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//===- CGSCCPassManager.cpp - Managing & running CGSCC passes -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/CGSCCPassManager.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/PriorityWorklist.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Analysis/LazyCallGraph.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/PassManagerImpl.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TimeProfiler.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <iterator>
#include <optional>
#define DEBUG_TYPE "cgscc"
using namespace llvm;
// Explicit template instantiations and specialization definitions for core
// template typedefs.
namespace llvm {
static cl::opt<bool> AbortOnMaxDevirtIterationsReached(
"abort-on-max-devirt-iterations-reached",
cl::desc("Abort when the max iterations for devirtualization CGSCC repeat "
"pass is reached"));
AnalysisKey ShouldNotRunFunctionPassesAnalysis::Key;
// Explicit instantiations for the core proxy templates.
template class AllAnalysesOn<LazyCallGraph::SCC>;
template class AnalysisManager<LazyCallGraph::SCC, LazyCallGraph &>;
template class PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager,
LazyCallGraph &, CGSCCUpdateResult &>;
template class InnerAnalysisManagerProxy<CGSCCAnalysisManager, Module>;
template class OuterAnalysisManagerProxy<ModuleAnalysisManager,
LazyCallGraph::SCC, LazyCallGraph &>;
template class OuterAnalysisManagerProxy<CGSCCAnalysisManager, Function>;
/// Explicitly specialize the pass manager run method to handle call graph
/// updates.
template <>
PreservedAnalyses
PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
CGSCCUpdateResult &>::run(LazyCallGraph::SCC &InitialC,
CGSCCAnalysisManager &AM,
LazyCallGraph &G, CGSCCUpdateResult &UR) {
// Request PassInstrumentation from analysis manager, will use it to run
// instrumenting callbacks for the passes later.
PassInstrumentation PI =
AM.getResult<PassInstrumentationAnalysis>(InitialC, G);
PreservedAnalyses PA = PreservedAnalyses::all();
// The SCC may be refined while we are running passes over it, so set up
// a pointer that we can update.
LazyCallGraph::SCC *C = &InitialC;
// Get Function analysis manager from its proxy.
FunctionAnalysisManager &FAM =
AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*C)->getManager();
for (auto &Pass : Passes) {
// Check the PassInstrumentation's BeforePass callbacks before running the
// pass, skip its execution completely if asked to (callback returns false).
if (!PI.runBeforePass(*Pass, *C))
continue;
PreservedAnalyses PassPA = Pass->run(*C, AM, G, UR);
if (UR.InvalidatedSCCs.count(C))
PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
else
PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
// Update the SCC if necessary.
C = UR.UpdatedC ? UR.UpdatedC : C;
if (UR.UpdatedC) {
// If C is updated, also create a proxy and update FAM inside the result.
auto *ResultFAMCP =
&AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G);
ResultFAMCP->updateFAM(FAM);
}
// Intersect the final preserved analyses to compute the aggregate
// preserved set for this pass manager.
PA.intersect(PassPA);
// If the CGSCC pass wasn't able to provide a valid updated SCC, the
// current SCC may simply need to be skipped if invalid.
if (UR.InvalidatedSCCs.count(C)) {
LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
break;
}
// Check that we didn't miss any update scenario.
assert(C->begin() != C->end() && "Cannot have an empty SCC!");
// Update the analysis manager as each pass runs and potentially
// invalidates analyses.
AM.invalidate(*C, PassPA);
}
// Before we mark all of *this* SCC's analyses as preserved below, intersect
// this with the cross-SCC preserved analysis set. This is used to allow
// CGSCC passes to mutate ancestor SCCs and still trigger proper invalidation
// for them.
UR.CrossSCCPA.intersect(PA);
// Invalidation was handled after each pass in the above loop for the current
// SCC. Therefore, the remaining analysis results in the AnalysisManager are
// preserved. We mark this with a set so that we don't need to inspect each
// one individually.
PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
return PA;
}
PreservedAnalyses
ModuleToPostOrderCGSCCPassAdaptor::run(Module &M, ModuleAnalysisManager &AM) {
// Setup the CGSCC analysis manager from its proxy.
CGSCCAnalysisManager &CGAM =
AM.getResult<CGSCCAnalysisManagerModuleProxy>(M).getManager();
// Get the call graph for this module.
LazyCallGraph &CG = AM.getResult<LazyCallGraphAnalysis>(M);
// Get Function analysis manager from its proxy.
FunctionAnalysisManager &FAM =
AM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M)->getManager();
// We keep worklists to allow us to push more work onto the pass manager as
// the passes are run.
SmallPriorityWorklist<LazyCallGraph::RefSCC *, 1> RCWorklist;
SmallPriorityWorklist<LazyCallGraph::SCC *, 1> CWorklist;
// Keep sets for invalidated SCCs and RefSCCs that should be skipped when
// iterating off the worklists.
SmallPtrSet<LazyCallGraph::RefSCC *, 4> InvalidRefSCCSet;
SmallPtrSet<LazyCallGraph::SCC *, 4> InvalidSCCSet;
SmallDenseSet<std::pair<LazyCallGraph::Node *, LazyCallGraph::SCC *>, 4>
InlinedInternalEdges;
CGSCCUpdateResult UR = {
RCWorklist, CWorklist, InvalidRefSCCSet,
InvalidSCCSet, nullptr, PreservedAnalyses::all(),
InlinedInternalEdges, {}};
// Request PassInstrumentation from analysis manager, will use it to run
// instrumenting callbacks for the passes later.
PassInstrumentation PI = AM.getResult<PassInstrumentationAnalysis>(M);
PreservedAnalyses PA = PreservedAnalyses::all();
CG.buildRefSCCs();
for (LazyCallGraph::RefSCC &RC :
llvm::make_early_inc_range(CG.postorder_ref_sccs())) {
assert(RCWorklist.empty() &&
"Should always start with an empty RefSCC worklist");
// The postorder_ref_sccs range we are walking is lazily constructed, so
// we only push the first one onto the worklist. The worklist allows us
// to capture *new* RefSCCs created during transformations.
