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llvm/lib/Analysis/IPA/CallGraphSCCPass.cpp
Chandler Carruth 54fec07ec0 [PM] Split the CallGraph out from the ModulePass which creates the 
CallGraph.

This makes the CallGraph a totally generic analysis object that is the
container for the graph data structure and the primary interface for
querying and manipulating it. The pass logic is separated into its own
class. For compatibility reasons, the pass provides wrapper methods for
most of the methods on CallGraph -- they all just forward.

This will allow the new pass manager infrastructure to provide its own
analysis pass that constructs the same CallGraph object and makes it
available. The idea is that in the new pass manager, the analysis pass's
'run' method returns a concrete analysis 'result'. Here, that result is
a 'CallGraph'. The 'run' method will typically do only minimal work,
deferring much of the work into the implementation of the result object
in order to be lazy about computing things, but when (like DomTree)
there is *some* up-front computation, the analysis does it prior to
handing the result back to the querying pass.

I know some of this is fairly ugly. I'm happy to change it around if
folks can suggest a cleaner interim state, but there is going to be some
amount of unavoidable ugliness during the transition period. The good
thing is that this is very limited and will naturally go away when the
old pass infrastructure goes away. It won't hang around to bother us
later.

Next up is the initial new-PM-style call graph analysis. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195722 91177308-0d34-0410-b5e6-96231b3b80d8
2013-11-26 04:19:30 +00:00

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//===- CallGraphSCCPass.cpp - Pass that operates BU on call graph ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the CallGraphSCCPass class, which is used for passes
// which are implemented as bottom-up traversals on the call graph. Because
// there may be cycles in the call graph, passes of this type operate on the
// call-graph in SCC order: that is, they process function bottom-up, except for
// recursive functions, which they process all at once.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "cgscc-passmgr"
#include "llvm/Analysis/CallGraphSCCPass.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LegacyPassManagers.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
static cl::opt<unsigned>
MaxIterations("max-cg-scc-iterations", cl::ReallyHidden, cl::init(4));
STATISTIC(MaxSCCIterations, "Maximum CGSCCPassMgr iterations on one SCC");
//===----------------------------------------------------------------------===//
// CGPassManager
//
/// CGPassManager manages FPPassManagers and CallGraphSCCPasses.
namespace {
class CGPassManager : public ModulePass, public PMDataManager {
public:
static char ID;
explicit CGPassManager()
: ModulePass(ID), PMDataManager() { }
/// run - Execute all of the passes scheduled for execution. Keep track of
/// whether any of the passes modifies the module, and if so, return true.
bool runOnModule(Module &M);
using ModulePass::doInitialization;
using ModulePass::doFinalization;
bool doInitialization(CallGraph &CG);
bool doFinalization(CallGraph &CG);
/// Pass Manager itself does not invalidate any analysis info.
void getAnalysisUsage(AnalysisUsage &Info) const {
// CGPassManager walks SCC and it needs CallGraph.
Info.addRequired<CallGraphWrapperPass>();
Info.setPreservesAll();
}
virtual const char *getPassName() const {
return "CallGraph Pass Manager";
}
virtual PMDataManager *getAsPMDataManager() { return this; }
virtual Pass *getAsPass() { return this; }
// Print passes managed by this manager
void dumpPassStructure(unsigned Offset) {
errs().indent(Offset*2) << "Call Graph SCC Pass Manager\n";
for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
Pass *P = getContainedPass(Index);
P->dumpPassStructure(Offset + 1);
dumpLastUses(P, Offset+1);
}
}
Pass *getContainedPass(unsigned N) {
assert(N < PassVector.size() && "Pass number out of range!");
return static_cast<Pass *>(PassVector[N]);
}
virtual PassManagerType getPassManagerType() const {
return PMT_CallGraphPassManager;
}
private:
bool RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
bool &DevirtualizedCall);
bool RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
CallGraph &CG, bool &CallGraphUpToDate,
bool &DevirtualizedCall);
bool RefreshCallGraph(CallGraphSCC &CurSCC, CallGraph &CG,
bool IsCheckingMode);
};
} // end anonymous namespace.
char CGPassManager::ID = 0;
bool CGPassManager::RunPassOnSCC(Pass *P, CallGraphSCC &CurSCC,
CallGraph &CG, bool &CallGraphUpToDate,
bool &DevirtualizedCall) {
bool Changed = false;
PMDataManager *PM = P->getAsPMDataManager();
if (PM == 0) {
CallGraphSCCPass *CGSP = (CallGraphSCCPass*)P;
if (!CallGraphUpToDate) {
DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
CallGraphUpToDate = true;
}
{
TimeRegion PassTimer(getPassTimer(CGSP));
Changed = CGSP->runOnSCC(CurSCC);
}
// After the CGSCCPass is done, when assertions are enabled, use
// RefreshCallGraph to verify that the callgraph was correctly updated.
