llvm-project/llvm/lib/Transforms/Utils/CallGraphUpdater.cpp
Sergey Dmitriev cb8faaacb5 [CallGraph] Add support for callback call sites
Summary:
This patch changes call graph analysis to recognize callback call sites
and add an artificial 'reference' call record from the broker function
caller to the callback function in the call graph. A presence of such
reference enforces bottom-up traversal order for callback functions in
CG SCC pass manager because callback function logically becomes a callee
of the broker function caller.

Reviewers: jdoerfert, hfinkel, sstefan1, baziotis

Reviewed By: jdoerfert

Subscribers: hiraditya, kuter, sstefan1, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D82572
2020-07-01 13:44:11 -07:00

168 lines
5.8 KiB
C++

//===- 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/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
bool CallGraphUpdater::finalize() {
if (!DeadFunctionsInComdats.empty()) {
filterDeadComdatFunctions(*DeadFunctionsInComdats.front()->getParent(),
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(UndefValue::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(UndefValue::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 &NewFn) {
if (CG)
CG->addToCallGraph(&NewFn);
else if (LCG)
LCG->addNewFunctionIntoSCC(NewFn, *SCC);
}
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);
}
}
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);
}