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98c14daece
llvm-mirror/lib/Transforms/IPO/Inliner.cpp
Chandler Carruth 98c14daece [PM] Fix a really nasty bug introduced when adding PGO support to the 
new PM's inliner.

The bug happens when we refine an SCC after having computed a proxy for
the FunctionAnalysisManager, and then proceed to compute fresh analyses
for functions in the *new* SCC using the manager provided by the old
SCC's proxy. *And* when we manage to mutate a function in this new SCC
in a way that invalidates those analyses. This can be... challenging to
reproduce.

I've managed to contrive a set of functions that trigger this and added
a test case, but it is a bit brittle. I've directly checked that the
passes run in the expected ways to help avoid the test just becoming
silently irrelevant.

This gets the new PM back to passing the LLVM test suite after the PGO
improvements landed.

llvm-svn: 292757
2017-01-22 10:34:01 +00:00

956 lines
40 KiB
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//===- Inliner.cpp - Code common to all inliners --------------------------===//
//
// 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 mechanics required to implement inlining without
// missing any calls and updating the call graph. The decisions of which calls
// are profitable to inline are implemented elsewhere.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO/Inliner.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BasicAliasAnalysis.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/InlineCost.h"
#include "llvm/Analysis/OptimizationDiagnosticInfo.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
#define DEBUG_TYPE "inline"
STATISTIC(NumInlined, "Number of functions inlined");
STATISTIC(NumCallsDeleted, "Number of call sites deleted, not inlined");
STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
STATISTIC(NumMergedAllocas, "Number of allocas merged together");
// This weirdly named statistic tracks the number of times that, when attempting
// to inline a function A into B, we analyze the callers of B in order to see
// if those would be more profitable and blocked inline steps.
STATISTIC(NumCallerCallersAnalyzed, "Number of caller-callers analyzed");
/// Flag to disable manual alloca merging.
///
/// Merging of allocas was originally done as a stack-size saving technique
/// prior to LLVM's code generator having support for stack coloring based on
/// lifetime markers. It is now in the process of being removed. To experiment
/// with disabling it and relying fully on lifetime marker based stack
/// coloring, you can pass this flag to LLVM.
static cl::opt<bool>
DisableInlinedAllocaMerging("disable-inlined-alloca-merging",
cl::init(false), cl::Hidden);
namespace {
enum class InlinerFunctionImportStatsOpts {
No = 0,
Basic = 1,
Verbose = 2,
};
cl::opt<InlinerFunctionImportStatsOpts> InlinerFunctionImportStats(
"inliner-function-import-stats",
cl::init(InlinerFunctionImportStatsOpts::No),
cl::values(clEnumValN(InlinerFunctionImportStatsOpts::Basic, "basic",
"basic statistics"),
clEnumValN(InlinerFunctionImportStatsOpts::Verbose, "verbose",
"printing of statistics for each inlined function")),
cl::Hidden, cl::desc("Enable inliner stats for imported functions"));
} // namespace
LegacyInlinerBase::LegacyInlinerBase(char &ID)
: CallGraphSCCPass(ID), InsertLifetime(true) {}
LegacyInlinerBase::LegacyInlinerBase(char &ID, bool InsertLifetime)
: CallGraphSCCPass(ID), InsertLifetime(InsertLifetime) {}
/// 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 LegacyInlinerBase::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<ProfileSummaryInfoWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
getAAResultsAnalysisUsage(AU);
CallGraphSCCPass::getAnalysisUsage(AU);
}
typedef DenseMap<ArrayType *, std::vector<AllocaInst *>> InlinedArrayAllocasTy;
/// Look at all of the allocas that we inlined through this call site. If we
/// have already inlined other allocas through other calls into this function,
/// then we know that they have disjoint lifetimes and that we can merge them.
///
/// There are many heuristics possible for merging these allocas, and the
/// different options have different tradeoffs. One thing that we *really*
/// don't want to hurt is SRoA: once inlining happens, often allocas are no
/// longer address taken and so they can be promoted.
///
/// Our "solution" for that is to only merge allocas whose outermost type is an
/// array type. These are usually not promoted because someone is using a
/// variable index into them. These are also often the most important ones to
/// merge.
///
/// A better solution would be to have real memory lifetime markers in the IR
/// and not have the inliner do any merging of allocas at all. This would
/// allow the backend to do proper stack slot coloring of all allocas that
/// *actually make it to the backend*, which is really what we want.
