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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.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "inline"
+#include "llvm/Module.h"
+#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
+#include "llvm/Analysis/CallGraph.h"
+#include "llvm/Analysis/InlineCost.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Transforms/IPO/InlinerPass.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
+#include <set>
+using namespace llvm;
+
+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");
+
+static cl::opt<int>
+InlineLimit("inline-threshold", cl::Hidden, cl::init(225), cl::ZeroOrMore,
+ cl::desc("Control the amount of inlining to perform (default = 225)"));
+
+static cl::opt<int>
+HintThreshold("inlinehint-threshold", cl::Hidden, cl::init(325),
+ cl::desc("Threshold for inlining functions with inline hint"));
+
+// Threshold to use when optsize is specified (and there is no -inline-limit).
+const int OptSizeThreshold = 75;
+
+Inliner::Inliner(void *ID)
+ : CallGraphSCCPass(ID), InlineThreshold(InlineLimit) {}
+
+Inliner::Inliner(void *ID, int Threshold)
+ : CallGraphSCCPass(ID), InlineThreshold(Threshold) {}
+
+/// getAnalysisUsage - For this class, we declare that we require and preserve
+/// the call graph. If the derived class implements this method, it should
+/// always explicitly call the implementation here.
+void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
+ CallGraphSCCPass::getAnalysisUsage(Info);
+}
+
+
+typedef DenseMap<const ArrayType*, std::vector<AllocaInst*> >
+InlinedArrayAllocasTy;
+
+/// InlineCallIfPossible - 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) {
+ Function *Callee = CS.getCalledFunction();
+ Function *Caller = CS.getCaller();
+
+ // Try to inline the function. Get the list of static allocas that were
+ // inlined.
+ if (!InlineFunction(CS, IFI))
+ return false;
+
+ // If the inlined function had a higher stack protection level than the
+ // calling function, then bump up the caller's stack protection level.
+ if (Callee->hasFnAttr(Attribute::StackProtectReq))
+ Caller->addFnAttr(Attribute::StackProtectReq);
+ else if (Callee->hasFnAttr(Attribute::StackProtect) &&
+ !Caller->hasFnAttr(Attribute::StackProtectReq))
+ Caller->addFnAttr(Attribute::StackProtect);
+
+
+ // 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.
+ //
+ SmallPtrSet<AllocaInst*, 16> UsedAllocas;
+
+ // 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).
+ const ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
+ if (ATy == 0 || 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 (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
+ AllocaInst *AvailableAlloca = AllocasForType[i];
+
+ // 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))
+ continue;
+
+ // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
+ // success!
+ DEBUG(dbgs() << " ***MERGED ALLOCA: " << *AI);
+
+ AI->replaceAllUsesWith(AvailableAlloca);
+ AI->eraseFromParent();
+ MergedAwayAlloca = true;
+ ++NumMergedAllocas;
+ 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);
+ }
+
+ return true;
+}
+
+unsigned Inliner::getInlineThreshold(CallSite CS) const {
+ int thres = InlineThreshold;
+
+ // Listen to optsize when -inline-limit is not given.
+ Function *Caller = CS.getCaller();
+ if (Caller && !Caller->isDeclaration() &&
+ Caller->hasFnAttr(Attribute::OptimizeForSize) &&
+ InlineLimit.getNumOccurrences() == 0)
+ thres = OptSizeThreshold;
+
+ // Listen to inlinehint when it would increase the threshold.
+ Function *Callee = CS.getCalledFunction();
+ if (HintThreshold > thres && Callee && !Callee->isDeclaration() &&
+ Callee->hasFnAttr(Attribute::InlineHint))
+ thres = HintThreshold;
+
+ return thres;
+}
+
+/// shouldInline - Return true if the inliner should attempt to inline
+/// at the given CallSite.
+bool Inliner::shouldInline(CallSite CS) {
+ InlineCost IC = getInlineCost(CS);
+
+ if (IC.isAlways()) {
+ DEBUG(dbgs() << " Inlining: cost=always"
+ << ", Call: " << *CS.getInstruction() << "\n");
+ return true;
+ }
+
+ if (IC.isNever()) {
+ DEBUG(dbgs() << " NOT Inlining: cost=never"
+ << ", Call: " << *CS.getInstruction() << "\n");
+ return false;
+ }
+
+ int Cost = IC.getValue();
+ Function *Caller = CS.getCaller();
+ int CurrentThreshold = getInlineThreshold(CS);
+ float FudgeFactor = getInlineFudgeFactor(CS);
+ int AdjThreshold = (int)(CurrentThreshold * FudgeFactor);
+ if (Cost >= AdjThreshold) {
+ DEBUG(dbgs() << " NOT Inlining: cost=" << Cost
+ << ", thres=" << AdjThreshold
+ << ", Call: " << *CS.getInstruction() << "\n");
+ return false;
+ }
+
+ // Try to detect the case where the current inlining candidate caller
+ // (call it B) is a static 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.
+ if (Caller->hasLocalLinkage()) {
+ int TotalSecondaryCost = 0;
+ bool outerCallsFound = false;
+ bool allOuterCallsWillBeInlined = true;
+ bool someOuterCallWouldNotBeInlined = false;
+ for (Value::use_iterator I = Caller->use_begin(), E =Caller->use_end();
+ I != E; ++I) {
+ CallSite CS2 = CallSite::get(*I);
+
+ // If this isn't a call to Caller (it could be some other sort
+ // of reference) skip it.
