llvm-mirror/lib/Analysis/CGSCCPassManager.cpp
Chandler Carruth 99ebb6e7dc [PM] Introduce the facilities for registering cross-IR-unit dependencies
that require deferred invalidation.

This handles the other real-world invalidation scenario that we have
cases of: a function analysis which caches references to a module
analysis. We currently do this in the AA aggregation layer and might
well do this in other places as well.

Since this is relative rare, the technique is somewhat more cumbersome.
Analyses need to register themselves when accessing the outer analysis
manager's proxy. This proxy is already necessarily present to allow
access to the outer IR unit's analyses. By registering here we can track
and trigger invalidation when that outer analysis goes away.

To make this work we need to enhance the PreservedAnalyses
infrastructure to support a (slightly) more explicit model for "sets" of
analyses, and allow abandoning a single specific analyses even when
a set covering that analysis is preserved. That allows us to describe
the scenario of preserving all Function analyses *except* for the one
where deferred invalidation has triggered.

We also need to teach the invalidator API to support direct ID calls
instead of always going through a template to dispatch so that we can
just record the ID mapping.

I've introduced testing of all of this both for simple module<->function
cases as well as for more complex cases involving a CGSCC layer.

Much like the previous patch I've not tried to fully update the loop
pass management layer because that layer is due to be heavily reworked
to use similar techniques to the CGSCC to handle updates. As that
happens, we'll have a better testing basis for adding support like this.

Many thanks to both Justin and Sean for the extensive reviews on this to
help bring the API design and documentation into a better state.