#ifndef NDEBUG
if (Changed)
RefreshCallGraph(CurSCC, CG, true);
#endif
return Changed;
}
assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
"Invalid CGPassManager member");
FPPassManager *FPP = (FPPassManager*)P;
// Run pass P on all functions in the current SCC.
for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
I != E; ++I) {
if (Function *F = (*I)->getFunction()) {
dumpPassInfo(P, EXECUTION_MSG, ON_FUNCTION_MSG, F->getName());
TimeRegion PassTimer(getPassTimer(FPP));
Changed |= FPP->runOnFunction(*F);
}
}
// The function pass(es) modified the IR, they may have clobbered the
// callgraph.
if (Changed && CallGraphUpToDate) {
DEBUG(dbgs() << "CGSCCPASSMGR: Pass Dirtied SCC: "
<< P->getPassName() << '\n');
CallGraphUpToDate = false;
}
return Changed;
}
/// RefreshCallGraph - Scan the functions in the specified CFG and resync the
/// callgraph with the call sites found in it. This is used after
/// FunctionPasses have potentially munged the callgraph, and can be used after
/// CallGraphSCC passes to verify that they correctly updated the callgraph.
///
/// This function returns true if it devirtualized an existing function call,
/// meaning it turned an indirect call into a direct call. This happens when
/// a function pass like GVN optimizes away stuff feeding the indirect call.
/// This never happens in checking mode.
///
bool CGPassManager::RefreshCallGraph(CallGraphSCC &CurSCC,
CallGraph &CG, bool CheckingMode) {
DenseMap<Value*, CallGraphNode*> CallSites;
DEBUG(dbgs() << "CGSCCPASSMGR: Refreshing SCC with " << CurSCC.size()
<< " nodes:\n";
for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
I != E; ++I)
(*I)->dump();
);
bool MadeChange = false;
bool DevirtualizedCall = false;
// Scan all functions in the SCC.
unsigned FunctionNo = 0;
for (CallGraphSCC::iterator SCCIdx = CurSCC.begin(), E = CurSCC.end();
SCCIdx != E; ++SCCIdx, ++FunctionNo) {
CallGraphNode *CGN = *SCCIdx;
Function *F = CGN->getFunction();
if (F == 0 || F->isDeclaration()) continue;
// Walk the function body looking for call sites. Sync up the call sites in
// CGN with those actually in the function.
// Keep track of the number of direct and indirect calls that were
// invalidated and removed.
unsigned NumDirectRemoved = 0, NumIndirectRemoved = 0;
// Get the set of call sites currently in the function.
for (CallGraphNode::iterator I = CGN->begin(), E = CGN->end(); I != E; ) {
// If this call site is null, then the function pass deleted the call
// entirely and the WeakVH nulled it out.
if (I->first == 0 ||
// If we've already seen this call site, then the FunctionPass RAUW'd
// one call with another, which resulted in two "uses" in the edge
// list of the same call.
CallSites.count(I->first) ||
// If the call edge is not from a call or invoke, then the function
// pass RAUW'd a call with another value. This can happen when
// constant folding happens of well known functions etc.
!CallSite(I->first)) {
assert(!CheckingMode &&
"CallGraphSCCPass did not update the CallGraph correctly!");
// If this was an indirect call site, count it.
if (I->second->getFunction() == 0)
++NumIndirectRemoved;
else
++NumDirectRemoved;
// Just remove the edge from the set of callees, keep track of whether
// I points to the last element of the vector.
bool WasLast = I + 1 == E;
CGN->removeCallEdge(I);
// If I pointed to the last element of the vector, we have to bail out:
// iterator checking rejects comparisons of the resultant pointer with
// end.
if (WasLast)
break;
E = CGN->end();
continue;
}
assert(!CallSites.count(I->first) &&
"Call site occurs in node multiple times");
CallSites.insert(std::make_pair(I->first, I->second));
++I;
}
// Loop over all of the instructions in the function, getting the callsites.
