LLVM API Documentation
00001 //===-- ExtractFunction.cpp - Function extraction pass --------------------===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This pass extracts 00011 // 00012 //===----------------------------------------------------------------------===// 00013 00014 #include "llvm/Module.h" 00015 #include "llvm/Pass.h" 00016 #include "llvm/Transforms/IPO.h" 00017 using namespace llvm; 00018 00019 namespace { 00020 class FunctionExtractorPass : public ModulePass { 00021 Function *Named; 00022 bool deleteFunc; 00023 public: 00024 /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the 00025 /// specified function. Otherwise, it deletes as much of the module as 00026 /// possible, except for the function specified. 00027 /// 00028 FunctionExtractorPass(Function *F = 0, bool deleteFn = true) 00029 : Named(F), deleteFunc(deleteFn) {} 00030 00031 bool runOnModule(Module &M) { 00032 if (Named == 0) { 00033 Named = M.getMainFunction(); 00034 if (Named == 0) return false; // No function to extract 00035 } 00036 00037 if (deleteFunc) 00038 return deleteFunction(); 00039 else 00040 return isolateFunction(M); 00041 } 00042 00043 bool deleteFunction() { 00044 Named->setLinkage(GlobalValue::ExternalLinkage); 00045 Named->deleteBody(); 00046 assert(Named->isExternal() && "This didn't make the function external!"); 00047 return true; 00048 } 00049 00050 bool isolateFunction(Module &M) { 00051 // Make sure our result is globally accessible... 00052 Named->setLinkage(GlobalValue::ExternalLinkage); 00053 00054 // Mark all global variables internal 00055 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I) 00056 if (!I->isExternal()) { 00057 I->setInitializer(0); // Make all variables external 00058 I->setLinkage(GlobalValue::ExternalLinkage); 00059 } 00060 00061 // All of the functions may be used by global variables or the named 00062 // function. Loop through them and create a new, external functions that 00063 // can be "used", instead of ones with bodies. 00064 std::vector<Function*> NewFunctions; 00065 00066 Function *Last = &M.back(); // Figure out where the last real fn is... 00067 00068 for (Module::iterator I = M.begin(); ; ++I) { 00069 if (&*I != Named) { 00070 Function *New = new Function(I->getFunctionType(), 00071 GlobalValue::ExternalLinkage, 00072 I->getName()); 00073 I->setName(""); // Remove Old name 00074 00075 // If it's not the named function, delete the body of the function 00076 I->dropAllReferences(); 00077 00078 M.getFunctionList().push_back(New); 00079 NewFunctions.push_back(New); 00080 } 00081 00082 if (&*I == Last) break; // Stop after processing the last function 00083 } 00084 00085 // Now that we have replacements all set up, loop through the module, 00086 // deleting the old functions, replacing them with the newly created 00087 // functions. 00088 if (!NewFunctions.empty()) { 00089 unsigned FuncNum = 0; 00090 Module::iterator I = M.begin(); 00091 do { 00092 if (&*I != Named) { 00093 // Make everything that uses the old function use the new dummy fn 00094 I->replaceAllUsesWith(NewFunctions[FuncNum++]); 00095 00096 Function *Old = I; 00097 ++I; // Move the iterator to the new function 00098 00099 // Delete the old function! 00100 M.getFunctionList().erase(Old); 00101 00102 } else { 00103 ++I; // Skip the function we are extracting 00104 } 00105 } while (&*I != NewFunctions[0]); 00106 } 00107 00108 return true; 00109 } 00110 }; 00111 00112 RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor"); 00113 } 00114 00115 ModulePass *llvm::createFunctionExtractionPass(Function *F, bool deleteFn) { 00116 return new FunctionExtractorPass(F, deleteFn); 00117 }