///
/// Because we don't have this information, we do this simple and useful hack.
static void mergeInlinedArrayAllocas(
Function *Caller, InlineFunctionInfo &IFI,
InlinedArrayAllocasTy &InlinedArrayAllocas, int InlineHistory) {
SmallPtrSet<AllocaInst *, 16> UsedAllocas;
// When processing our SCC, check to see if CS was inlined from some other
// call site. For example, if we're processing "A" in this code:
// A() { B() }
// B() { x = alloca ... C() }
// C() { y = alloca ... }
// Assume that C was not inlined into B initially, and so we're processing A
// and decide to inline B into A. Doing this makes an alloca available for
// reuse and makes a callsite (C) available for inlining. When we process
// the C call site we don't want to do any alloca merging between X and Y
// because their scopes are not disjoint. We could make this smarter by
// keeping track of the inline history for each alloca in the
// InlinedArrayAllocas but this isn't likely to be a significant win.
if (InlineHistory != -1) // Only do merging for top-level call sites in SCC.
return;
// Loop over all the allocas we have so far and see if they can be merged with
// a previously inlined alloca. If not, remember that we had it.
for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size(); AllocaNo != e;
++AllocaNo) {
AllocaInst *AI = IFI.StaticAllocas[AllocaNo];
// Don't bother trying to merge array allocations (they will usually be
// canonicalized to be an allocation *of* an array), or allocations whose
// type is not itself an array (because we're afraid of pessimizing SRoA).
ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
if (!ATy || AI->isArrayAllocation())
continue;
// Get the list of all available allocas for this array type.
std::vector<AllocaInst *> &AllocasForType = InlinedArrayAllocas[ATy];
// Loop over the allocas in AllocasForType to see if we can reuse one. Note
// that we have to be careful not to reuse the same "available" alloca for
// multiple different allocas that we just inlined, we use the 'UsedAllocas'
// set to keep track of which "available" allocas are being used by this
// function. Also, AllocasForType can be empty of course!
bool MergedAwayAlloca = false;
for (AllocaInst *AvailableAlloca : AllocasForType) {
unsigned Align1 = AI->getAlignment(),
Align2 = AvailableAlloca->getAlignment();
// The available alloca has to be in the right function, not in some other
// function in this SCC.
if (AvailableAlloca->getParent() != AI->getParent())
continue;
// If the inlined function already uses this alloca then we can't reuse
// it.
if (!UsedAllocas.insert(AvailableAlloca).second)
continue;
// Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
// success!
DEBUG(dbgs() << " ***MERGED ALLOCA: " << *AI
<< "\n\t\tINTO: " << *AvailableAlloca << '\n');
// Move affected dbg.declare calls immediately after the new alloca to
// avoid the situation when a dbg.declare precedes its alloca.
if (auto *L = LocalAsMetadata::getIfExists(AI))
if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L))
for (User *U : MDV->users())
if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
DDI->moveBefore(AvailableAlloca->getNextNode());
AI->replaceAllUsesWith(AvailableAlloca);
if (Align1 != Align2) {
if (!Align1 || !Align2) {
const DataLayout &DL = Caller->getParent()->getDataLayout();
unsigned TypeAlign = DL.getABITypeAlignment(AI->getAllocatedType());
Align1 = Align1 ? Align1 : TypeAlign;
Align2 = Align2 ? Align2 : TypeAlign;
}
if (Align1 > Align2)
AvailableAlloca->setAlignment(AI->getAlignment());
}
AI->eraseFromParent();
MergedAwayAlloca = true;
++NumMergedAllocas;
IFI.StaticAllocas[AllocaNo] = nullptr;
break;
}
// If we already nuked the alloca, we're done with it.
if (MergedAwayAlloca)
continue;
// If we were unable to merge away the alloca either because there are no
// allocas of the right type available or because we reused them all
// already, remember that this alloca came from an inlined function and mark
// it used so we don't reuse it for other allocas from this inline
// operation.
AllocasForType.push_back(AI);
UsedAllocas.insert(AI);
}
}
/// If it is possible to inline the specified call site,
/// do so and update the CallGraph for this operation.
///
/// This function also does some basic book-keeping to update the IR. The
/// InlinedArrayAllocas map keeps track of any allocas that are already
/// available from other functions inlined into the caller. If we are able to
/// inline this call site we attempt to reuse already available allocas or add
/// any new allocas to the set if not possible.
static bool InlineCallIfPossible(
CallSite CS, InlineFunctionInfo &IFI,
InlinedArrayAllocasTy &InlinedArrayAllocas, int InlineHistory,
bool InsertLifetime, function_ref<AAResults &(Function &)> &AARGetter,
ImportedFunctionsInliningStatistics &ImportedFunctionsStats) {
Function *Callee = CS.getCalledFunction();
Function *Caller = CS.getCaller();
AAResults &AAR = AARGetter(*Callee);
// Try to inline the function. Get the list of static allocas that were
// inlined.
if (!InlineFunction(CS, IFI, &AAR, InsertLifetime))
return false;
if (InlinerFunctionImportStats != InlinerFunctionImportStatsOpts::No)
ImportedFunctionsStats.recordInline(*Caller, *Callee);
AttributeFuncs::mergeAttributesForInlining(*Caller, *Callee);
if (!DisableInlinedAllocaMerging)
mergeInlinedArrayAllocas(Caller, IFI, InlinedArrayAllocas, InlineHistory);
return true;
}
/// Return true if inlining of CS can block the caller from being
/// inlined which is proved to be more beneficial. \p IC is the
/// estimated inline cost associated with callsite \p CS.
