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//===- CallGraphUpdater.cpp - A (lazy) call graph update helper -----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file provides interfaces used to manipulate a call graph, regardless
/// if it is a "old style" CallGraph or an "new style" LazyCallGraph.
///
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/CallGraphUpdater.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/CallGraphSCCPass.h"
#include "llvm/IR/Constants.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
bool CallGraphUpdater::finalize() {
if (!DeadFunctionsInComdats.empty()) {
filterDeadComdatFunctions(DeadFunctionsInComdats);
DeadFunctions.append(DeadFunctionsInComdats.begin(),
DeadFunctionsInComdats.end());
}
if (CG) {
// First remove all references, e.g., outgoing via called functions. This is
// necessary as we can delete functions that have circular references.
for (Function *DeadFn : DeadFunctions) {
DeadFn->removeDeadConstantUsers();
CallGraphNode *DeadCGN = (*CG)[DeadFn];
DeadCGN->removeAllCalledFunctions();
CG->getExternalCallingNode()->removeAnyCallEdgeTo(DeadCGN);
DeadFn->replaceAllUsesWith(PoisonValue::get(DeadFn->getType()));
}
// Then remove the node and function from the module.
for (Function *DeadFn : DeadFunctions) {
CallGraphNode *DeadCGN = CG->getOrInsertFunction(DeadFn);
assert(DeadCGN->getNumReferences() == 0 &&
"References should have been handled by now");
delete CG->removeFunctionFromModule(DeadCGN);
}
} else {
// This is the code path for the new lazy call graph and for the case were
// no call graph was provided.
for (Function *DeadFn : DeadFunctions) {
DeadFn->removeDeadConstantUsers();
DeadFn->replaceAllUsesWith(PoisonValue::get(DeadFn->getType()));
if (LCG && !ReplacedFunctions.count(DeadFn)) {
// Taken mostly from the inliner:
LazyCallGraph::Node &N = LCG->get(*DeadFn);
auto *DeadSCC = LCG->lookupSCC(N);
assert(DeadSCC && DeadSCC->size() == 1 &&
&DeadSCC->begin()->getFunction() == DeadFn);
auto &DeadRC = DeadSCC->getOuterRefSCC();
FunctionAnalysisManager &FAM =
AM->getResult<FunctionAnalysisManagerCGSCCProxy>(*DeadSCC, *LCG)
.getManager();
FAM.clear(*DeadFn, DeadFn->getName());
AM->clear(*DeadSCC, DeadSCC->getName());
LCG->removeDeadFunction(*DeadFn);
// Mark the relevant parts of the call graph as invalid so we don't
// visit them.
UR->InvalidatedSCCs.insert(DeadSCC);
UR->InvalidatedRefSCCs.insert(&DeadRC);
}
// The function is now really dead and de-attached from everything.
DeadFn->eraseFromParent();
}
}
bool Changed = !DeadFunctions.empty();
DeadFunctionsInComdats.clear();
DeadFunctions.clear();
return Changed;
}
void CallGraphUpdater::reanalyzeFunction(Function &Fn) {
if (CG) {
CallGraphNode *OldCGN = CG->getOrInsertFunction(&Fn);
OldCGN->removeAllCalledFunctions();
CG->populateCallGraphNode(OldCGN);
} else if (LCG) {
LazyCallGraph::Node &N = LCG->get(Fn);
LazyCallGraph::SCC *C = LCG->lookupSCC(N);
updateCGAndAnalysisManagerForCGSCCPass(*LCG, *C, N, *AM, *UR, *FAM);
}
}
void CallGraphUpdater::registerOutlinedFunction(Function &OriginalFn,
Function &NewFn) {
if (CG)
CG->addToCallGraph(&NewFn);
else if (LCG)
LCG->addSplitFunction(OriginalFn, NewFn);
}
void CallGraphUpdater::removeFunction(Function &DeadFn) {
DeadFn.deleteBody();
DeadFn.setLinkage(GlobalValue::ExternalLinkage);
if (DeadFn.hasComdat())
DeadFunctionsInComdats.push_back(&DeadFn);
else
DeadFunctions.push_back(&DeadFn);
// For the old call graph we remove the function from the SCC right away.
if (CG && !ReplacedFunctions.count(&DeadFn)) {
CallGraphNode *DeadCGN = (*CG)[&DeadFn];
DeadCGN->removeAllCalledFunctions();
CGSCC->DeleteNode(DeadCGN);
}
if (FAM)
FAM->clear(DeadFn, DeadFn.getName());
}
void CallGraphUpdater::replaceFunctionWith(Function &OldFn, Function &NewFn) {
OldFn.removeDeadConstantUsers();
ReplacedFunctions.insert(&OldFn);
if (CG) {
// Update the call graph for the newly promoted function.
CallGraphNode *OldCGN = (*CG)[&OldFn];
CallGraphNode *NewCGN = CG->getOrInsertFunction(&NewFn);
NewCGN->stealCalledFunctionsFrom(OldCGN);
CG->ReplaceExternalCallEdge(OldCGN, NewCGN);
// And update the SCC we're iterating as well.
CGSCC->ReplaceNode(OldCGN, NewCGN);
} else if (LCG) {
// Directly substitute the functions in the call graph.
LazyCallGraph::Node &OldLCGN = LCG->get(OldFn);
SCC->getOuterRefSCC().replaceNodeFunction(OldLCGN, NewFn);
}
removeFunction(OldFn);
}
bool CallGraphUpdater::replaceCallSite(CallBase &OldCS, CallBase &NewCS) {
// This is only necessary in the (old) CG.
if (!CG)
return true;
Function *Caller = OldCS.getCaller();
CallGraphNode *NewCalleeNode =
CG->getOrInsertFunction(NewCS.getCalledFunction());
CallGraphNode *CallerNode = (*CG)[Caller];
if (llvm::none_of(*CallerNode, [&OldCS](const CallGraphNode::CallRecord &CR) {
return CR.first && *CR.first == &OldCS;
}))
return false;
CallerNode->replaceCallEdge(OldCS, NewCS, NewCalleeNode);
return true;
}
void CallGraphUpdater::removeCallSite(CallBase &CS) {
// This is only necessary in the (old) CG.
if (!CG)
return;
Function *Caller = CS.getCaller();
CallGraphNode *CallerNode = (*CG)[Caller];
CallerNode->removeCallEdgeFor(CS);
}
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