//
// We really want to form RefSCCs lazily because that makes them cheaper
// to update as the program is simplified and allows us to have greater
// cache locality as forming a RefSCC touches all the parts of all the
// functions within that RefSCC.
//
// We also eagerly increment the iterator to the next position because
// the CGSCC passes below may delete the current RefSCC.
RCWorklist.insert(&RC);
do {
LazyCallGraph::RefSCC *RC = RCWorklist.pop_back_val();
if (InvalidRefSCCSet.count(RC)) {
LLVM_DEBUG(dbgs() << "Skipping an invalid RefSCC...\n");
continue;
}
assert(CWorklist.empty() &&
"Should always start with an empty SCC worklist");
LLVM_DEBUG(dbgs() << "Running an SCC pass across the RefSCC: " << *RC
<< "\n");
// The top of the worklist may *also* be the same SCC we just ran over
// (and invalidated for). Keep track of that last SCC we processed due
// to SCC update to avoid redundant processing when an SCC is both just
// updated itself and at the top of the worklist.
LazyCallGraph::SCC *LastUpdatedC = nullptr;
// Push the initial SCCs in reverse post-order as we'll pop off the
// back and so see this in post-order.
for (LazyCallGraph::SCC &C : llvm::reverse(*RC))
CWorklist.insert(&C);
do {
LazyCallGraph::SCC *C = CWorklist.pop_back_val();
// Due to call graph mutations, we may have invalid SCCs or SCCs from
// other RefSCCs in the worklist. The invalid ones are dead and the
// other RefSCCs should be queued above, so we just need to skip both
// scenarios here.
if (InvalidSCCSet.count(C)) {
LLVM_DEBUG(dbgs() << "Skipping an invalid SCC...\n");
continue;
}
if (LastUpdatedC == C) {
LLVM_DEBUG(dbgs() << "Skipping redundant run on SCC: " << *C << "\n");
continue;
}
// We used to also check if the current SCC is part of the current
// RefSCC and bail if it wasn't, since it should be in RCWorklist.
// However, this can cause compile time explosions in some cases on
// modules with a huge RefSCC. If a non-trivial amount of SCCs in the
// huge RefSCC can become their own child RefSCC, we create one child
// RefSCC, bail on the current RefSCC, visit the child RefSCC, revisit
// the huge RefSCC, and repeat. By visiting all SCCs in the original
// RefSCC we create all the child RefSCCs in one pass of the RefSCC,
// rather one pass of the RefSCC creating one child RefSCC at a time.
// Ensure we can proxy analysis updates from the CGSCC analysis manager
// into the the Function analysis manager by getting a proxy here.
// This also needs to update the FunctionAnalysisManager, as this may be
// the first time we see this SCC.
CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
FAM);
// Each time we visit a new SCC pulled off the worklist,
// a transformation of a child SCC may have also modified this parent
// and invalidated analyses. So we invalidate using the update record's
// cross-SCC preserved set. This preserved set is intersected by any
// CGSCC pass that handles invalidation (primarily pass managers) prior
// to marking its SCC as preserved. That lets us track everything that
// might need invalidation across SCCs without excessive invalidations
// on a single SCC.
//
// This essentially allows SCC passes to freely invalidate analyses
// of any ancestor SCC. If this becomes detrimental to successfully
// caching analyses, we could force each SCC pass to manually
// invalidate the analyses for any SCCs other than themselves which
// are mutated. However, that seems to lose the robustness of the
// pass-manager driven invalidation scheme.
CGAM.invalidate(*C, UR.CrossSCCPA);
do {
// Check that we didn't miss any update scenario.
assert(!InvalidSCCSet.count(C) && "Processing an invalid SCC!");
assert(C->begin() != C->end() && "Cannot have an empty SCC!");
LastUpdatedC = UR.UpdatedC;
UR.UpdatedC = nullptr;
// Check the PassInstrumentation's BeforePass callbacks before
// running the pass, skip its execution completely if asked to
// (callback returns false).
if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
continue;
PreservedAnalyses PassPA = Pass->run(*C, CGAM, CG, UR);
if (UR.InvalidatedSCCs.count(C))
PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
else
PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
// Update the SCC and RefSCC if necessary.
C = UR.UpdatedC ? UR.UpdatedC : C;
if (UR.UpdatedC) {
// If we're updating the SCC, also update the FAM inside the proxy's
// result.
CGAM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG).updateFAM(
FAM);
}
// Intersect with the cross-SCC preserved set to capture any
// cross-SCC invalidation.
UR.CrossSCCPA.intersect(PassPA);
// Intersect the preserved set so that invalidation of module
// analyses will eventually occur when the module pass completes.
PA.intersect(PassPA);
// If the CGSCC pass wasn't able to provide a valid updated SCC,
// the current SCC may simply need to be skipped if invalid.
if (UR.InvalidatedSCCs.count(C)) {
LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
break;
}
// Check that we didn't miss any update scenario.
assert(C->begin() != C->end() && "Cannot have an empty SCC!");
// We handle invalidating the CGSCC analysis manager's information
// for the (potentially updated) SCC here. Note that any other SCCs
// whose structure has changed should have been invalidated by
// whatever was updating the call graph. This SCC gets invalidated
// late as it contains the nodes that were actively being
// processed.
CGAM.invalidate(*C, PassPA);
// The pass may have restructured the call graph and refined the
// current SCC and/or RefSCC. We need to update our current SCC and
// RefSCC pointers to follow these. Also, when the current SCC is
// refined, re-run the SCC pass over the newly refined SCC in order
// to observe the most precise SCC model available. This inherently
// cannot cycle excessively as it only happens when we split SCCs
// apart, at most converging on a DAG of single nodes.