/// \p TotalAltCost will be set to the estimated cost of inlining the caller
/// if \p CS is suppressed for inlining.
static bool
shouldBeDeferred(Function *Caller, CallSite CS, InlineCost IC,
int &TotalSecondaryCost,
function_ref<InlineCost(CallSite CS)> GetInlineCost) {
// For now we only handle local or inline functions.
if (!Caller->hasLocalLinkage() && !Caller->hasLinkOnceODRLinkage())
return false;
// Try to detect the case where the current inlining candidate caller (call
// it B) is a static or linkonce-ODR function and is an inlining candidate
// elsewhere, and the current candidate callee (call it C) is large enough
// that inlining it into B would make B too big to inline later. In these
// circumstances it may be best not to inline C into B, but to inline B into
// its callers.
//
// This only applies to static and linkonce-ODR functions because those are
// expected to be available for inlining in the translation units where they
// are used. Thus we will always have the opportunity to make local inlining
// decisions. Importantly the linkonce-ODR linkage covers inline functions
// and templates in C++.
//
// FIXME: All of this logic should be sunk into getInlineCost. It relies on
// the internal implementation of the inline cost metrics rather than
// treating them as truly abstract units etc.
TotalSecondaryCost = 0;
// The candidate cost to be imposed upon the current function.
int CandidateCost = IC.getCost() - (InlineConstants::CallPenalty + 1);
// This bool tracks what happens if we do NOT inline C into B.
bool callerWillBeRemoved = Caller->hasLocalLinkage();
// This bool tracks what happens if we DO inline C into B.
bool inliningPreventsSomeOuterInline = false;
for (User *U : Caller->users()) {
CallSite CS2(U);
// If this isn't a call to Caller (it could be some other sort
// of reference) skip it. Such references will prevent the caller
// from being removed.
if (!CS2 || CS2.getCalledFunction() != Caller) {
callerWillBeRemoved = false;
continue;
}
InlineCost IC2 = GetInlineCost(CS2);
++NumCallerCallersAnalyzed;
if (!IC2) {
callerWillBeRemoved = false;
continue;
}
if (IC2.isAlways())
continue;
// See if inlining of the original callsite would erase the cost delta of
// this callsite. We subtract off the penalty for the call instruction,
// which we would be deleting.
if (IC2.getCostDelta() <= CandidateCost) {
inliningPreventsSomeOuterInline = true;
TotalSecondaryCost += IC2.getCost();
}
}
// If all outer calls to Caller would get inlined, the cost for the last
// one is set very low by getInlineCost, in anticipation that Caller will
// be removed entirely. We did not account for this above unless there
// is only one caller of Caller.
if (callerWillBeRemoved && !Caller->use_empty())
TotalSecondaryCost -= InlineConstants::LastCallToStaticBonus;
if (inliningPreventsSomeOuterInline && TotalSecondaryCost < IC.getCost())
return true;
return false;
}
/// Return true if the inliner should attempt to inline at the given CallSite.