Differential Revision: https://reviews.llvm.org/D27198

llvm-svn: 290594
2016-12-27 08:40:39 +00:00

487 lines
20 KiB
C++

//===- CGSCCPassManager.cpp - Managing & running CGSCC passes -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/CGSCCPassManager.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/InstIterator.h"
using namespace llvm;
// Explicit template instantiations and specialization defininitions for core
// template typedefs.
namespace llvm {
// 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) {
PreservedAnalyses PA = PreservedAnalyses::all();
if (DebugLogging)
dbgs() << "Starting CGSCC pass manager run.\n";
// 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;
for (auto &Pass : Passes) {
if (DebugLogging)
dbgs() << "Running pass: " << Pass->name() << " on " << *C << "\n";
PreservedAnalyses PassPA = Pass->run(*C, AM, G, UR);
// Update the SCC if necessary.
C = UR.UpdatedC ? UR.UpdatedC : C;
// Check that we didn't miss any update scenario.
assert(!UR.InvalidatedSCCs.count(C) && "Processing an invalid SCC!");
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);
// Finally, we intersect the final preserved analyses to compute the
// aggregate preserved set for this pass manager.
PA.intersect(std::move(PassPA));
// FIXME: Historically, the pass managers all called the LLVM context's
// yield function here. We don't have a generic way to acquire the
// context and it isn't yet clear what the right pattern is for yielding
// in the new pass manager so it is currently omitted.
// ...getContext().yield();
}
// Invaliadtion 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>>();
if (DebugLogging)
dbgs() << "Finished CGSCC pass manager run.\n";
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.
for (auto &RC : G->postorder_ref_sccs())
for (auto &C : RC) {
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) {
// Collect the FunctionAnalysisManager from the Module layer and use that to
// build the proxy result.
//
// This allows us to rely on the FunctionAnalysisMangaerModuleProxy to
// invalidate the function analyses.
auto &MAM = AM.getResult<ModuleAnalysisManagerCGSCCProxy>(C, CG).getManager();
Module &M = *C.begin()->getFunction().getParent();
auto *FAMProxy = MAM.getCachedResult<FunctionAnalysisManagerModuleProxy>(M);
assert(FAMProxy && "The CGSCC pass manager requires that the FAM module "
"proxy is run on the module prior to entering the CGSCC "
"walk.");
// Note that we special-case invalidation handling of this proxy in the CGSCC
// analysis manager's Module proxy. This avoids the need to do anything
// special here to recompute all of this if ever the FAM's module proxy goes
// away.
return Result(FAMProxy->getManager());
}
bool FunctionAnalysisManagerCGSCCProxy::Result::invalidate(
LazyCallGraph::SCC &C, const PreservedAnalyses &PA,
CGSCCAnalysisManager::Invalidator &Inv) {
for (LazyCallGraph::Node &N : C)
FAM->invalidate(N.getFunction(), PA);
// This proxy doesn't need to handle invalidation itself. Instead, the
// module-level CGSCC proxy handles it above by ensuring that if the
// module-level FAM proxy becomes invalid the entire SCC layer, which
// includes this proxy, is cleared.
return false;
}
} // End llvm namespace
namespace {
/// 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>
LazyCallGraph::SCC *
incorporateNewSCCRange(const SCCRangeT &NewSCCRange, LazyCallGraph &G,
LazyCallGraph::Node &N, LazyCallGraph::SCC *C,
CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR,
bool DebugLogging = false) {
typedef LazyCallGraph::SCC SCC;
if (NewSCCRange.begin() == NewSCCRange.end())
return C;
// Invalidate the analyses of the current SCC and add it to the worklist since
// it has changed its shape.
AM.invalidate(*C, PreservedAnalyses::none());
UR.CWorklist.insert(C);
if (DebugLogging)
dbgs() << "Enqueuing the existing SCC in the worklist:" << *C << "\n";
SCC *OldC = C;
(void)OldC;
// 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!");
for (SCC &NewC :
reverse(make_range(std::next(NewSCCRange.begin()), NewSCCRange.end()))) {
assert(C != &NewC && "No need to re-visit the current SCC!");
assert(OldC != &NewC && "Already handled the original SCC!");
UR.CWorklist.insert(&NewC);
if (DebugLogging)
dbgs() << "Enqueuing a newly formed SCC:" << NewC << "\n";
}
return C;
}
}
LazyCallGraph::SCC &llvm::updateCGAndAnalysisManagerForFunctionPass(
LazyCallGraph &G, LazyCallGraph::SCC &InitialC, LazyCallGraph::Node &N,
CGSCCAnalysisManager &AM, CGSCCUpdateResult &UR, bool DebugLogging) {
typedef LazyCallGraph::Node Node;
typedef LazyCallGraph::Edge Edge;
typedef LazyCallGraph::SCC SCC;
typedef LazyCallGraph::RefSCC 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<Function *, 16> RetainedEdges;
SmallSetVector<Function *, 4> PromotedRefTargets;
SmallSetVector<Function *, 4> DemotedCallTargets;
// 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 CS = CallSite(&I))
if (Function *Callee = CS.getCalledFunction())
if (Visited.insert(Callee).second && !Callee->isDeclaration()) {
const Edge *E = N.lookup(*Callee);
// FIXME: We should really handle adding new calls. While it will
// make downstream usage more complex, there is no fundamental
// limitation and it will allow passes within the CGSCC to be a bit
// more flexible in what transforms they can do. Until then, we
// verify that new calls haven't been introduced.