// Keep track of the number of direct/indirect calls added.
unsigned NumDirectAdded = 0, NumIndirectAdded = 0;
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
CallSite CS(cast<Value>(I));
if (!CS) continue;
Function *Callee = CS.getCalledFunction();
if (Callee && Callee->isIntrinsic()) continue;
// If this call site already existed in the callgraph, just verify it
// matches up to expectations and remove it from CallSites.
DenseMap<Value*, CallGraphNode*>::iterator ExistingIt =
CallSites.find(CS.getInstruction());
if (ExistingIt != CallSites.end()) {
CallGraphNode *ExistingNode = ExistingIt->second;
// Remove from CallSites since we have now seen it.
CallSites.erase(ExistingIt);
// Verify that the callee is right.
if (ExistingNode->getFunction() == CS.getCalledFunction())
continue;
// If we are in checking mode, we are not allowed to actually mutate
// the callgraph. If this is a case where we can infer that the
// callgraph is less precise than it could be (e.g. an indirect call
// site could be turned direct), don't reject it in checking mode, and
// don't tweak it to be more precise.
if (CheckingMode && CS.getCalledFunction() &&
ExistingNode->getFunction() == 0)
continue;
assert(!CheckingMode &&
"CallGraphSCCPass did not update the CallGraph correctly!");
// If not, we either went from a direct call to indirect, indirect to
// direct, or direct to different direct.
CallGraphNode *CalleeNode;
if (Function *Callee = CS.getCalledFunction()) {
CalleeNode = CG.getOrInsertFunction(Callee);
// Keep track of whether we turned an indirect call into a direct
// one.
if (ExistingNode->getFunction() == 0) {
DevirtualizedCall = true;
DEBUG(dbgs() << " CGSCCPASSMGR: Devirtualized call to '"
<< Callee->getName() << "'\n");
}
} else {
CalleeNode = CG.getCallsExternalNode();
}
// Update the edge target in CGN.
CGN->replaceCallEdge(CS, CS, CalleeNode);
MadeChange = true;
continue;
}
assert(!CheckingMode &&
"CallGraphSCCPass did not update the CallGraph correctly!");
// If the call site didn't exist in the CGN yet, add it.
CallGraphNode *CalleeNode;
if (Function *Callee = CS.getCalledFunction()) {
CalleeNode = CG.getOrInsertFunction(Callee);
++NumDirectAdded;
} else {
CalleeNode = CG.getCallsExternalNode();
++NumIndirectAdded;
}
CGN->addCalledFunction(CS, CalleeNode);
MadeChange = true;
}
// We scanned the old callgraph node, removing invalidated call sites and
// then added back newly found call sites. One thing that can happen is
// that an old indirect call site was deleted and replaced with a new direct
// call. In this case, we have devirtualized a call, and CGSCCPM would like
// to iteratively optimize the new code. Unfortunately, we don't really
// have a great way to detect when this happens. As an approximation, we
// just look at whether the number of indirect calls is reduced and the
// number of direct calls is increased. There are tons of ways to fool this
// (e.g. DCE'ing an indirect call and duplicating an unrelated block with a
// direct call) but this is close enough.
if (NumIndirectRemoved > NumIndirectAdded &&
NumDirectRemoved < NumDirectAdded)
DevirtualizedCall = true;
// After scanning this function, if we still have entries in callsites, then
// they are dangling pointers. WeakVH should save us for this, so abort if
// this happens.
assert(CallSites.empty() && "Dangling pointers found in call sites map");
// Periodically do an explicit clear to remove tombstones when processing
// large scc's.
if ((FunctionNo & 15) == 15)
CallSites.clear();
}
DEBUG(if (MadeChange) {
dbgs() << "CGSCCPASSMGR: Refreshed SCC is now:\n";
for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
I != E; ++I)
(*I)->dump();
if (DevirtualizedCall)
dbgs() << "CGSCCPASSMGR: Refresh devirtualized a call!\n";
} else {
dbgs() << "CGSCCPASSMGR: SCC Refresh didn't change call graph.\n";
}
);
(void)MadeChange;
return DevirtualizedCall;
}
/// RunAllPassesOnSCC - Execute the body of the entire pass manager on the
/// specified SCC. This keeps track of whether a function pass devirtualizes
/// any calls and returns it in DevirtualizedCall.