static bool shouldInline(CallSite CS,
function_ref<InlineCost(CallSite CS)> GetInlineCost,
OptimizationRemarkEmitter &ORE) {
using namespace ore;
InlineCost IC = GetInlineCost(CS);
Instruction *Call = CS.getInstruction();
Function *Callee = CS.getCalledFunction();
if (IC.isAlways()) {
DEBUG(dbgs() << " Inlining: cost=always"
<< ", Call: " << *CS.getInstruction() << "\n");
ORE.emit(OptimizationRemarkAnalysis(DEBUG_TYPE, "AlwaysInline", Call)
<< NV("Callee", Callee)
<< " should always be inlined (cost=always)");
return true;
}
if (IC.isNever()) {
DEBUG(dbgs() << " NOT Inlining: cost=never"
<< ", Call: " << *CS.getInstruction() << "\n");
ORE.emit(OptimizationRemarkAnalysis(DEBUG_TYPE, "NeverInline", Call)
<< NV("Callee", Callee)
<< " should never be inlined (cost=never)");
return false;
}
Function *Caller = CS.getCaller();
if (!IC) {
DEBUG(dbgs() << " NOT Inlining: cost=" << IC.getCost()
<< ", thres=" << (IC.getCostDelta() + IC.getCost())
<< ", Call: " << *CS.getInstruction() << "\n");
ORE.emit(OptimizationRemarkAnalysis(DEBUG_TYPE, "TooCostly", Call)
<< NV("Callee", Callee) << " too costly to inline (cost="
<< NV("Cost", IC.getCost()) << ", threshold="
<< NV("Threshold", IC.getCostDelta() + IC.getCost()) << ")");
return false;
}
int TotalSecondaryCost = 0;
if (shouldBeDeferred(Caller, CS, IC, TotalSecondaryCost, GetInlineCost)) {
DEBUG(dbgs() << " NOT Inlining: " << *CS.getInstruction()
<< " Cost = " << IC.getCost()
<< ", outer Cost = " << TotalSecondaryCost << '\n');
ORE.emit(OptimizationRemarkAnalysis(DEBUG_TYPE,
"IncreaseCostInOtherContexts", Call)
<< "Not inlining. Cost of inlining " << NV("Callee", Callee)
<< " increases the cost of inlining " << NV("Caller", Caller)
<< " in other contexts");
return false;
}
DEBUG(dbgs() << " Inlining: cost=" << IC.getCost()
<< ", thres=" << (IC.getCostDelta() + IC.getCost())
<< ", Call: " << *CS.getInstruction() << '\n');
ORE.emit(OptimizationRemarkAnalysis(DEBUG_TYPE, "CanBeInlined", Call)
<< NV("Callee", Callee) << " can be inlined into "
<< NV("Caller", Caller) << " with cost=" << NV("Cost", IC.getCost())
<< " (threshold="
<< NV("Threshold", IC.getCostDelta() + IC.getCost()) << ")");
return true;
}
/// Return true if the specified inline history ID
/// indicates an inline history that includes the specified function.
static bool InlineHistoryIncludes(
Function *F, int InlineHistoryID,
const SmallVectorImpl<std::pair<Function *, int>> &InlineHistory) {
while (InlineHistoryID != -1) {
assert(unsigned(InlineHistoryID) < InlineHistory.size() &&
"Invalid inline history ID");
if (InlineHistory[InlineHistoryID].first == F)
return true;
InlineHistoryID = InlineHistory[InlineHistoryID].second;
}
return false;
}
bool LegacyInlinerBase::doInitialization(CallGraph &CG) {
if (InlinerFunctionImportStats != InlinerFunctionImportStatsOpts::No)
ImportedFunctionsStats.setModuleInfo(CG.getModule());
return false; // No changes to CallGraph.
}
bool LegacyInlinerBase::runOnSCC(CallGraphSCC &SCC) {
if (skipSCC(SCC))
return false;
return inlineCalls(SCC);
}
static bool
inlineCallsImpl(CallGraphSCC &SCC, CallGraph &CG,
std::function<AssumptionCache &(Function &)> GetAssumptionCache,
ProfileSummaryInfo *PSI, TargetLibraryInfo &TLI,
bool InsertLifetime,
function_ref<InlineCost(CallSite CS)> GetInlineCost,
function_ref<AAResults &(Function &)> AARGetter,
ImportedFunctionsInliningStatistics &ImportedFunctionsStats) {
SmallPtrSet<Function *, 8> SCCFunctions;
DEBUG(dbgs() << "Inliner visiting SCC:");
for (CallGraphNode *Node : SCC) {
Function *F = Node->getFunction();
if (F)
SCCFunctions.insert(F);
DEBUG(dbgs() << " " << (F ? F->getName() : "INDIRECTNODE"));
}
// Scan through and identify all call sites ahead of time so that we only
// inline call sites in the original functions, not call sites that result
// from inlining other functions.
SmallVector<std::pair<CallSite, int>, 16> CallSites;
// When inlining a callee produces new call sites, we want to keep track of
// the fact that they were inlined from the callee. This allows us to avoid
// infinite inlining in some obscure cases. To represent this, we use an
// index into the InlineHistory vector.
