/// scanForInterest - This function decides which arguments would be worth
/// specializing on.
void PartSpec::scanForInterest(Function& F, InterestingArgVector& args) {
for(Function::arg_iterator ii = F.arg_begin(), ee = F.arg_end();
ii != ee; ++ii) {
for(Value::use_iterator ui = ii->use_begin(), ue = ii->use_end();
ui != ue; ++ui) {
bool interesting = false;
User *U = *ui;
if (isa<CmpInst>(U)) interesting = true;
else if (isa<CallInst>(U))
interesting = ui->getOperand(0) == ii;
else if (isa<InvokeInst>(U))
interesting = ui->getOperand(0) == ii;
else if (isa<SwitchInst>(U)) interesting = true;
else if (isa<BranchInst>(U)) interesting = true;
if (interesting) {
args.push_back(std::distance(F.arg_begin(), ii));
break;
}
}
}
}
//
// Method: runOnModule()
//
// Description:
// Entry point for this LLVM pass. Search for functions which could be called
// indirectly and create clones for them which are only called by direct
// calls.
//
// Inputs:
// M - A reference to the LLVM module to transform.
//
// Outputs:
// M - The transformed LLVM module.
//
// Return value:
// true - The module was modified.
// false - The module was not modified.
//
bool
IndClone::runOnModule(Module& M) {
// Set of functions to clone
std::vector<Function*> toClone;
//
// Check all of the functions in the module. If the function could be called
// by an indirect function call, add it to our worklist of functions to
// clone.
//
for (Module::iterator I = M.begin(); I != M.end(); ++I) {
// Flag whether the function should be cloned
bool pleaseCloneTheFunction = false;
//
// Only clone functions which are defined and cannot be replaced by another
// function by the linker.
//
if (!I->isDeclaration() && !I->mayBeOverridden()) {
for (Value::use_iterator ui = I->use_begin(), ue = I->use_end();
ui != ue; ++ui) {
if (!isa<CallInst>(*ui) && !isa<InvokeInst>(*ui)) {
if(!ui->use_empty())
//
// If this function is used for anything other than a direct function
// call, then we want to clone it.
//
pleaseCloneTheFunction = true;
} else {
//
// This is a call instruction, but hold up ranger! We need to make
// sure that the function isn't passed as an argument to *another*
// function. That would make the function usable in an indirect
// function call.
//
for (unsigned index = 1; index < ui->getNumOperands(); ++index) {
if (ui->getOperand(index)->stripPointerCasts() == I) {
pleaseCloneTheFunction = true;
break;
}
}
}
//
// If we've discovered that the function could be used by an indirect
// call site, schedule it for cloning.
//
if (pleaseCloneTheFunction) {
toClone.push_back(I);
break;
}
}
}
}
//
// Update the statistics on the number of functions we'll be cloning.
// We only update the statistic if we want to clone one or more functions;
// due to the magic of how statistics work, avoiding assignment prevents it
// from needlessly showing up.
//
if (toClone.size())
numCloned += toClone.size();
//
// Go through the worklist and clone each function. After cloning a
// function, change all direct calls to use the clone instead of using the
// original function.
//
for (unsigned index = 0; index < toClone.size(); ++index) {
//
// Clone the function and give it a name indicating that it is a clone to
// be used for direct function calls.
//
Function * Original = toClone[index];
Function* DirectF = CloneFunction(Original);
DirectF->setName(Original->getName() + "_DIRECT");
//
// Make the clone internal; external code can use the original function.
//
DirectF->setLinkage(GlobalValue::InternalLinkage);
//
// Link the cloned function into the set of functions belonging to the
// module.
//
Original->getParent()->getFunctionList().push_back(DirectF);
//
// Find all uses of the function that use it as a direct call. Change
// them to use the clone.
//
for (Value::use_iterator ui = Original->use_begin(),
ue = Original->use_end();
ui != ue; ) {
CallInst *CI = dyn_cast<CallInst>(*ui);
ui++;
if (CI) {
if (CI->getCalledFunction() == Original) {
++numReplaced;
CI->setCalledFunction(DirectF);
}
}
}
}
//
// Assume that we've cloned at least one function.
//
return true;
}