bool CGPassManager::RunAllPassesOnSCC(CallGraphSCC &CurSCC, CallGraph &CG,
bool &DevirtualizedCall) {
bool Changed = false;
// CallGraphUpToDate - Keep track of whether the callgraph is known to be
// up-to-date or not. The CGSSC pass manager runs two types of passes:
// CallGraphSCC Passes and other random function passes. Because other
// random function passes are not CallGraph aware, they may clobber the
// call graph by introducing new calls or deleting other ones. This flag
// is set to false when we run a function pass so that we know to clean up
// the callgraph when we need to run a CGSCCPass again.
bool CallGraphUpToDate = true;
// Run all passes on current SCC.
for (unsigned PassNo = 0, e = getNumContainedPasses();
PassNo != e; ++PassNo) {
Pass *P = getContainedPass(PassNo);
// If we're in -debug-pass=Executions mode, construct the SCC node list,
// otherwise avoid constructing this string as it is expensive.
if (isPassDebuggingExecutionsOrMore()) {
std::string Functions;
#ifndef NDEBUG
raw_string_ostream OS(Functions);
for (CallGraphSCC::iterator I = CurSCC.begin(), E = CurSCC.end();
I != E; ++I) {
if (I != CurSCC.begin()) OS << ", ";
(*I)->print(OS);
}
OS.flush();
#endif
dumpPassInfo(P, EXECUTION_MSG, ON_CG_MSG, Functions);
}
dumpRequiredSet(P);
initializeAnalysisImpl(P);
// Actually run this pass on the current SCC.
Changed |= RunPassOnSCC(P, CurSCC, CG,
CallGraphUpToDate, DevirtualizedCall);
if (Changed)
dumpPassInfo(P, MODIFICATION_MSG, ON_CG_MSG, "");
dumpPreservedSet(P);
verifyPreservedAnalysis(P);
removeNotPreservedAnalysis(P);
recordAvailableAnalysis(P);
removeDeadPasses(P, "", ON_CG_MSG);
}
// If the callgraph was left out of date (because the last pass run was a
// functionpass), refresh it before we move on to the next SCC.
if (!CallGraphUpToDate)
DevirtualizedCall |= RefreshCallGraph(CurSCC, CG, false);
return Changed;
}
/// run - Execute all of the passes scheduled for execution. Keep track of
/// whether any of the passes modifies the module, and if so, return true.
bool CGPassManager::runOnModule(Module &M) {
CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
bool Changed = doInitialization(CG);
// Walk the callgraph in bottom-up SCC order.
scc_iterator<CallGraph*> CGI = scc_begin(&CG);
CallGraphSCC CurSCC(&CGI);
while (!CGI.isAtEnd()) {
// Copy the current SCC and increment past it so that the pass can hack
// on the SCC if it wants to without invalidating our iterator.
std::vector<CallGraphNode*> &NodeVec = *CGI;
CurSCC.initialize(&NodeVec[0], &NodeVec[0]+NodeVec.size());
++CGI;
// At the top level, we run all the passes in this pass manager on the
// functions in this SCC. However, we support iterative compilation in the
// case where a function pass devirtualizes a call to a function. For
// example, it is very common for a function pass (often GVN or instcombine)
// to eliminate the addressing that feeds into a call. With that improved
// information, we would like the call to be an inline candidate, infer
// mod-ref information etc.
//
// Because of this, we allow iteration up to a specified iteration count.
// This only happens in the case of a devirtualized call, so we only burn
// compile time in the case that we're making progress. We also have a hard
// iteration count limit in case there is crazy code.