SmallVector<std::pair<Function *, int>, 8> InlineHistory;
for (CallGraphNode *Node : SCC) {
Function *F = Node->getFunction();
if (!F || F->isDeclaration())
continue;
OptimizationRemarkEmitter ORE(F);
for (BasicBlock &BB : *F)
for (Instruction &I : BB) {
CallSite CS(cast<Value>(&I));
// If this isn't a call, or it is a call to an intrinsic, it can
// never be inlined.
if (!CS || isa<IntrinsicInst>(I))
continue;
// If this is a direct call to an external function, we can never inline
// it. If it is an indirect call, inlining may resolve it to be a
// direct call, so we keep it.
if (Function *Callee = CS.getCalledFunction())
if (Callee->isDeclaration()) {
using namespace ore;
ORE.emit(OptimizationRemarkMissed(DEBUG_TYPE, "NoDefinition", &I)
<< NV("Callee", Callee) << " will not be inlined into "
<< NV("Caller", CS.getCaller())
<< " because its definition is unavailable"
<< setIsVerbose());
continue;
}
CallSites.push_back(std::make_pair(CS, -1));
}
}
DEBUG(dbgs() << ": " << CallSites.size() << " call sites.\n");
// If there are no calls in this function, exit early.
if (CallSites.empty())
return false;
// Now that we have all of the call sites, move the ones to functions in the
// current SCC to the end of the list.
unsigned FirstCallInSCC = CallSites.size();
for (unsigned i = 0; i < FirstCallInSCC; ++i)
if (Function *F = CallSites[i].first.getCalledFunction())
if (SCCFunctions.count(F))
std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
InlinedArrayAllocasTy InlinedArrayAllocas;
InlineFunctionInfo InlineInfo(&CG, &GetAssumptionCache);
// Now that we have all of the call sites, loop over them and inline them if
// it looks profitable to do so.
bool Changed = false;
bool LocalChange;
do {
LocalChange = false;
// Iterate over the outer loop because inlining functions can cause indirect
// calls to become direct calls.
// CallSites may be modified inside so ranged for loop can not be used.
for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
CallSite CS = CallSites[CSi].first;
Function *Caller = CS.getCaller();
Function *Callee = CS.getCalledFunction();
// If this call site is dead and it is to a readonly function, we should
// just delete the call instead of trying to inline it, regardless of
// size. This happens because IPSCCP propagates the result out of the
// call and then we're left with the dead call.
if (isInstructionTriviallyDead(CS.getInstruction(), &TLI)) {
DEBUG(dbgs() << " -> Deleting dead call: " << *CS.getInstruction()
<< "\n");
// Update the call graph by deleting the edge from Callee to Caller.
CG[Caller]->removeCallEdgeFor(CS);
CS.getInstruction()->eraseFromParent();
++NumCallsDeleted;
} else {
// We can only inline direct calls to non-declarations.
if (!Callee || Callee->isDeclaration())
continue;
// If this call site was obtained by inlining another function, verify
// that the include path for the function did not include the callee
// itself. If so, we'd be recursively inlining the same function,
// which would provide the same callsites, which would cause us to
// infinitely inline.
int InlineHistoryID = CallSites[CSi].second;
if (InlineHistoryID != -1 &&
InlineHistoryIncludes(Callee, InlineHistoryID, InlineHistory))
continue;
// Get DebugLoc to report. CS will be invalid after Inliner.
DebugLoc DLoc = CS.getInstruction()->getDebugLoc();
BasicBlock *Block = CS.getParent();
// FIXME for new PM: because of the old PM we currently generate ORE and
// in turn BFI on demand. With the new PM, the ORE dependency should
// just become a regular analysis dependency.
OptimizationRemarkEmitter ORE(Caller);
// If the policy determines that we should inline this function,
// try to do so.
using namespace ore;
if (!shouldInline(CS, GetInlineCost, ORE)) {
ORE.emit(
OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc, Block)
<< NV("Callee", Callee) << " will not be inlined into "
<< NV("Caller", Caller));
continue;
}
// Attempt to inline the function.
if (!InlineCallIfPossible(CS, InlineInfo, InlinedArrayAllocas,
InlineHistoryID, InsertLifetime, AARGetter,
ImportedFunctionsStats)) {
ORE.emit(
OptimizationRemarkMissed(DEBUG_TYPE, "NotInlined", DLoc, Block)
<< NV("Callee", Callee) << " will not be inlined into "
<< NV("Caller", Caller));
continue;
}
++NumInlined;
// Report the inline decision.
ORE.emit(OptimizationRemark(DEBUG_TYPE, "Inlined", DLoc, Block)
<< NV("Callee", Callee) << " inlined into "
<< NV("Caller", Caller));
// If inlining this function gave us any new call sites, throw them
// onto our worklist to process. They are useful inline candidates.
if (!InlineInfo.InlinedCalls.empty()) {
// Create a new inline history entry for this, so that we remember
// that these new callsites came about due to inlining Callee.
int NewHistoryID = InlineHistory.size();
InlineHistory.push_back(std::make_pair(Callee, InlineHistoryID));
for (Value *Ptr : InlineInfo.InlinedCalls)
CallSites.push_back(std::make_pair(CallSite(Ptr), NewHistoryID));
}
}
// If we inlined or deleted the last possible call site to the function,
// delete the function body now.
if (Callee && Callee->use_empty() && Callee->hasLocalLinkage() &&
// TODO: Can remove if in SCC now.
