous namespace
70
71 char InternalizePass::ID = 0;
72 INITIALIZE_PASS(InternalizePass, "internalize",
73 "Internalize Global Symbols", false, false)
74
75 InternalizePass::InternalizePass()
76 : ModulePass(ID) {
77 initializeInternalizePassPass(*PassRegistry::getPassRegistry());
78 if (!APIFile.empty()) // If a filename is specified, use it.
79 LoadFile(APIFile.c_str());
80 ExternalNames.insert(APIList.begin(), APIList.end());
81 }
82
83 InternalizePass::InternalizePass(ArrayRef<const char *> ExportList)
84 : ModulePass(ID){
85 initializeInternalizePassPass(*PassRegistry::getPassRegistry());
86 for(ArrayRef<const char *>::const_iterator itr = ExportList.begin();
87 itr != ExportList.end(); itr++) {
88 ExternalNames.insert(*itr);
89 }
90 }
91
92 void InternalizePass::LoadFile(const char *Filename) {
93 // Load the APIFile...
94 std::ifstream In(Filename);
95 if (!In.good()) {
96 errs() << "WARNING: Internalize couldn't load file '" << Filename
97 << "'! Continuing as if it's empty.\n";
98 return; // Just continue as if the file were empty
99 }
100 while (In) {
101 std::string Symbol;
102 In >> Symbol;
103 if (!Symbol.empty())
104 ExternalNames.insert(Symbol);
105 }
106 }
107
108 static bool shouldInternalize(const GlobalValue &GV,
109 const std::set<std::string> &ExternalNames) {
110 // Function must be defined here
111 if (GV.isDeclaration())
112 return false;
113
114 // Available externally is really just a "declaration with a body".
115 if (GV.hasAvailableExternallyLinkage())
116 return false;
117
118 // Already has internal linkage
119 if (GV.hasLocalLinkage())
120 return false;
121
122 // Marked to keep external?
123 if (ExternalNames.count(GV.getName()))
124 return false;
125
126 return true;
127 }
128
129 bool InternalizePass::runOnModule(Module &M) {
130 CallGraph *CG = getAnalysisIfAvailable<CallGraph>();
131 CallGraphNode *ExternalNode = CG ? CG->getExternalCallingNode() : 0;
132 bool Changed = false;
133
134 SmallPtrSet<GlobalValue *, 8> Used;
135 collectUsedGlobalVariables(M, Used, false);
136
137 // We must assume that globals in llvm.used have a reference that not even
138 // the linker can see, so we don't internalize them.
139 // For llvm.compiler.used the situation is a bit fuzzy. The assembler and
140 // linker can drop those symbols. If this pass is running as part of LTO,
141 // one might think that it could just drop llvm.compiler.used. The problem
142 // is that even in LTO llvm doesn't see every reference. For example,
143 // we don't see references from function local inline assembly. To be
144 // conservative, we internalize symbols in llvm.compiler.used, but we
145 // keep llvm.compiler.used so that the symbol is not deleted by llvm.
146 for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.begin(), E = Used.end();
147 I != E; ++I) {
148 GlobalValue *V = *I;
149 ExternalNames.insert(V->getName());
150 }
151
152 // Mark all functions not in the api as internal.
153 // FIXME: maybe use private linkage?
154 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
155 if (!shouldInternalize(*I, ExternalNames))
156 continue;
157
158 I->setLinkage(GlobalValue::InternalLinkage);
159
160 if (ExternalNode)
161 // Remove a callgraph edge from the external node to this function.
162 ExternalNode->removeOneAbstractEdgeTo((*CG)[I]);
163
164 Changed = true;
165 ++NumFunctions;
166 DEBUG(dbgs() << "Internalizing func " << I->getName() << "\n");
167 }
168
169 // Never internalize the llvm.used symbol. It is used to implement
170 // attribute((used)).
171 // FIXME: Shouldn't this just filter on llvm.metadata section??
172 ExternalNames.insert("llvm.used");
173 ExternalNames.insert("llvm.compiler.used");
174
175 // Never internalize anchors used by the machine module info, else the info
176 // won't find them. (see MachineModuleInfo.)
177 ExternalNames.insert("llvm.global_ctors");
178 ExternalNames.insert("llvm.global_dtors");
179 ExternalNames.insert("llvm.global.annotations");
180
181 // Never internalize symbols code-gen inserts.
182 // FIXME: We should probably add this (and the __stack_chk_guard) via some
183 // type of call-back in CodeGen.
184 ExternalNames.insert("__stack_chk_fail");
185 ExternalNames.insert("__stack_chk_guard");
186
187 // Mark all global variables with initializers that are not in the api as
188 // internal as well.
189 // FIXME: maybe use private linkage?
190 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
191 I != E; ++I) {
192 if (!shouldInternalize(*I, ExternalNames))
193 continue;
194
195 I->setLinkage(GlobalValue::InternalLinkage);
196 Changed = true;
197 ++NumGlobals;
198 DEBUG(dbgs() << "Internalized gvar " << I->getName() << "\n");
199 }
200
201 // Mark all aliases that are not in the api as internal as well.
202 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
203 I != E; ++I) {
204 if (!shouldInternalize(*I, ExternalNames))
205 continue;
206
207 I->setLinkage(GlobalValue::InternalLinkage);
208 Changed = true;
209 ++NumAliases;
210 DEBUG(dbgs() << "Internalized alias " << I->getName() << "\n");
211 }
212
213 return Changed;
214 }
215
216 ModulePass *llvm::createInternalizePass() {
217 return new InternalizePass();
218 }
219
220 ModulePass *llvm::createInternalizePass(ArrayRef<const char *> ExportList) {
221 return new InternalizePass(ExportList);
222 }