1 //===-- ExtractGV.cpp - Global Value extraction pass ----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass extracts global values
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Instructions.h"
15 #include "llvm/LLVMContext.h"
16 #include "llvm/Module.h"
17 #include "llvm/Pass.h"
18 #include "llvm/Constants.h"
19 #include "llvm/Transforms/IPO.h"
20 #include "llvm/Support/Compiler.h"
25 /// @brief A pass to extract specific functions and their dependencies.
26 class VISIBILITY_HIDDEN GVExtractorPass : public ModulePass {
27 std::vector<GlobalValue*> Named;
31 static char ID; // Pass identification, replacement for typeid
33 /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
34 /// specified function. Otherwise, it deletes as much of the module as
35 /// possible, except for the function specified.
37 explicit GVExtractorPass(std::vector<GlobalValue*>& GVs, bool deleteS = true,
38 bool relinkCallees = false)
39 : ModulePass(&ID), Named(GVs), deleteStuff(deleteS),
40 reLink(relinkCallees) {}
42 bool runOnModule(Module &M) {
43 if (Named.size() == 0) {
44 return false; // Nothing to extract
49 M.setModuleInlineAsm("");
54 for (std::vector<GlobalValue*>::iterator GI = Named.begin(),
55 GE = Named.end(); GI != GE; ++GI) {
56 if (Function* NamedFunc = dyn_cast<Function>(*GI)) {
57 // If we're in relinking mode, set linkage of all internal callees to
58 // external. This will allow us extract function, and then - link
59 // everything together
61 for (Function::iterator B = NamedFunc->begin(), BE = NamedFunc->end();
63 for (BasicBlock::iterator I = B->begin(), E = B->end();
65 if (CallInst* callInst = dyn_cast<CallInst>(&*I)) {
66 Function* Callee = callInst->getCalledFunction();
67 if (Callee && Callee->hasLocalLinkage())
68 Callee->setLinkage(GlobalValue::ExternalLinkage);
74 NamedFunc->setLinkage(GlobalValue::ExternalLinkage);
75 NamedFunc->deleteBody();
76 assert(NamedFunc->isDeclaration() && "This didn't make the function external!");
78 if (!(*GI)->isDeclaration()) {
79 cast<GlobalVariable>(*GI)->setInitializer(0); //clear the initializer
80 (*GI)->setLinkage(GlobalValue::ExternalLinkage);
87 bool isolateGV(Module &M) {
88 // Mark all globals internal
89 // FIXME: what should we do with private linkage?
90 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
91 if (!I->isDeclaration()) {
92 I->setLinkage(GlobalValue::InternalLinkage);
94 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
95 if (!I->isDeclaration()) {
96 I->setLinkage(GlobalValue::InternalLinkage);
99 // Make sure our result is globally accessible...
100 // by putting them in the used array
102 std::vector<Constant *> AUGs;
103 const Type *SBP= Context->getPointerTypeUnqual(Type::Int8Ty);
104 for (std::vector<GlobalValue*>::iterator GI = Named.begin(),
105 GE = Named.end(); GI != GE; ++GI) {
106 (*GI)->setLinkage(GlobalValue::ExternalLinkage);
107 AUGs.push_back(Context->getConstantExprBitCast(*GI, SBP));
109 ArrayType *AT = Context->getArrayType(SBP, AUGs.size());
110 Constant *Init = Context->getConstantArray(AT, AUGs);
111 GlobalValue *gv = new GlobalVariable(M.getContext(), AT, false,
112 GlobalValue::AppendingLinkage,
113 Init, "llvm.used", &M);
114 gv->setSection("llvm.metadata");
117 // All of the functions may be used by global variables or the named
118 // globals. Loop through them and create a new, external functions that
119 // can be "used", instead of ones with bodies.
120 std::vector<Function*> NewFunctions;
122 Function *Last = --M.end(); // Figure out where the last real fn is.
124 for (Module::iterator I = M.begin(); ; ++I) {
125 if (std::find(Named.begin(), Named.end(), &*I) == Named.end()) {
126 Function *New = Function::Create(I->getFunctionType(),
127 GlobalValue::ExternalLinkage);
128 New->copyAttributesFrom(I);
130 // If it's not the named function, delete the body of the function
131 I->dropAllReferences();
133 M.getFunctionList().push_back(New);
134 NewFunctions.push_back(New);
138 if (&*I == Last) break; // Stop after processing the last function
141 // Now that we have replacements all set up, loop through the module,
142 // deleting the old functions, replacing them with the newly created
144 if (!NewFunctions.empty()) {
145 unsigned FuncNum = 0;
146 Module::iterator I = M.begin();
148 if (std::find(Named.begin(), Named.end(), &*I) == Named.end()) {
149 // Make everything that uses the old function use the new dummy fn
150 I->replaceAllUsesWith(NewFunctions[FuncNum++]);
153 ++I; // Move the iterator to the new function
155 // Delete the old function!
156 M.getFunctionList().erase(Old);
159 ++I; // Skip the function we are extracting
161 } while (&*I != NewFunctions[0]);
168 char GVExtractorPass::ID = 0;
171 ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs,
172 bool deleteFn, bool relinkCallees) {
173 return new GVExtractorPass(GVs, deleteFn, relinkCallees);