unsigned Iteration = 0;
bool DevirtualizedCall = false;
do {
DEBUG(if (Iteration)
dbgs() << " SCCPASSMGR: Re-visiting SCC, iteration #"
<< Iteration << '\n');
DevirtualizedCall = false;
Changed |= RunAllPassesOnSCC(CurSCC, CG, DevirtualizedCall);
} while (Iteration++ < MaxIterations && DevirtualizedCall);
if (DevirtualizedCall)
DEBUG(dbgs() << " CGSCCPASSMGR: Stopped iteration after " << Iteration
<< " times, due to -max-cg-scc-iterations\n");
if (Iteration > MaxSCCIterations)
MaxSCCIterations = Iteration;
}
Changed |= doFinalization(CG);
return Changed;
}
/// Initialize CG
bool CGPassManager::doInitialization(CallGraph &CG) {
bool Changed = false;
for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
"Invalid CGPassManager member");
Changed |= ((FPPassManager*)PM)->doInitialization(CG.getModule());
} else {
Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doInitialization(CG);
}
}
return Changed;
}
/// Finalize CG
bool CGPassManager::doFinalization(CallGraph &CG) {
bool Changed = false;
for (unsigned i = 0, e = getNumContainedPasses(); i != e; ++i) {
if (PMDataManager *PM = getContainedPass(i)->getAsPMDataManager()) {
assert(PM->getPassManagerType() == PMT_FunctionPassManager &&
"Invalid CGPassManager member");
Changed |= ((FPPassManager*)PM)->doFinalization(CG.getModule());
} else {
Changed |= ((CallGraphSCCPass*)getContainedPass(i))->doFinalization(CG);
}
}
return Changed;
}
//===----------------------------------------------------------------------===//
// CallGraphSCC Implementation
//===----------------------------------------------------------------------===//
/// ReplaceNode - This informs the SCC and the pass manager that the specified
/// Old node has been deleted, and New is to be used in its place.
void CallGraphSCC::ReplaceNode(CallGraphNode *Old, CallGraphNode *New) {
assert(Old != New && "Should not replace node with self");
for (unsigned i = 0; ; ++i) {
assert(i != Nodes.size() && "Node not in SCC");
if (Nodes[i] != Old) continue;
Nodes[i] = New;
break;
}
// Update the active scc_iterator so that it doesn't contain dangling
// pointers to the old CallGraphNode.
scc_iterator<CallGraph*> *CGI = (scc_iterator<CallGraph*>*)Context;
CGI->ReplaceNode(Old, New);
}
//===----------------------------------------------------------------------===//
// CallGraphSCCPass Implementation
//===----------------------------------------------------------------------===//
/// Assign pass manager to manage this pass.
void CallGraphSCCPass::assignPassManager(PMStack &PMS,
PassManagerType PreferredType) {
// Find CGPassManager
while (!PMS.empty() &&
PMS.top()->getPassManagerType() > PMT_CallGraphPassManager)
PMS.pop();
assert(!PMS.empty() && "Unable to handle Call Graph Pass");
CGPassManager *CGP;
if (PMS.top()->getPassManagerType() == PMT_CallGraphPassManager)
CGP = (CGPassManager*)PMS.top();
else {
// Create new Call Graph SCC Pass Manager if it does not exist.
assert(!PMS.empty() && "Unable to create Call Graph Pass Manager");
PMDataManager *PMD = PMS.top();
// [1] Create new Call Graph Pass Manager
CGP = new CGPassManager();
// [2] Set up new manager's top level manager
PMTopLevelManager *TPM = PMD->getTopLevelManager();
TPM->addIndirectPassManager(CGP);
// [3] Assign manager to manage this new manager. This may create
// and push new managers into PMS
Pass *P = CGP;
TPM->schedulePass(P);
// [4] Push new manager into PMS
PMS.push(CGP);
}
CGP->add(this);
}
/// getAnalysisUsage - For this class, we declare that we require and preserve
/// the call graph. If the derived class implements this method, it should
/// always explicitly call the implementation here.
void CallGraphSCCPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<CallGraphWrapperPass>();
AU.addPreserved<CallGraphWrapperPass>();
}
//===----------------------------------------------------------------------===//
// PrintCallGraphPass Implementation
//===----------------------------------------------------------------------===//
namespace {
/// PrintCallGraphPass - Print a Module corresponding to a call graph.
///
class PrintCallGraphPass : public CallGraphSCCPass {
std::string Banner;
raw_ostream &Out; // raw_ostream to print on.
public:
static char ID;
PrintCallGraphPass(const std::string &B, raw_ostream &o)
: CallGraphSCCPass(ID), Banner(B), Out(o) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
bool runOnSCC(CallGraphSCC &SCC) {
Out << Banner;
for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
(*I)->getFunction()->print(Out);
return false;
}
};
} // end anonymous namespace.
char PrintCallGraphPass::ID = 0;
Pass *CallGraphSCCPass::createPrinterPass(raw_ostream &O,
const std::string &Banner) const {
return new PrintCallGraphPass(Banner, O);
}
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