// FIXME: If we ever start having RefSCC passes, we'll want to
// iterate there too.
if (UR.UpdatedC)
LLVM_DEBUG(dbgs()
<< "Re-running SCC passes after a refinement of the "
"current SCC: "
<< *UR.UpdatedC << "\n");
// Note that both `C` and `RC` may at this point refer to deleted,
// invalid SCC and RefSCCs respectively. But we will short circuit
// the processing when we check them in the loop above.
} while (UR.UpdatedC);
} while (!CWorklist.empty());
// We only need to keep internal inlined edge information within
// a RefSCC, clear it to save on space and let the next time we visit
// any of these functions have a fresh start.
InlinedInternalEdges.clear();
} while (!RCWorklist.empty());
}
// By definition we preserve the call garph, all SCC analyses, and the
// analysis proxies by handling them above and in any nested pass managers.
PA.preserveSet<AllAnalysesOn<LazyCallGraph::SCC>>();
PA.preserve<LazyCallGraphAnalysis>();
PA.preserve<CGSCCAnalysisManagerModuleProxy>();
PA.preserve<FunctionAnalysisManagerModuleProxy>();
return PA;
}
PreservedAnalyses DevirtSCCRepeatedPass::run(LazyCallGraph::SCC &InitialC,
CGSCCAnalysisManager &AM,
LazyCallGraph &CG,
CGSCCUpdateResult &UR) {
PreservedAnalyses PA = PreservedAnalyses::all();
PassInstrumentation PI =
AM.getResult<PassInstrumentationAnalysis>(InitialC, CG);
// The SCC may be refined while we are running passes over it, so set up
// a pointer that we can update.
LazyCallGraph::SCC *C = &InitialC;
// Struct to track the counts of direct and indirect calls in each function
// of the SCC.
struct CallCount {
int Direct;
int Indirect;
};
// Put value handles on all of the indirect calls and return the number of
// direct calls for each function in the SCC.
auto ScanSCC = [](LazyCallGraph::SCC &C,
SmallMapVector<Value *, WeakTrackingVH, 16> &CallHandles) {
assert(CallHandles.empty() && "Must start with a clear set of handles.");
SmallDenseMap<Function *, CallCount> CallCounts;
CallCount CountLocal = {0, 0};
for (LazyCallGraph::Node &N : C) {
CallCount &Count =
CallCounts.insert(std::make_pair(&N.getFunction(), CountLocal))
.first->second;
for (Instruction &I : instructions(N.getFunction()))
if (auto *CB = dyn_cast<CallBase>(&I)) {
if (CB->getCalledFunction()) {
++Count.Direct;
} else {
++Count.Indirect;
CallHandles.insert({CB, WeakTrackingVH(CB)});
}
}
}
return CallCounts;
};
UR.IndirectVHs.clear();
// Populate the initial call handles and get the initial call counts.
auto CallCounts = ScanSCC(*C, UR.IndirectVHs);
for (int Iteration = 0;; ++Iteration) {
if (!PI.runBeforePass<LazyCallGraph::SCC>(*Pass, *C))
continue;
PreservedAnalyses PassPA = Pass->run(*C, AM, CG, UR);
if (UR.InvalidatedSCCs.count(C))
PI.runAfterPassInvalidated<LazyCallGraph::SCC>(*Pass, PassPA);
else
PI.runAfterPass<LazyCallGraph::SCC>(*Pass, *C, PassPA);
PA.intersect(PassPA);
// If the SCC structure has changed, bail immediately and let the outer
// CGSCC layer handle any iteration to reflect the refined structure.
if (UR.UpdatedC && UR.UpdatedC != C)
break;
// If the CGSCC pass wasn't able to provide a valid updated SCC, the
// current SCC may simply need to be skipped if invalid.
if (UR.InvalidatedSCCs.count(C)) {
LLVM_DEBUG(dbgs() << "Skipping invalidated root or island SCC!\n");
break;
}
assert(C->begin() != C->end() && "Cannot have an empty SCC!");
// Check whether any of the handles were devirtualized.
bool Devirt = llvm::any_of(UR.IndirectVHs, [](auto &P) -> bool {
if (P.second) {
if (CallBase *CB = dyn_cast<CallBase>(P.second)) {
if (CB->getCalledFunction()) {
LLVM_DEBUG(dbgs() << "Found devirtualized call: " << *CB << "\n");
return true;
}
}
}
return false;
});
// Rescan to build up a new set of handles and count how many direct
// calls remain. If we decide to iterate, this also sets up the input to
// the next iteration.
UR.IndirectVHs.clear();
auto NewCallCounts = ScanSCC(*C, UR.IndirectVHs);
// If we haven't found an explicit devirtualization already see if we
// have decreased the number of indirect calls and increased the number
// of direct calls for any function in the SCC. This can be fooled by all
// manner of transformations such as DCE and other things, but seems to
// work well in practice.
if (!Devirt)
// Iterate over the keys in NewCallCounts, if Function also exists in
// CallCounts, make the check below.
for (auto &Pair : NewCallCounts) {
auto &CallCountNew = Pair.second;
auto CountIt = CallCounts.find(Pair.first);
if (CountIt != CallCounts.end()) {
const auto &CallCountOld = CountIt->second;
if (CallCountOld.Indirect > CallCountNew.Indirect &&
CallCountOld.Direct < CallCountNew.Direct) {
Devirt = true;
break;
}
}
}
if (!Devirt) {
break;
}
// Otherwise, if we've already hit our max, we're done.
if (Iteration >= MaxIterations) {
if (AbortOnMaxDevirtIterationsReached)
report_fatal_error("Max devirtualization iterations reached");
LLVM_DEBUG(
dbgs() << "Found another devirtualization after hitting the max "
"number of repetitions ("
<< MaxIterations << ") on SCC: " << *C << "\n");
break;
}
LLVM_DEBUG(
dbgs() << "Repeating an SCC pass after finding a devirtualization in: "
<< *C << "\n");
// Move over the new call counts in preparation for iterating.