!SCCFunctions.count(Callee) &&
// The function may be apparently dead, but if there are indirect
// callgraph references to the node, we cannot delete it yet, this
// could invalidate the CGSCC iterator.
CG[Callee]->getNumReferences() == 0) {
DEBUG(dbgs() << " -> Deleting dead function: " << Callee->getName()
<< "\n");
CallGraphNode *CalleeNode = CG[Callee];
// Remove any call graph edges from the callee to its callees.
CalleeNode->removeAllCalledFunctions();
// Removing the node for callee from the call graph and delete it.
delete CG.removeFunctionFromModule(CalleeNode);
++NumDeleted;
}
// Remove this call site from the list. If possible, use
// swap/pop_back for efficiency, but do not use it if doing so would
// move a call site to a function in this SCC before the
// 'FirstCallInSCC' barrier.
if (SCC.isSingular()) {
CallSites[CSi] = CallSites.back();
CallSites.pop_back();
} else {
CallSites.erase(CallSites.begin() + CSi);
}
--CSi;
Changed = true;
LocalChange = true;
}
} while (LocalChange);
return Changed;
}
bool LegacyInlinerBase::inlineCalls(CallGraphSCC &SCC) {
CallGraph &CG = getAnalysis<CallGraphWrapperPass>().getCallGraph();
ACT = &getAnalysis<AssumptionCacheTracker>();
PSI = getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
// We compute dedicated AA results for each function in the SCC as needed. We
// use a lambda referencing external objects so that they live long enough to
// be queried, but we re-use them each time.
Optional<BasicAAResult> BAR;
Optional<AAResults> AAR;
auto AARGetter = [&](Function &F) -> AAResults & {
BAR.emplace(createLegacyPMBasicAAResult(*this, F));
AAR.emplace(createLegacyPMAAResults(*this, F, *BAR));
return *AAR;
};
auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
return ACT->getAssumptionCache(F);
};
return inlineCallsImpl(SCC, CG, GetAssumptionCache, PSI, TLI, InsertLifetime,
[this](CallSite CS) { return getInlineCost(CS); },
AARGetter, ImportedFunctionsStats);
}
/// Remove now-dead linkonce functions at the end of
/// processing to avoid breaking the SCC traversal.
bool LegacyInlinerBase::doFinalization(CallGraph &CG) {
if (InlinerFunctionImportStats != InlinerFunctionImportStatsOpts::No)
ImportedFunctionsStats.dump(InlinerFunctionImportStats ==
InlinerFunctionImportStatsOpts::Verbose);
return removeDeadFunctions(CG);
}
/// Remove dead functions that are not included in DNR (Do Not Remove) list.
bool LegacyInlinerBase::removeDeadFunctions(CallGraph &CG,
bool AlwaysInlineOnly) {
SmallVector<CallGraphNode *, 16> FunctionsToRemove;
SmallVector<Function *, 16> DeadFunctionsInComdats;
auto RemoveCGN = [&](CallGraphNode *CGN) {
// Remove any call graph edges from the function to its callees.
CGN->removeAllCalledFunctions();
// Remove any edges from the external node to the function's call graph
// node. These edges might have been made irrelegant due to
// optimization of the program.
CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
// Removing the node for callee from the call graph and delete it.
FunctionsToRemove.push_back(CGN);
};
// Scan for all of the functions, looking for ones that should now be removed
// from the program. Insert the dead ones in the FunctionsToRemove set.
for (const auto &I : CG) {
CallGraphNode *CGN = I.second.get();
Function *F = CGN->getFunction();
if (!F || F->isDeclaration())
continue;
// Handle the case when this function is called and we only want to care
// about always-inline functions. This is a bit of a hack to share code
// between here and the InlineAlways pass.
if (AlwaysInlineOnly && !F->hasFnAttribute(Attribute::AlwaysInline))
continue;
// If the only remaining users of the function are dead constants, remove
// them.
F->removeDeadConstantUsers();
if (!F->isDefTriviallyDead())
continue;
// It is unsafe to drop a function with discardable linkage from a COMDAT
// without also dropping the other members of the COMDAT.