assert(E && "No function transformations should introduce *new* "
"call edges! Any new calls should be modeled as "
"promoted existing ref edges!");
RetainedEdges.insert(Callee);
if (!E->isCall())
PromotedRefTargets.insert(Callee);
}
// Now walk all references.
for (Instruction &I : instructions(F))
for (Value *Op : I.operand_values())
if (Constant *C = dyn_cast<Constant>(Op))
if (Visited.insert(C).second)
Worklist.push_back(C);
LazyCallGraph::visitReferences(Worklist, Visited, [&](Function &Referee) {
const Edge *E = N.lookup(Referee);
// FIXME: Similarly to new calls, we also currently preclude
// introducing new references. See above for details.
assert(E && "No function transformations should introduce *new* ref "
"edges! Any new ref edges would require IPO which "
"function passes aren't allowed to do!");
RetainedEdges.insert(&Referee);
if (E->isCall())
DemotedCallTargets.insert(&Referee);
});
// First remove all of the edges that are no longer present in this function.
// We have to build a list of dead targets first and then remove them as the
// data structures will all be invalidated by removing them.
SmallVector<PointerIntPair<Node *, 1, Edge::Kind>, 4> DeadTargets;
for (Edge &E : N)
if (!RetainedEdges.count(&E.getFunction()))
DeadTargets.push_back({E.getNode(), E.getKind()});
for (auto DeadTarget : DeadTargets) {
Node &TargetN = *DeadTarget.getPointer();
bool IsCall = DeadTarget.getInt() == Edge::Call;
SCC &TargetC = *G.lookupSCC(TargetN);
RefSCC &TargetRC = TargetC.getOuterRefSCC();
if (&TargetRC != RC) {
RC->removeOutgoingEdge(N, TargetN);
if (DebugLogging)
dbgs() << "Deleting outgoing edge from '" << N << "' to '" << TargetN
<< "'\n";
continue;
}
if (DebugLogging)
dbgs() << "Deleting internal " << (IsCall ? "call" : "ref")
<< " edge from '" << N << "' to '" << TargetN << "'\n";
if (IsCall)
C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, TargetN), G, N,
C, AM, UR, DebugLogging);
auto NewRefSCCs = RC->removeInternalRefEdge(N, TargetN);
if (!NewRefSCCs.empty()) {
// 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.
// The RC worklist is in reverse postorder, so we first enqueue the
// current RefSCC as it will remain the parent of all split RefSCCs, then
// 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.
UR.RCWorklist.insert(RC);
if (DebugLogging)
dbgs() << "Enqueuing the existing RefSCC in the update worklist: "
<< *RC << "\n";
// Update the 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!");
assert(NewRefSCCs.front() == RC &&
"New current RefSCC not first in the returned list!");
for (RefSCC *NewRC : reverse(
make_range(std::next(NewRefSCCs.begin()), NewRefSCCs.end()))) {
assert(NewRC != RC && "Should not encounter the current RefSCC further "
"in the postorder list of new RefSCCs.");
UR.RCWorklist.insert(NewRC);
if (DebugLogging)
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 (Function *RefTarget : DemotedCallTargets) {
Node &TargetN = *G.lookup(*RefTarget);
SCC &TargetC = *G.lookupSCC(TargetN);
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) {
assert(RC->isAncestorOf(TargetRC) &&
"Cannot potentially form RefSCC cycles here!");
RC->switchOutgoingEdgeToRef(N, TargetN);
if (DebugLogging)
dbgs() << "Switch outgoing call edge to a ref edge from '" << N
<< "' to '" << TargetN << "'\n";
continue;
}
// Otherwise we are switching an internal call edge to a ref edge. This
// may split up some SCCs.
C = incorporateNewSCCRange(RC->switchInternalEdgeToRef(N, TargetN), G, N, C,
AM, UR, DebugLogging);
}
// Now promote ref edges into call edges.
for (Function *CallTarget : PromotedRefTargets) {
Node &TargetN = *G.lookup(*CallTarget);
SCC &TargetC = *G.lookupSCC(TargetN);
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) {
assert(RC->isAncestorOf(TargetRC) &&
"Cannot potentially form RefSCC cycles here!");
RC->switchOutgoingEdgeToCall(N, TargetN);
if (DebugLogging)
dbgs() << "Switch outgoing ref edge to a call edge from '" << N
<< "' to '" << TargetN << "'\n";
continue;
}
if (DebugLogging)
dbgs() << "Switch an internal ref edge to a call edge from '" << N
<< "' to '" << TargetN << "'\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.
auto InitialSCCIndex = RC->find(*C) - RC->begin();
auto InvalidatedSCCs = RC->switchInternalEdgeToCall(N, TargetN);
if (!InvalidatedSCCs.empty()) {
C = &TargetC;
assert(G.lookupSCC(N) == C && "Failed to update current SCC!");
// Any analyses cached for this SCC are no longer precise as the shape
// has changed by introducing this cycle.
AM.invalidate(*C, PreservedAnalyses::none());
for (SCC *InvalidatedC : InvalidatedSCCs) {
assert(InvalidatedC != C && "Cannot invalidate the current SCC!");
UR.InvalidatedSCCs.insert(InvalidatedC);
// Also clear any cached analyses for the SCCs that are dead. This
// isn't really necessary for correctness but can release memory.
AM.clear(*InvalidatedC);
}
}
auto NewSCCIndex = RC->find(*C) - RC->begin();
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);
if (DebugLogging)
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 : reverse(make_range(RC->begin() + InitialSCCIndex,
RC->begin() + NewSCCIndex))) {
UR.CWorklist.insert(&MovedC);
if (DebugLogging)
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 RefSCC and SCC for higher layers of the CGSCC pass
// manager now that all the updates have been applied.
if (RC != &InitialRC)
UR.UpdatedRC = RC;
if (C != &InitialC)
UR.UpdatedC = C;
return *C;
}