CallCounts = std::move(NewCallCounts);
// Update the analysis manager with each run and intersect the total set
// of preserved analyses so we're ready to iterate.
AM.invalidate(*C, PassPA);
}
// Note that we don't add any preserved entries here unlike a more normal
// "pass manager" because we only handle invalidation *between* iterations,
// not after the last iteration.
return PA;
}
PreservedAnalyses CGSCCToFunctionPassAdaptor::run(LazyCallGraph::SCC &C,
CGSCCAnalysisManager &AM,
LazyCallGraph &CG,
CGSCCUpdateResult &UR) {
// Setup the function analysis manager from its proxy.
FunctionAnalysisManager &FAM =
AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, CG).getManager();
SmallVector<LazyCallGraph::Node *, 4> Nodes;
for (LazyCallGraph::Node &N : C)
Nodes.push_back(&N);
// The SCC may get split while we are optimizing functions due to deleting
// edges. If this happens, the current SCC can shift, so keep track of
// a pointer we can overwrite.
LazyCallGraph::SCC *CurrentC = &C;
LLVM_DEBUG(dbgs() << "Running function passes across an SCC: " << C << "\n");
PreservedAnalyses PA = PreservedAnalyses::all();
for (LazyCallGraph::Node *N : Nodes) {
// Skip nodes from other SCCs. These may have been split out during
// processing. We'll eventually visit those SCCs and pick up the nodes
// there.
if (CG.lookupSCC(*N) != CurrentC)
continue;
Function &F = N->getFunction();
if (NoRerun && FAM.getCachedResult<ShouldNotRunFunctionPassesAnalysis>(F))
continue;
PassInstrumentation PI = FAM.getResult<PassInstrumentationAnalysis>(F);
if (!PI.runBeforePass<Function>(*Pass, F))
continue;
PreservedAnalyses PassPA = Pass->run(F, FAM);
PI.runAfterPass<Function>(*Pass, F, PassPA);
// We know that the function pass couldn't have invalidated any other
// function's analyses (that's the contract of a function pass), so
// directly handle the function analysis manager's invalidation here.
FAM.invalidate(F, EagerlyInvalidate ? PreservedAnalyses::none() : PassPA);
if (NoRerun)
(void)FAM.getResult<ShouldNotRunFunctionPassesAnalysis>(F);
// Then intersect the preserved set so that invalidation of module
// analyses will eventually occur when the module pass completes.
PA.intersect(std::move(PassPA));
// If the call graph hasn't been preserved, update it based on this
// function pass. This may also update the current SCC to point to
// a smaller, more refined SCC.
auto PAC = PA.getChecker<LazyCallGraphAnalysis>();
if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<Module>>()) {
CurrentC = &updateCGAndAnalysisManagerForFunctionPass(CG, *CurrentC, *N,
AM, UR, FAM);
assert(CG.lookupSCC(*N) == CurrentC &&
"Current SCC not updated to the SCC containing the current node!");
}
}
// By definition we preserve the proxy. And we preserve all analyses on
// Functions. This precludes *any* invalidation of function analyses by the
// proxy, but that's OK because we've taken care to invalidate analyses in
// the function analysis manager incrementally above.
PA.preserveSet<AllAnalysesOn<Function>>();
PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
// We've also ensured that we updated the call graph along the way.
PA.preserve<LazyCallGraphAnalysis>();
return PA;
}
bool CGSCCAnalysisManagerModuleProxy::Result::invalidate(
Module &M, const PreservedAnalyses &PA,
ModuleAnalysisManager::Invalidator &Inv) {
// If literally everything is preserved, we're done.
if (PA.areAllPreserved())
return false; // This is still a valid proxy.
// If this proxy or the call graph is going to be invalidated, we also need
// to clear all the keys coming from that analysis.
//
// We also directly invalidate the FAM's module proxy if necessary, and if
// that proxy isn't preserved we can't preserve this proxy either. We rely on
// it to handle module -> function analysis invalidation in the face of
// structural changes and so if it's unavailable we conservatively clear the
// entire SCC layer as well rather than trying to do invalidation ourselves.
auto PAC = PA.getChecker<CGSCCAnalysisManagerModuleProxy>();
if (!(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Module>>()) ||
Inv.invalidate<LazyCallGraphAnalysis>(M, PA) ||
Inv.invalidate<FunctionAnalysisManagerModuleProxy>(M, PA)) {
InnerAM->clear();
// And the proxy itself should be marked as invalid so that we can observe
// the new call graph. This isn't strictly necessary because we cheat
// above, but is still useful.
return true;
}
// Directly check if the relevant set is preserved so we can short circuit
// invalidating SCCs below.
bool AreSCCAnalysesPreserved =
PA.allAnalysesInSetPreserved<AllAnalysesOn<LazyCallGraph::SCC>>();
// Ok, we have a graph, so we can propagate the invalidation down into it.