// The inliner doesn't visit non-function entities which are in COMDAT
// groups so it is unsafe to do so *unless* the linkage is local.
if (!F->hasLocalLinkage()) {
if (F->hasComdat()) {
DeadFunctionsInComdats.push_back(F);
continue;
}
}
RemoveCGN(CGN);
}
if (!DeadFunctionsInComdats.empty()) {
// Filter out the functions whose comdats remain alive.
filterDeadComdatFunctions(CG.getModule(), DeadFunctionsInComdats);
// Remove the rest.
for (Function *F : DeadFunctionsInComdats)
RemoveCGN(CG[F]);
}
if (FunctionsToRemove.empty())
return false;
// Now that we know which functions to delete, do so. We didn't want to do
// this inline, because that would invalidate our CallGraph::iterator
// objects. :(
//
// Note that it doesn't matter that we are iterating over a non-stable order
// here to do this, it doesn't matter which order the functions are deleted
// in.
array_pod_sort(FunctionsToRemove.begin(), FunctionsToRemove.end());
FunctionsToRemove.erase(
std::unique(FunctionsToRemove.begin(), FunctionsToRemove.end()),
FunctionsToRemove.end());
for (CallGraphNode *CGN : FunctionsToRemove) {
delete CG.removeFunctionFromModule(CGN);
++NumDeleted;
}
return true;
}
PreservedAnalyses InlinerPass::run(LazyCallGraph::SCC &InitialC,
CGSCCAnalysisManager &AM, LazyCallGraph &CG,
CGSCCUpdateResult &UR) {
const ModuleAnalysisManager &MAM =
AM.getResult<ModuleAnalysisManagerCGSCCProxy>(InitialC, CG).getManager();
bool Changed = false;
assert(InitialC.size() > 0 && "Cannot handle an empty SCC!");
Module &M = *InitialC.begin()->getFunction().getParent();
ProfileSummaryInfo *PSI = MAM.getCachedResult<ProfileSummaryAnalysis>(M);
// We use a worklist of nodes to process so that we can handle if the SCC
// structure changes and some nodes are no longer part of the current SCC. We
// also need to use an updatable pointer for the SCC as a consequence.
SmallVector<LazyCallGraph::Node *, 16> Nodes;
for (auto &N : InitialC)
Nodes.push_back(&N);
auto *C = &InitialC;
auto *RC = &C->getOuterRefSCC();
// We also use a secondary worklist of call sites within a particular node to
// allow quickly continuing to inline through newly inlined call sites where
// possible.
SmallVector<std::pair<CallSite, int>, 16> Calls;
// When inlining a callee produces new call sites, we want to keep track of
// the fact that they were inlined from the callee. This allows us to avoid
// infinite inlining in some obscure cases. To represent this, we use an
// index into the InlineHistory vector.
SmallVector<std::pair<Function *, int>, 16> InlineHistory;
// Track a set vector of inlined callees so that we can augment the caller
// with all of their edges in the call graph before pruning out the ones that
// got simplified away.
SmallSetVector<Function *, 4> InlinedCallees;
// Track the dead functions to delete once finished with inlining calls. We
// defer deleting these to make it easier to handle the call graph updates.
SmallVector<Function *, 4> DeadFunctions;
do {
auto &N = *Nodes.pop_back_val();
if (CG.lookupSCC(N) != C)
continue;
Function &F = N.getFunction();
if (F.hasFnAttribute(Attribute::OptimizeNone))
continue;
DEBUG(dbgs() << "Inlining calls in: " << F.getName() << "\n");
// Get a FunctionAnalysisManager via a proxy for this particular node. We
// do this each time we visit a node as the SCC may have changed and as
// we're going to mutate this particular function we want to make sure the
// proxy is in place to forward any invalidation events. We can use the
// manager we get here for looking up results for functions other than this
// node however because those functions aren't going to be mutated by this
// pass.
FunctionAnalysisManager &FAM =
AM.getResult<FunctionAnalysisManagerCGSCCProxy>(*C, CG)
.getManager();
std::function<AssumptionCache &(Function &)> GetAssumptionCache =
[&](Function &F) -> AssumptionCache & {
return FAM.getResult<AssumptionAnalysis>(F);
};
auto GetBFI = [&](Function &F) -> BlockFrequencyInfo & {
return FAM.getResult<BlockFrequencyAnalysis>(F);
};
auto GetInlineCost = [&](CallSite CS) {
Function &Callee = *CS.getCalledFunction();
auto &CalleeTTI = FAM.getResult<TargetIRAnalysis>(Callee);
return getInlineCost(CS, Params, CalleeTTI, GetAssumptionCache, {GetBFI},
PSI);
};
// Get the remarks emission analysis for the caller.
auto &ORE = FAM.getResult<OptimizationRemarkEmitterAnalysis>(F);
// We want to generally process call sites top-down in order for
// simplifications stemming from replacing the call with the returned value
// after inlining to be visible to subsequent inlining decisions. So we
// walk the function backwards and then process the back of the vector.
