ExtractGV.cpp revision 198090
1//===-- ExtractGV.cpp - Global Value extraction pass ----------------------===// 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 extracts global values 11// 12//===----------------------------------------------------------------------===// 13 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" 21#include <algorithm> 22using namespace llvm; 23 24namespace { 25 /// @brief A pass to extract specific functions and their dependencies. 26 class VISIBILITY_HIDDEN GVExtractorPass : public ModulePass { 27 std::vector<GlobalValue*> Named; 28 bool deleteStuff; 29 bool reLink; 30 public: 31 static char ID; // Pass identification, replacement for typeid 32 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. 36 /// 37 explicit GVExtractorPass(std::vector<GlobalValue*>& GVs, bool deleteS = true, 38 bool relinkCallees = false) 39 : ModulePass(&ID), Named(GVs), deleteStuff(deleteS), 40 reLink(relinkCallees) {} 41 42 bool runOnModule(Module &M) { 43 if (Named.size() == 0) { 44 return false; // Nothing to extract 45 } 46 47 48 if (deleteStuff) 49 return deleteGV(); 50 M.setModuleInlineAsm(""); 51 return isolateGV(M); 52 } 53 54 bool deleteGV() { 55 for (std::vector<GlobalValue*>::iterator GI = Named.begin(), 56 GE = Named.end(); GI != GE; ++GI) { 57 if (Function* NamedFunc = dyn_cast<Function>(*GI)) { 58 // If we're in relinking mode, set linkage of all internal callees to 59 // external. This will allow us extract function, and then - link 60 // everything together 61 if (reLink) { 62 for (Function::iterator B = NamedFunc->begin(), BE = NamedFunc->end(); 63 B != BE; ++B) { 64 for (BasicBlock::iterator I = B->begin(), E = B->end(); 65 I != E; ++I) { 66 if (CallInst* callInst = dyn_cast<CallInst>(&*I)) { 67 Function* Callee = callInst->getCalledFunction(); 68 if (Callee && Callee->hasLocalLinkage()) 69 Callee->setLinkage(GlobalValue::ExternalLinkage); 70 } 71 } 72 } 73 } 74 75 NamedFunc->setLinkage(GlobalValue::ExternalLinkage); 76 NamedFunc->deleteBody(); 77 assert(NamedFunc->isDeclaration() && "This didn't make the function external!"); 78 } else { 79 if (!(*GI)->isDeclaration()) { 80 cast<GlobalVariable>(*GI)->setInitializer(0); //clear the initializer 81 (*GI)->setLinkage(GlobalValue::ExternalLinkage); 82 } 83 } 84 } 85 return true; 86 } 87 88 bool isolateGV(Module &M) { 89 // Mark all globals internal 90 // FIXME: what should we do with private linkage? 91 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I) 92 if (!I->isDeclaration()) { 93 I->setLinkage(GlobalValue::InternalLinkage); 94 } 95 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 96 if (!I->isDeclaration()) { 97 I->setLinkage(GlobalValue::InternalLinkage); 98 } 99 100 // Make sure our result is globally accessible... 101 // by putting them in the used array 102 { 103 std::vector<Constant *> AUGs; 104 const Type *SBP= 105 Type::getInt8PtrTy(M.getContext()); 106 for (std::vector<GlobalValue*>::iterator GI = Named.begin(), 107 GE = Named.end(); GI != GE; ++GI) { 108 (*GI)->setLinkage(GlobalValue::ExternalLinkage); 109 AUGs.push_back(ConstantExpr::getBitCast(*GI, SBP)); 110 } 111 ArrayType *AT = ArrayType::get(SBP, AUGs.size()); 112 Constant *Init = ConstantArray::get(AT, AUGs); 113 GlobalValue *gv = new GlobalVariable(M, AT, false, 114 GlobalValue::AppendingLinkage, 115 Init, "llvm.used"); 116 gv->setSection("llvm.metadata"); 117 } 118 119 // All of the functions may be used by global variables or the named 120 // globals. Loop through them and create a new, external functions that 121 // can be "used", instead of ones with bodies. 122 std::vector<Function*> NewFunctions; 123 124 Function *Last = --M.end(); // Figure out where the last real fn is. 125 126 for (Module::iterator I = M.begin(); ; ++I) { 127 if (std::find(Named.begin(), Named.end(), &*I) == Named.end()) { 128 Function *New = Function::Create(I->getFunctionType(), 129 GlobalValue::ExternalLinkage); 130 New->copyAttributesFrom(I); 131 132 // If it's not the named function, delete the body of the function 133 I->dropAllReferences(); 134 135 M.getFunctionList().push_back(New); 136 NewFunctions.push_back(New); 137 New->takeName(I); 138 } 139 140 if (&*I == Last) break; // Stop after processing the last function 141 } 142 143 // Now that we have replacements all set up, loop through the module, 144 // deleting the old functions, replacing them with the newly created 145 // functions. 146 if (!NewFunctions.empty()) { 147 unsigned FuncNum = 0; 148 Module::iterator I = M.begin(); 149 do { 150 if (std::find(Named.begin(), Named.end(), &*I) == Named.end()) { 151 // Make everything that uses the old function use the new dummy fn 152 I->replaceAllUsesWith(NewFunctions[FuncNum++]); 153 154 Function *Old = I; 155 ++I; // Move the iterator to the new function 156 157 // Delete the old function! 158 M.getFunctionList().erase(Old); 159 160 } else { 161 ++I; // Skip the function we are extracting 162 } 163 } while (&*I != NewFunctions[0]); 164 } 165 166 return true; 167 } 168 }; 169 170 char GVExtractorPass::ID = 0; 171} 172 173ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs, 174 bool deleteFn, bool relinkCallees) { 175 return new GVExtractorPass(GVs, deleteFn, relinkCallees); 176} 177