G->buildRefSCCs();
for (auto &RC : G->postorder_ref_sccs())
for (auto &C : RC) {
std::optional<PreservedAnalyses> InnerPA;
// Check to see whether the preserved set needs to be adjusted based on
// module-level analysis invalidation triggering deferred invalidation
// for this SCC.
if (auto *OuterProxy =
InnerAM->getCachedResult<ModuleAnalysisManagerCGSCCProxy>(C))
for (const auto &OuterInvalidationPair :
OuterProxy->getOuterInvalidations()) {
AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
if (Inv.invalidate(OuterAnalysisID, M, PA)) {
if (!InnerPA)
InnerPA = PA;
for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
InnerPA->abandon(InnerAnalysisID);
}
}
// Check if we needed a custom PA set. If so we'll need to run the inner
// invalidation.
if (InnerPA) {
InnerAM->invalidate(C, *InnerPA);
continue;
}
// Otherwise we only need to do invalidation if the original PA set didn't
// preserve all SCC analyses.
if (!AreSCCAnalysesPreserved)
InnerAM->invalidate(C, PA);
}
// Return false to indicate that this result is still a valid proxy.
return false;
}
template <>
CGSCCAnalysisManagerModuleProxy::Result
CGSCCAnalysisManagerModuleProxy::run(Module &M, ModuleAnalysisManager &AM) {
// Force the Function analysis manager to also be available so that it can
// be accessed in an SCC analysis and proxied onward to function passes.
// FIXME: It is pretty awkward to just drop the result here and assert that
// we can find it again later.
(void)AM.getResult<FunctionAnalysisManagerModuleProxy>(M);
return Result(*InnerAM, AM.getResult<LazyCallGraphAnalysis>(M));
}
AnalysisKey FunctionAnalysisManagerCGSCCProxy::Key;
FunctionAnalysisManagerCGSCCProxy::Result
FunctionAnalysisManagerCGSCCProxy::run(LazyCallGraph::SCC &C,
CGSCCAnalysisManager &AM,
LazyCallGraph &CG) {
// Note: unconditionally getting checking that the proxy exists may get it at
// this point. There are cases when this is being run unnecessarily, but
// it is cheap and having the assertion in place is more valuable.
auto &MAMProxy = AM.getResult<ModuleAnalysisManagerCGSCCProxy>(C, CG);
Module &M = *C.begin()->getFunction().getParent();
bool ProxyExists =
MAMProxy.cachedResultExists<FunctionAnalysisManagerModuleProxy>(M);
assert(ProxyExists &&
"The CGSCC pass manager requires that the FAM module proxy is run "
"on the module prior to entering the CGSCC walk");
(void)ProxyExists;
// We just return an empty result. The caller will use the updateFAM interface
// to correctly register the relevant FunctionAnalysisManager based on the
// context in which this proxy is run.
return Result();
}
bool FunctionAnalysisManagerCGSCCProxy::Result::invalidate(
LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
CGSCCAnalysisManager::Invalidator &Inv) {
// If literally everything is preserved, we're done.
if (PA.areAllPreserved())
return false; // This is still a valid proxy.
// All updates to preserve valid results are done below, so we don't need to
// invalidate this proxy.
//
// Note that in order to preserve this proxy, a module pass must ensure that
// the FAM has been completely updated to handle the deletion of functions.
// Specifically, any FAM-cached results for those functions need to have been
// forcibly cleared. When preserved, this proxy will only invalidate results
// cached on functions *still in the module* at the end of the module pass.
auto PAC = PA.getChecker<FunctionAnalysisManagerCGSCCProxy>();
if (!PAC.preserved() && !PAC.preservedSet<AllAnalysesOn<LazyCallGraph::SCC>>()) {
for (LazyCallGraph::Node &N : C)
FAM->invalidate(N.getFunction(), PA);
return false;
}
// Directly check if the relevant set is preserved.
bool AreFunctionAnalysesPreserved =
PA.allAnalysesInSetPreserved<AllAnalysesOn<Function>>();
// Now walk all the functions to see if any inner analysis invalidation is
// necessary.
for (LazyCallGraph::Node &N : C) {
Function &F = N.getFunction();
std::optional<PreservedAnalyses> FunctionPA;
// Check to see whether the preserved set needs to be pruned based on
// SCC-level analysis invalidation that triggers deferred invalidation
// registered with the outer analysis manager proxy for this function.
if (auto *OuterProxy =
FAM->getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F))
for (const auto &OuterInvalidationPair :
OuterProxy->getOuterInvalidations()) {
AnalysisKey *OuterAnalysisID = OuterInvalidationPair.first;
const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
if (Inv.invalidate(OuterAnalysisID, C, PA)) {
if (!FunctionPA)
FunctionPA = PA;
for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
FunctionPA->abandon(InnerAnalysisID);
}
}
// Check if we needed a custom PA set, and if so we'll need to run the
// inner invalidation.
if (FunctionPA) {
FAM->invalidate(F, *FunctionPA);
continue;
}
// Otherwise we only need to do invalidation if the original PA set didn't
// preserve all function analyses.
if (!AreFunctionAnalysesPreserved)
FAM->invalidate(F, PA);
}
// Return false to indicate that this result is still a valid proxy.
return false;
}
} // end namespace llvm
/// When a new SCC is created for the graph we first update the
/// FunctionAnalysisManager in the Proxy's result.
/// As there might be function analysis results cached for the functions now in
/// that SCC, two forms of updates are required.
///
/// First, a proxy from the SCC to the FunctionAnalysisManager needs to be
/// created so that any subsequent invalidation events to the SCC are
/// propagated to the function analysis results cached for functions within it.