// FIXME: Using reverse is a really bad way to do this. Instead we should
// do an actual PO walk of the function body.
for (Instruction &I : reverse(instructions(F)))
if (auto CS = CallSite(&I))
if (Function *Callee = CS.getCalledFunction())
if (!Callee->isDeclaration())
Calls.push_back({CS, -1});
bool DidInline = false;
while (!Calls.empty()) {
int InlineHistoryID;
CallSite CS;
std::tie(CS, InlineHistoryID) = Calls.pop_back_val();
Function &Callee = *CS.getCalledFunction();
if (InlineHistoryID != -1 &&
InlineHistoryIncludes(&Callee, InlineHistoryID, InlineHistory))
continue;
// Check whether we want to inline this callsite.
if (!shouldInline(CS, GetInlineCost, ORE))
continue;
// Setup the data structure used to plumb customization into the
// `InlineFunction` routine.
InlineFunctionInfo IFI(
/*cg=*/nullptr, &GetAssumptionCache,
&FAM.getResult<BlockFrequencyAnalysis>(*(CS.getCaller())),
&FAM.getResult<BlockFrequencyAnalysis>(Callee));
if (!InlineFunction(CS, IFI))
continue;
DidInline = true;
InlinedCallees.insert(&Callee);
// Add any new callsites to defined functions to the worklist.
if (!IFI.InlinedCallSites.empty()) {
int NewHistoryID = InlineHistory.size();
InlineHistory.push_back({&Callee, InlineHistoryID});
for (CallSite &CS : reverse(IFI.InlinedCallSites))
if (Function *NewCallee = CS.getCalledFunction())
if (!NewCallee->isDeclaration())
Calls.push_back({CS, NewHistoryID});
}
// Merge the attributes based on the inlining.
AttributeFuncs::mergeAttributesForInlining(F, Callee);
// For local functions, check whether this makes the callee trivially
// dead. In that case, we can drop the body of the function eagerly
// which may reduce the number of callers of other functions to one,
// changing inline cost thresholds.
if (Callee.hasLocalLinkage()) {
// To check this we also need to nuke any dead constant uses (perhaps
// made dead by this operation on other functions).
Callee.removeDeadConstantUsers();
if (Callee.use_empty()) {
// Clear the body and queue the function itself for deletion when we
// finish inlining and call graph updates.
// Note that after this point, it is an error to do anything other
// than use the callee's address or delete it.
Callee.dropAllReferences();
assert(find(DeadFunctions, &Callee) == DeadFunctions.end() &&
"Cannot put cause a function to become dead twice!");
DeadFunctions.push_back(&Callee);
}
}
}
if (!DidInline)
continue;
Changed = true;
// Add all the inlined callees' edges as ref edges to the caller. These are
// by definition trivial edges as we always have *some* transitive ref edge
// chain. While in some cases these edges are direct calls inside the
// callee, they have to be modeled in the inliner as reference edges as
// there may be a reference edge anywhere along the chain from the current
// caller to the callee that causes the whole thing to appear like
// a (transitive) reference edge that will require promotion to a call edge
// below.
for (Function *InlinedCallee : InlinedCallees) {
LazyCallGraph::Node &CalleeN = *CG.lookup(*InlinedCallee);
for (LazyCallGraph::Edge &E : CalleeN)
RC->insertTrivialRefEdge(N, *E.getNode());
}
InlinedCallees.clear();
// At this point, since we have made changes we have at least removed
// a call instruction. However, in the process we do some incremental
// simplification of the surrounding code. This simplification can
// essentially do all of the same things as a function pass and we can
// re-use the exact same logic for updating the call graph to reflect the
// change..
C = &updateCGAndAnalysisManagerForFunctionPass(CG, *C, N, AM, UR);
DEBUG(dbgs() << "Updated inlining SCC: " << *C << "\n");
RC = &C->getOuterRefSCC();
} while (!Nodes.empty());
// Now that we've finished inlining all of the calls across this SCC, delete
// all of the trivially dead functions, updating the call graph and the CGSCC
// pass manager in the process.
//
// Note that this walks a pointer set which has non-deterministic order but
// that is OK as all we do is delete things and add pointers to unordered
// sets.
for (Function *DeadF : DeadFunctions) {
// Get the necessary information out of the call graph and nuke the
// function there.
auto &DeadC = *CG.lookupSCC(*CG.lookup(*DeadF));
auto &DeadRC = DeadC.getOuterRefSCC();
CG.removeDeadFunction(*DeadF);
// Mark the relevant parts of the call graph as invalid so we don't visit
// them.
UR.InvalidatedSCCs.insert(&DeadC);
UR.InvalidatedRefSCCs.insert(&DeadRC);
// And delete the actual function from the module.
M.getFunctionList().erase(DeadF);
}
return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
}
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