llvm-6502/lib/Transforms/IPO/ExtractFunction.cpp

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//===-- ExtractFunction.cpp - Function extraction pass --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass extracts
//
//===----------------------------------------------------------------------===//
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Support/Compiler.h"
using namespace llvm;
namespace {
/// @brief A pass to extract specific functions and their dependencies.
class VISIBILITY_HIDDEN FunctionExtractorPass : public ModulePass {
Function *Named;
bool deleteFunc;
bool reLink;
public:
static char ID; // Pass identification, replacement for typeid
/// 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.
///
explicit FunctionExtractorPass(Function *F = 0, bool deleteFn = true,
bool relinkCallees = false)
: ModulePass((intptr_t)&ID), Named(F), deleteFunc(deleteFn),
reLink(relinkCallees) {}
bool runOnModule(Module &M) {
if (Named == 0) {
Named = M.getFunction("main");
if (Named == 0) return false; // No function to extract
}
if (deleteFunc)
return deleteFunction();
M.setModuleInlineAsm("");
return isolateFunction(M);
}
bool deleteFunction() {
// If we're in relinking mode, set linkage of all internal callees to
// external. This will allow us extract function, and then - link
// everything together
if (reLink) {
for (Function::iterator B = Named->begin(), BE = Named->end();
B != BE; ++B) {
for (BasicBlock::iterator I = B->begin(), E = B->end();
I != E; ++I) {
if (CallInst* callInst = dyn_cast<CallInst>(&*I)) {
Function* Callee = callInst->getCalledFunction();
if (Callee && Callee->hasInternalLinkage())
Callee->setLinkage(GlobalValue::ExternalLinkage);
}
}
}
}
Named->setLinkage(GlobalValue::ExternalLinkage);
Named->deleteBody();
assert(Named->isDeclaration() && "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->isDeclaration()) {
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);
New->setCallingConv(I->getCallingConv());
New->setParamAttrs(I->getParamAttrs());
if (I->hasCollector())
New->setCollector(I->getCollector());
// If it's not the named function, delete the body of the function
I->dropAllReferences();
M.getFunctionList().push_back(New);
NewFunctions.push_back(New);
New->takeName(I);
}
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;
}
};
char FunctionExtractorPass::ID = 0;
RegisterPass<FunctionExtractorPass> X("extract", "Function Extractor");
}
ModulePass *llvm::createFunctionExtractionPass(Function *F, bool deleteFn,
bool relinkCallees) {
return new FunctionExtractorPass(F, deleteFn, relinkCallees);
}