///
/// Second, if any of the functions within the SCC have analysis results with
/// outer analysis dependencies, then those dependencies would point to the
/// *wrong* SCC's analysis result. We forcibly invalidate the necessary
/// function analyses so that they don't retain stale handles.
static void updateNewSCCFunctionAnalyses(LazyCallGraph::SCC &C,
LazyCallGraph &G,
CGSCCAnalysisManager &AM,
FunctionAnalysisManager &FAM) {
AM.getResult<FunctionAnalysisManagerCGSCCProxy>(C, G).updateFAM(FAM);
// Now walk the functions in this SCC and invalidate any function analysis
// results that might have outer dependencies on an SCC analysis.
for (LazyCallGraph::Node &N : C) {
Function &F = N.getFunction();
auto *OuterProxy =
FAM.getCachedResult<CGSCCAnalysisManagerFunctionProxy>(F);
if (!OuterProxy)
// No outer analyses were queried, nothing to do.
continue;
// Forcibly abandon all the inner analyses with dependencies, but
// invalidate nothing else.
auto PA = PreservedAnalyses::all();
for (const auto &OuterInvalidationPair :
OuterProxy->getOuterInvalidations()) {
const auto &InnerAnalysisIDs = OuterInvalidationPair.second;
for (AnalysisKey *InnerAnalysisID : InnerAnalysisIDs)
PA.abandon(InnerAnalysisID);
}
// Now invalidate anything we found.
FAM.invalidate(F, PA);
}
}
/// Helper function to update both the \c CGSCCAnalysisManager \p AM and the \c
/// CGSCCPassManager's \c CGSCCUpdateResult \p UR based on a range of newly
/// added SCCs.
///
/// The range of new SCCs must be in postorder already. The SCC they were split
/// out of must be provided as \p C. The current node being mutated and
/// triggering updates must be passed as \p N.
///
/// This function returns the SCC containing \p N. This will be either \p C if
/// no new SCCs have been split out, or it will be the new SCC containing \p N.
template <typename SCCRangeT>
static LazyCallGraph::SCC *
incorporateNewSCCRange(const SCCRangeT &NewSCCRange, LazyCallGraph &G,
LazyCallGraph::Node &N, LazyCallGraph::SCC *C,
CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR) {
using SCC = LazyCallGraph::SCC;
if (NewSCCRange.empty())
return C;
// Add the current SCC to the worklist as its shape has changed.
UR.CWorklist.insert(C);
LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist:" << *C
<< "\n");
SCC *OldC = C;
// Update the current SCC. Note that if we have new SCCs, this must actually
// change the SCC.
assert(C != &*NewSCCRange.begin() &&
"Cannot insert new SCCs without changing current SCC!");
C = &*NewSCCRange.begin();
assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
// If we had a cached FAM proxy originally, we will want to create more of
// them for each SCC that was split off.
FunctionAnalysisManager *FAM = nullptr;
if (auto *FAMProxy =
AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(*OldC))
FAM = &FAMProxy->getManager();
// We need to propagate an invalidation call to all but the newly current SCC
// because the outer pass manager won't do that for us after splitting them.
// FIXME: We should accept a PreservedAnalysis from the CG updater so that if
// there are preserved analysis we can avoid invalidating them here for
// split-off SCCs.
// We know however that this will preserve any FAM proxy so go ahead and mark
// that.
auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
AM.invalidate(*OldC, PA);
// Ensure the now-current SCC's function analyses are updated.
if (FAM)
updateNewSCCFunctionAnalyses(*C, G, AM, *FAM);
for (SCC &NewC : llvm::reverse(llvm::drop_begin(NewSCCRange))) {
assert(C != &NewC && "No need to re-visit the current SCC!");
assert(OldC != &NewC && "Already handled the original SCC!");
UR.CWorklist.insert(&NewC);
LLVM_DEBUG(dbgs() << "Enqueuing a newly formed SCC:" << NewC << "\n");
// Ensure new SCCs' function analyses are updated.
if (FAM)
updateNewSCCFunctionAnalyses(NewC, G, AM, *FAM);
// Also propagate a normal invalidation to the new SCC as only the current
// will get one from the pass manager infrastructure.
AM.invalidate(NewC, PA);
}
return C;
}
static LazyCallGraph::SCC &updateCGAndAnalysisManagerForPass(
LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
FunctionAnalysisManager &FAM, bool FunctionPass) {
using Node = LazyCallGraph::Node;
using Edge = LazyCallGraph::Edge;
using SCC = LazyCallGraph::SCC;
using RefSCC = LazyCallGraph::RefSCC;
RefSCC &InitialRC = InitialC.getOuterRefSCC();
SCC *C = &InitialC;
RefSCC *RC = &InitialRC;
Function &F = N.getFunction();
// Walk the function body and build up the set of retained, promoted, and
// demoted edges.
SmallVector<Constant *, 16> Worklist;
SmallPtrSet<Constant *, 16> Visited;
SmallPtrSet<Node *, 16> RetainedEdges;
SmallSetVector<Node *, 4> PromotedRefTargets;
SmallSetVector<Node *, 4> DemotedCallTargets;
SmallSetVector<Node *, 4> NewCallEdges;
SmallSetVector<Node *, 4> NewRefEdges;
// First walk the function and handle all called functions. We do this first
// because if there is a single call edge, whether there are ref edges is
// irrelevant.
for (Instruction &I : instructions(F)) {
if (auto *CB = dyn_cast<CallBase>(&I)) {
if (Function *Callee = CB->getCalledFunction()) {
if (Visited.insert(Callee).second && !Callee->isDeclaration()) {
Node *CalleeN = G.lookup(*Callee);
assert(CalleeN &&
"Visited function should already have an associated node");
Edge *E = N->lookup(*CalleeN);
assert((E || !FunctionPass) &&
"No function transformations should introduce *new* "
"call edges! Any new calls should be modeled as "
"promoted existing ref edges!");
bool Inserted = RetainedEdges.insert(CalleeN).second;
(void)Inserted;
assert(Inserted && "We should never visit a function twice.");
if (!E)
NewCallEdges.insert(CalleeN);
else if (!E->isCall())
PromotedRefTargets.insert(CalleeN);
}
} else {
// We can miss devirtualization if an indirect call is created then
// promoted before updateCGAndAnalysisManagerForPass runs.
auto *Entry = UR.IndirectVHs.find(CB);
if (Entry == UR.IndirectVHs.end())
UR.IndirectVHs.insert({CB, WeakTrackingVH(CB)});
else if (!Entry->second)
Entry->second = WeakTrackingVH(CB);
}
}
}
// Now walk all references.
