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 /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
29 /// specified function. Otherwise, it deletes as much of the module as
30 /// possible, except for the function specified.
32 FunctionExtractorPass(Function *F = 0, bool deleteFn = true,
33 bool relinkCallees = false)
34 : Named(F), deleteFunc(deleteFn), reLink(relinkCallees) {}
36 bool runOnModule(Module &M) {
38 Named = M.getFunction("main");
39 if (Named == 0) return false; // No function to extract
43 return deleteFunction();
44 M.setModuleInlineAsm("");
45 return isolateFunction(M);
48 bool deleteFunction() {
49 // If we're in relinking mode, set linkage of all internal callees to
50 // external. This will allow us extract function, and then - link
51 // everything together
53 for (Function::iterator B = Named->begin(), BE = Named->end();
55 for (BasicBlock::iterator I = B->begin(), E = B->end();
57 if (CallInst* callInst = dyn_cast<CallInst>(&*I)) {
58 Function* Callee = callInst->getCalledFunction();
59 if (Callee && Callee->hasInternalLinkage())
60 Callee->setLinkage(GlobalValue::ExternalLinkage);
66 Named->setLinkage(GlobalValue::ExternalLinkage);
68 assert(Named->isDeclaration() && "This didn't make the function external!");
72 bool isolateFunction(Module &M) {
73 // Make sure our result is globally accessible...
74 Named->setLinkage(GlobalValue::ExternalLinkage);
76 // Mark all global variables internal
77 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
78 if (!I->isDeclaration()) {
79 I->setInitializer(0); // Make all variables external
80 I->setLinkage(GlobalValue::ExternalLinkage);
83 // All of the functions may be used by global variables or the named
84 // function. Loop through them and create a new, external functions that
85 // can be "used", instead of ones with bodies.
86 std::vector<Function*> NewFunctions;
88 Function *Last = --M.end(); // Figure out where the last real fn is.
90 for (Module::iterator I = M.begin(); ; ++I) {
92 Function *New = new Function(I->getFunctionType(),
93 GlobalValue::ExternalLinkage);
94 New->setCallingConv(I->getCallingConv());
96 // If it's not the named function, delete the body of the function
97 I->dropAllReferences();
99 M.getFunctionList().push_back(New);
100 NewFunctions.push_back(New);
104 if (&*I == Last) break; // Stop after processing the last function
107 // Now that we have replacements all set up, loop through the module,
108 // deleting the old functions, replacing them with the newly created
110 if (!NewFunctions.empty()) {
111 unsigned FuncNum = 0;
112 Module::iterator I = M.begin();
115 // Make everything that uses the old function use the new dummy fn
116 I->replaceAllUsesWith(NewFunctions[FuncNum++]);
119 ++I; // Move the iterator to the new function
121 // Delete the old function!
122 M.getFunctionList().erase(Old);
125 ++I; // Skip the function we are extracting
127 } while (&*I != NewFunctions[0]);
134 RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
137 ModulePass *llvm::createFunctionExtractionPass(Function *F, bool deleteFn,
138 bool relinkCallees) {
139 return new FunctionExtractorPass(F, deleteFn, relinkCallees);