ExtractGV.cpp revision 086ea05299f2a6ffc2e283c70ef4ef39897db6a3
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 if (deleteStuff) 48 return deleteGV(); 49 M.setModuleInlineAsm(""); 50 return isolateGV(M); 51 } 52 53 bool deleteGV() { 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 60 if (reLink) { 61 for (Function::iterator B = NamedFunc->begin(), BE = NamedFunc->end(); 62 B != BE; ++B) { 63 for (BasicBlock::iterator I = B->begin(), E = B->end(); 64 I != E; ++I) { 65 if (CallInst* callInst = dyn_cast<CallInst>(&*I)) { 66 Function* Callee = callInst->getCalledFunction(); 67 if (Callee && Callee->hasLocalLinkage()) 68 Callee->setLinkage(GlobalValue::ExternalLinkage); 69 } 70 } 71 } 72 } 73 74 NamedFunc->setLinkage(GlobalValue::ExternalLinkage); 75 NamedFunc->deleteBody(); 76 assert(NamedFunc->isDeclaration() && "This didn't make the function external!"); 77 } else { 78 if (!(*GI)->isDeclaration()) { 79 cast<GlobalVariable>(*GI)->setInitializer(0); //clear the initializer 80 (*GI)->setLinkage(GlobalValue::ExternalLinkage); 81 } 82 } 83 } 84 return true; 85 } 86 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); 93 } 94 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 95 if (!I->isDeclaration()) { 96 I->setLinkage(GlobalValue::InternalLinkage); 97 } 98 99 // Make sure our result is globally accessible... 100 // by putting them in the used array 101 { 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)); 108 } 109 ArrayType *AT = Context->getArrayType(SBP, AUGs.size()); 110 Constant *Init = Context->getConstantArray(AT, AUGs); 111 GlobalValue *gv = new GlobalVariable(AT, false, 112 GlobalValue::AppendingLinkage, 113 Init, "llvm.used", &M); 114 gv->setSection("llvm.metadata"); 115 } 116 117 // 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; 121 122 Function *Last = --M.end(); // Figure out where the last real fn is. 123 124 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); 129 130 // If it's not the named function, delete the body of the function 131 I->dropAllReferences(); 132 133 M.getFunctionList().push_back(New); 134 NewFunctions.push_back(New); 135 New->takeName(I); 136 } 137 138 if (&*I == Last) break; // Stop after processing the last function 139 } 140 141 // Now that we have replacements all set up, loop through the module, 142 // deleting the old functions, replacing them with the newly created 143 // functions. 144 if (!NewFunctions.empty()) { 145 unsigned FuncNum = 0; 146 Module::iterator I = M.begin(); 147 do { 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++]); 151 152 Function *Old = I; 153 ++I; // Move the iterator to the new function 154 155 // Delete the old function! 156 M.getFunctionList().erase(Old); 157 158 } else { 159 ++I; // Skip the function we are extracting 160 } 161 } while (&*I != NewFunctions[0]); 162 } 163 164 return true; 165 } 166 }; 167 168 char GVExtractorPass::ID = 0; 169} 170 171ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs, 172 bool deleteFn, bool relinkCallees) { 173 return new GVExtractorPass(GVs, deleteFn, relinkCallees); 174} 175