for (Instruction &I : instructions(F))
for (Value *Op : I.operand_values())
if (auto *OpC = dyn_cast<Constant>(Op))
if (Visited.insert(OpC).second)
Worklist.push_back(OpC);
auto VisitRef = [&](Function &Referee) {
Node *RefereeN = G.lookup(Referee);
assert(RefereeN &&
"Visited function should already have an associated node");
Edge *E = N->lookup(*RefereeN);
assert((E || !FunctionPass) &&
"No function transformations should introduce *new* ref "
"edges! Any new ref edges would require IPO which "
"function passes aren't allowed to do!");
bool Inserted = RetainedEdges.insert(RefereeN).second;
(void)Inserted;
assert(Inserted && "We should never visit a function twice.");
if (!E)
NewRefEdges.insert(RefereeN);
else if (E->isCall())
DemotedCallTargets.insert(RefereeN);
};
LazyCallGraph::visitReferences(Worklist, Visited, VisitRef);
// Handle new ref edges.
for (Node *RefTarget : NewRefEdges) {
SCC &TargetC = *G.lookupSCC(*RefTarget);
RefSCC &TargetRC = TargetC.getOuterRefSCC();
(void)TargetRC;
// TODO: This only allows trivial edges to be added for now.
#ifdef EXPENSIVE_CHECKS
assert((RC == &TargetRC ||
RC->isAncestorOf(TargetRC)) && "New ref edge is not trivial!");
#endif
RC->insertTrivialRefEdge(N, *RefTarget);
}
// Handle new call edges.
for (Node *CallTarget : NewCallEdges) {
SCC &TargetC = *G.lookupSCC(*CallTarget);
RefSCC &TargetRC = TargetC.getOuterRefSCC();
(void)TargetRC;
// TODO: This only allows trivial edges to be added for now.
#ifdef EXPENSIVE_CHECKS
assert((RC == &TargetRC ||
RC->isAncestorOf(TargetRC)) && "New call edge is not trivial!");
#endif
// Add a trivial ref edge to be promoted later on alongside
// PromotedRefTargets.
RC->insertTrivialRefEdge(N, *CallTarget);
}
// Include synthetic reference edges to known, defined lib functions.
for (auto *LibFn : G.getLibFunctions())
// While the list of lib functions doesn't have repeats, don't re-visit
// anything handled above.
if (!Visited.count(LibFn))
VisitRef(*LibFn);
// First remove all of the edges that are no longer present in this function.
// The first step makes these edges uniformly ref edges and accumulates them
// into a separate data structure so removal doesn't invalidate anything.
SmallVector<Node *, 4> DeadTargets;
for (Edge &E : *N) {
if (RetainedEdges.count(&E.getNode()))
continue;
SCC &TargetC = *G.lookupSCC(E.getNode());
RefSCC &TargetRC = TargetC.getOuterRefSCC();
if (&TargetRC == RC && E.isCall()) {
if (C != &TargetC) {
// For separate SCCs this is trivial.
RC->switchTrivialInternalEdgeToRef(N, E.getNode());
} else {
// Now update the call graph.
C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, E.getNode()),
G, N, C, AM, UR);
}
}
// Now that this is ready for actual removal, put it into our list.
DeadTargets.push_back(&E.getNode());
}
// Remove the easy cases quickly and actually pull them out of our list.
llvm::erase_if(DeadTargets, [&](Node *TargetN) {
SCC &TargetC = *G.lookupSCC(*TargetN);
RefSCC &TargetRC = TargetC.getOuterRefSCC();
// We can't trivially remove internal targets, so skip
// those.
if (&TargetRC == RC)
return false;
LLVM_DEBUG(dbgs() << "Deleting outgoing edge from '" << N << "' to '"
<< *TargetN << "'\n");
RC->removeOutgoingEdge(N, *TargetN);
return true;
});
// Now do a batch removal of the internal ref edges left.
auto NewRefSCCs = RC->removeInternalRefEdge(N, DeadTargets);
if (!NewRefSCCs.empty()) {
// The old RefSCC is dead, mark it as such.
UR.InvalidatedRefSCCs.insert(RC);
// Note that we don't bother to invalidate analyses as ref-edge
// connectivity is not really observable in any way and is intended
// exclusively to be used for ordering of transforms rather than for
// analysis conclusions.
// Update RC to the "bottom".
assert(G.lookupSCC(N) == C && "Changed the SCC when splitting RefSCCs!");
RC = &C->getOuterRefSCC();
assert(G.lookupRefSCC(N) == RC && "Failed to update current RefSCC!");
// The RC worklist is in reverse postorder, so we enqueue the new ones in
// RPO except for the one which contains the source node as that is the
// "bottom" we will continue processing in the bottom-up walk.
assert(NewRefSCCs.front() == RC &&
"New current RefSCC not first in the returned list!");
for (RefSCC *NewRC : llvm::reverse(llvm::drop_begin(NewRefSCCs))) {
assert(NewRC != RC && "Should not encounter the current RefSCC further "
"in the postorder list of new RefSCCs.");
UR.RCWorklist.insert(NewRC);
LLVM_DEBUG(dbgs() << "Enqueuing a new RefSCC in the update worklist: "
<< *NewRC << "\n");
}
}
// Next demote all the call edges that are now ref edges. This helps make
// the SCCs small which should minimize the work below as we don't want to
// form cycles that this would break.
for (Node *RefTarget : DemotedCallTargets) {
SCC &TargetC = *G.lookupSCC(*RefTarget);
RefSCC &TargetRC = TargetC.getOuterRefSCC();
// The easy case is when the target RefSCC is not this RefSCC. This is
// only supported when the target RefSCC is a child of this RefSCC.
if (&TargetRC != RC) {
#ifdef EXPENSIVE_CHECKS
assert(RC->isAncestorOf(TargetRC) &&
"Cannot potentially form RefSCC cycles here!");
#endif
RC->switchOutgoingEdgeToRef(N, *RefTarget);
LLVM_DEBUG(dbgs() << "Switch outgoing call edge to a ref edge from '" << N
<< "' to '" << *RefTarget << "'\n");
continue;
}
// We are switching an internal call edge to a ref edge. This may split up
// some SCCs.
if (C != &TargetC) {
// For separate SCCs this is trivial.
