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//===-- ExtractFunction.cpp - Function extraction pass --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass extracts
//
//===----------------------------------------------------------------------===//
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/IPO.h"
using namespace llvm;
namespace {
class FunctionExtractorPass : public ModulePass {
Function *Named;
bool deleteFunc;
public:
/// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
/// specified function. Otherwise, it deletes as much of the module as
/// possible, except for the function specified.
///
FunctionExtractorPass(Function *F = 0, bool deleteFn = true)
: Named(F), deleteFunc(deleteFn) {}
bool runOnModule(Module &M) {
if (Named == 0) {
Named = M.getMainFunction();
if (Named == 0) return false; // No function to extract
}
if (deleteFunc)
return deleteFunction();
M.setModuleInlineAsm("");
return isolateFunction(M);
}
bool deleteFunction() {
Named->setLinkage(GlobalValue::ExternalLinkage);
Named->deleteBody();
assert(Named->isExternal() && "This didn't make the function external!");
return true;
}
bool isolateFunction(Module &M) {
// Make sure our result is globally accessible...
Named->setLinkage(GlobalValue::ExternalLinkage);
// Mark all global variables internal
for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
if (!I->isExternal()) {
I->setInitializer(0); // Make all variables external
I->setLinkage(GlobalValue::ExternalLinkage);
}
// All of the functions may be used by global variables or the named
// function. Loop through them and create a new, external functions that
// can be "used", instead of ones with bodies.
std::vector<Function*> NewFunctions;
Function *Last = --M.end(); // Figure out where the last real fn is.
for (Module::iterator I = M.begin(); ; ++I) {
if (&*I != Named) {
Function *New = new Function(I->getFunctionType(),
GlobalValue::ExternalLinkage,
I->getName());
New->setCallingConv(I->getCallingConv());
I->setName(""); // Remove Old name
// If it's not the named function, delete the body of the function
I->dropAllReferences();
M.getFunctionList().push_back(New);
NewFunctions.push_back(New);
}
if (&*I == Last) break; // Stop after processing the last function
}
// Now that we have replacements all set up, loop through the module,
// deleting the old functions, replacing them with the newly created
// functions.
if (!NewFunctions.empty()) {
unsigned FuncNum = 0;
Module::iterator I = M.begin();
do {
if (&*I != Named) {
// Make everything that uses the old function use the new dummy fn
I->replaceAllUsesWith(NewFunctions[FuncNum++]);
Function *Old = I;
++I; // Move the iterator to the new function
// Delete the old function!
M.getFunctionList().erase(Old);
} else {
++I; // Skip the function we are extracting
}
} while (&*I != NewFunctions[0]);
}
return true;
}
};
RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
}
ModulePass *llvm::createFunctionExtractionPass(Function *F, bool deleteFn) {
return new FunctionExtractorPass(F, deleteFn);
}
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