1 //===-- ExtractFunction.cpp - Function extraction pass --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Instructions.h"
15 #include "llvm/Module.h"
16 #include "llvm/Pass.h"
17 #include "llvm/Transforms/IPO.h"
18 #include "llvm/Support/Compiler.h"
22 /// @brief A pass to extract specific functions and their dependencies.
23 class VISIBILITY_HIDDEN FunctionExtractorPass : public ModulePass {
28 static char ID; // Pass identification, replacement for typeid
30 /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
31 /// specified function. Otherwise, it deletes as much of the module as
32 /// possible, except for the function specified.
34 explicit FunctionExtractorPass(Function *F = 0, bool deleteFn = true,
35 bool relinkCallees = false)
36 : ModulePass((intptr_t)&ID), Named(F), deleteFunc(deleteFn),
37 reLink(relinkCallees) {}
39 bool runOnModule(Module &M) {
41 Named = M.getFunction("main");
42 if (Named == 0) return false; // No function to extract
46 return deleteFunction();
47 M.setModuleInlineAsm("");
48 return isolateFunction(M);
51 bool deleteFunction() {
52 // If we're in relinking mode, set linkage of all internal callees to
53 // external. This will allow us extract function, and then - link
54 // everything together
56 for (Function::iterator B = Named->begin(), BE = Named->end();
58 for (BasicBlock::iterator I = B->begin(), E = B->end();
60 if (CallInst* callInst = dyn_cast<CallInst>(&*I)) {
61 Function* Callee = callInst->getCalledFunction();
62 if (Callee && Callee->hasInternalLinkage())
63 Callee->setLinkage(GlobalValue::ExternalLinkage);
69 Named->setLinkage(GlobalValue::ExternalLinkage);
71 assert(Named->isDeclaration() && "This didn't make the function external!");
75 bool isolateFunction(Module &M) {
76 // Make sure our result is globally accessible...
77 Named->setLinkage(GlobalValue::ExternalLinkage);
79 // Mark all global variables internal
80 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
81 if (!I->isDeclaration()) {
82 I->setInitializer(0); // Make all variables external
83 I->setLinkage(GlobalValue::ExternalLinkage);
86 // All of the functions may be used by global variables or the named
87 // function. Loop through them and create a new, external functions that
88 // can be "used", instead of ones with bodies.
89 std::vector<Function*> NewFunctions;
91 Function *Last = --M.end(); // Figure out where the last real fn is.
93 for (Module::iterator I = M.begin(); ; ++I) {
95 Function *New = new Function(I->getFunctionType(),
96 GlobalValue::ExternalLinkage);
97 New->setCallingConv(I->getCallingConv());
99 // If it's not the named function, delete the body of the function
100 I->dropAllReferences();
102 M.getFunctionList().push_back(New);
103 NewFunctions.push_back(New);
107 if (&*I == Last) break; // Stop after processing the last function
110 // Now that we have replacements all set up, loop through the module,
111 // deleting the old functions, replacing them with the newly created
113 if (!NewFunctions.empty()) {
114 unsigned FuncNum = 0;
115 Module::iterator I = M.begin();
118 // Make everything that uses the old function use the new dummy fn
119 I->replaceAllUsesWith(NewFunctions[FuncNum++]);
122 ++I; // Move the iterator to the new function
124 // Delete the old function!
125 M.getFunctionList().erase(Old);
128 ++I; // Skip the function we are extracting
130 } while (&*I != NewFunctions[0]);
137 char FunctionExtractorPass::ID = 0;
138 RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
141 ModulePass *llvm::createFunctionExtractionPass(Function *F, bool deleteFn,
142 bool relinkCallees) {
143 return new FunctionExtractorPass(F, deleteFn, relinkCallees);