RC->switchTrivialInternalEdgeToRef(N, *RefTarget);
continue;
}
// Now update the call graph.
C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, *RefTarget), G, N,
C, AM, UR);
}
// We added a ref edge earlier for new call edges, promote those to call edges
// alongside PromotedRefTargets.
for (Node *E : NewCallEdges)
PromotedRefTargets.insert(E);
// Now promote ref edges into call edges.
for (Node *CallTarget : PromotedRefTargets) {
SCC &TargetC = *G.lookupSCC(*CallTarget);
RefSCC &TargetRC = TargetC.getOuterRefSCC();
// The easy case is when the target RefSCC is not this RefSCC. This is
// only supported when the target RefSCC is a child of this RefSCC.
if (&TargetRC != RC) {
#ifdef EXPENSIVE_CHECKS
assert(RC->isAncestorOf(TargetRC) &&
"Cannot potentially form RefSCC cycles here!");
#endif
RC->switchOutgoingEdgeToCall(N, *CallTarget);
LLVM_DEBUG(dbgs() << "Switch outgoing ref edge to a call edge from '" << N
<< "' to '" << *CallTarget << "'\n");
continue;
}
LLVM_DEBUG(dbgs() << "Switch an internal ref edge to a call edge from '"
<< N << "' to '" << *CallTarget << "'\n");
// Otherwise we are switching an internal ref edge to a call edge. This
// may merge away some SCCs, and we add those to the UpdateResult. We also
// need to make sure to update the worklist in the event SCCs have moved
// before the current one in the post-order sequence
bool HasFunctionAnalysisProxy = false;
auto InitialSCCIndex = RC->find(*C) - RC->begin();
bool FormedCycle = RC->switchInternalEdgeToCall(
N, *CallTarget, [&](ArrayRef<SCC *> MergedSCCs) {
for (SCC *MergedC : MergedSCCs) {
assert(MergedC != &TargetC && "Cannot merge away the target SCC!");
HasFunctionAnalysisProxy |=
AM.getCachedResult<FunctionAnalysisManagerCGSCCProxy>(
*MergedC) != nullptr;
// Mark that this SCC will no longer be valid.
UR.InvalidatedSCCs.insert(MergedC);
// FIXME: We should really do a 'clear' here to forcibly release
// memory, but we don't have a good way of doing that and
// preserving the function analyses.
auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
AM.invalidate(*MergedC, PA);
}
});
// If we formed a cycle by creating this call, we need to update more data
// structures.
if (FormedCycle) {
C = &TargetC;
assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
// If one of the invalidated SCCs had a cached proxy to a function
// analysis manager, we need to create a proxy in the new current SCC as
// the invalidated SCCs had their functions moved.
if (HasFunctionAnalysisProxy)
AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, G).updateFAM(FAM);
// Any analyses cached for this SCC are no longer precise as the shape
// has changed by introducing this cycle. However, we have taken care to
// update the proxies so it remains valide.
auto PA = PreservedAnalyses::allInSet<AllAnalysesOn<Function>>();
PA.preserve<FunctionAnalysisManagerCGSCCProxy>();
AM.invalidate(*C, PA);
}
auto NewSCCIndex = RC->find(*C) - RC->begin();
// If we have actually moved an SCC to be topologically "below" the current
// one due to merging, we will need to revisit the current SCC after
// visiting those moved SCCs.
//
// It is critical that we *do not* revisit the current SCC unless we
// actually move SCCs in the process of merging because otherwise we may
// form a cycle where an SCC is split apart, merged, split, merged and so
// on infinitely.
if (InitialSCCIndex < NewSCCIndex) {
// Put our current SCC back onto the worklist as we'll visit other SCCs
// that are now definitively ordered prior to the current one in the
// post-order sequence, and may end up observing more precise context to
// optimize the current SCC.
UR.CWorklist.insert(C);
LLVM_DEBUG(dbgs() << "Enqueuing the existing SCC in the worklist: " << *C
<< "\n");
// Enqueue in reverse order as we pop off the back of the worklist.
for (SCC &MovedC : llvm::reverse(make_range(RC->begin() + InitialSCCIndex,
RC->begin() + NewSCCIndex))) {
UR.CWorklist.insert(&MovedC);
LLVM_DEBUG(dbgs() << "Enqueuing a newly earlier in post-order SCC: "
<< MovedC << "\n");
}
}
}
assert(!UR.InvalidatedSCCs.count(C) && "Invalidated the current SCC!");
assert(!UR.InvalidatedRefSCCs.count(RC) && "Invalidated the current RefSCC!");
assert(&C->getOuterRefSCC() == RC && "Current SCC not in current RefSCC!");
// Record the current SCC for higher layers of the CGSCC pass manager now that
// all the updates have been applied.
if (C != &InitialC)
UR.UpdatedC = C;
return *C;
}
LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForFunctionPass(
LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
FunctionAnalysisManager &FAM) {
return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
/* FunctionPass */ true);
}
LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForCGSCCPass(
LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
FunctionAnalysisManager &FAM) {
return updateCGAndAnalysisManagerForPass(G, InitialC, N, AM, UR, FAM,
/* FunctionPass */ false);
}