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//===-- ExtractGV.cpp - Global Value 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 global values
//
//===----------------------------------------------------------------------===//
#include "llvm/Instructions.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Constants.h"
#include "llvm/Transforms/IPO.h"
#include <algorithm>
using namespace llvm;
namespace {
/// @brief A pass to extract specific functions and their dependencies.
class GVExtractorPass : public ModulePass {
std::vector<GlobalValue*> Named;
bool deleteStuff;
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 GVExtractorPass(std::vector<GlobalValue*>& GVs, bool deleteS = true,
bool relinkCallees = false)
: ModulePass(ID), Named(GVs), deleteStuff(deleteS),
reLink(relinkCallees) {}
bool runOnModule(Module &M) {
if (Named.size() == 0) {
return false; // Nothing to extract
}
if (deleteStuff)
return deleteGV();
M.setModuleInlineAsm("");
return isolateGV(M);
}
bool deleteGV() {
for (std::vector<GlobalValue*>::iterator GI = Named.begin(),
GE = Named.end(); GI != GE; ++GI) {
if (Function* NamedFunc = dyn_cast<Function>(*GI)) {
// 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 = NamedFunc->begin(), BE = NamedFunc->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->hasLocalLinkage())
Callee->setLinkage(GlobalValue::ExternalLinkage);
}
}
}
}
NamedFunc->setLinkage(GlobalValue::ExternalLinkage);
NamedFunc->deleteBody();
assert(NamedFunc->isDeclaration() && "This didn't make the function external!");
} else {
if (!(*GI)->isDeclaration()) {
cast<GlobalVariable>(*GI)->setInitializer(0); //clear the initializer
(*GI)->setLinkage(GlobalValue::ExternalLinkage);
}
}
}
return true;
}
bool isolateGV(Module &M) {
// Mark all globals internal
// FIXME: what should we do with private linkage?
for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
if (!I->isDeclaration()) {
I->setLinkage(GlobalValue::InternalLinkage);
}
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
if (!I->isDeclaration()) {
I->setLinkage(GlobalValue::InternalLinkage);
}
// Make sure our result is globally accessible...
// by putting them in the used array
{
std::vector<Constant *> AUGs;
const Type *SBP=
Type::getInt8PtrTy(M.getContext());
for (std::vector<GlobalValue*>::iterator GI = Named.begin(),
GE = Named.end(); GI != GE; ++GI) {
(*GI)->setLinkage(GlobalValue::ExternalLinkage);
AUGs.push_back(ConstantExpr::getBitCast(*GI, SBP));
}
ArrayType *AT = ArrayType::get(SBP, AUGs.size());
Constant *Init = ConstantArray::get(AT, AUGs);
GlobalValue *gv = new GlobalVariable(M, AT, false,
GlobalValue::AppendingLinkage,
Init, "llvm.used");
gv->setSection("llvm.metadata");
}
// All of the functions may be used by global variables or the named
// globals. 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 (std::find(Named.begin(), Named.end(), &*I) == Named.end()) {
Function *New = Function::Create(I->getFunctionType(),
GlobalValue::ExternalLinkage);
New->copyAttributesFrom(I);
// 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 (std::find(Named.begin(), Named.end(), &*I) == Named.end()) {
// 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 GVExtractorPass::ID = 0;
}
ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs,
bool deleteFn, bool relinkCallees) {
return new GVExtractorPass(GVs, deleteFn, relinkCallees);
}
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