+ if (CS2.getInstruction() == 0 || CS2.getCalledFunction() != Caller)
+ continue;
+
+ InlineCost IC2 = getInlineCost(CS2);
+ if (IC2.isNever())
+ allOuterCallsWillBeInlined = false;
+ if (IC2.isAlways() || IC2.isNever())
+ continue;
+
+ outerCallsFound = true;
+ int Cost2 = IC2.getValue();
+ int CurrentThreshold2 = getInlineThreshold(CS2);
+ float FudgeFactor2 = getInlineFudgeFactor(CS2);
+
+ if (Cost2 >= (int)(CurrentThreshold2 * FudgeFactor2))
+ allOuterCallsWillBeInlined = false;
+
+ // See if we have this case. We subtract off the penalty
+ // for the call instruction, which we would be deleting.
+ if (Cost2 < (int)(CurrentThreshold2 * FudgeFactor2) &&
+ Cost2 + Cost - (InlineConstants::CallPenalty + 1) >=
+ (int)(CurrentThreshold2 * FudgeFactor2)) {
+ someOuterCallWouldNotBeInlined = true;
+ TotalSecondaryCost += Cost2;
+ }
+ }
+ // 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 (allOuterCallsWillBeInlined && Caller->use_begin() != Caller->use_end())
+ TotalSecondaryCost += InlineConstants::LastCallToStaticBonus;
+
+ if (outerCallsFound && someOuterCallWouldNotBeInlined &&
+ TotalSecondaryCost < Cost) {
+ DEBUG(dbgs() << " NOT Inlining: " << *CS.getInstruction() <<
+ " Cost = " << Cost <<
+ ", outer Cost = " << TotalSecondaryCost << '\n');
+ return false;
+ }
+ }
+
+ DEBUG(dbgs() << " Inlining: cost=" << Cost
+ << ", thres=" << AdjThreshold
+ << ", Call: " << *CS.getInstruction() << '\n');
+ return true;
+}
+
+/// InlineHistoryIncludes - 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 Inliner::runOnSCC(CallGraphSCC &SCC) {
+ CallGraph &CG = getAnalysis<CallGraph>();
+ const TargetData *TD = getAnalysisIfAvailable<TargetData>();
+
+ SmallPtrSet<Function*, 8> SCCFunctions;
+ DEBUG(dbgs() << "Inliner visiting SCC:");
+ for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
+ Function *F = (*I)->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 (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
+ Function *F = (*I)->getFunction();
+ if (!F) continue;
+
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ CallSite CS = CallSite::get(I);
+ // If this isn't a call, or it is a call to an intrinsic, it can
+ // never be inlined.
+ if (CS.getInstruction() == 0 || 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 (CS.getCalledFunction() && CS.getCalledFunction()->isDeclaration())
+ 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, TD);
+
+ // 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.
+ 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())) {
+ 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;
+ // Update the cached cost info with the missing call
+ growCachedCostInfo(Caller, NULL);
+ } else {
+ // We can only inline direct calls to non-declarations.
+ if (Callee == 0 || Callee->isDeclaration()) continue;
+
+ // If this call sites 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 inlinling 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;
+
+
+ // If the policy determines that we should inline this function,
+ // try to do so.
+ if (!shouldInline(CS))
+ continue;
+
+ // Attempt to inline the function.
+ if (!InlineCallIfPossible(CS, InlineInfo, InlinedArrayAllocas))
+ continue;
+ ++NumInlined;
+
+ // 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 (unsigned i = 0, e = InlineInfo.InlinedCalls.size();
+ i != e; ++i) {
+ Value *Ptr = InlineInfo.InlinedCalls[i];
+ CallSites.push_back(std::make_pair(CallSite(Ptr), NewHistoryID));
+ }
+ }
+
+ // Update the cached cost info with the inlined call.
+ growCachedCostInfo(Caller, Callee);
+ }
+
+ // 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();
+
+ resetCachedCostInfo(Callee);
+
+ // 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()) {
+ std::swap(CallSites[CSi], CallSites.back());
+ CallSites.pop_back();
+ } else {
+ CallSites.erase(CallSites.begin()+CSi);
+ }
+ --CSi;
+
+ Changed = true;
+ LocalChange = true;
+ }
+ } while (LocalChange);
+
+ return Changed;
+}
+
+// doFinalization - Remove now-dead linkonce functions at the end of
+// processing to avoid breaking the SCC traversal.
+bool Inliner::doFinalization(CallGraph &CG) {
+ return removeDeadFunctions(CG);
+}
+
+/// removeDeadFunctions - Remove dead functions that are not included in
+/// DNR (Do Not Remove) list.
+bool Inliner::removeDeadFunctions(CallGraph &CG,
+ SmallPtrSet<const Function *, 16> *DNR) {
+ SmallPtrSet<CallGraphNode*, 16> FunctionsToRemove;
+
+ // 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 (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
+ CallGraphNode *CGN = I->second;
+ if (CGN->getFunction() == 0)
+ continue;
+
+ Function *F = CGN->getFunction();
+
+ // If the only remaining users of the function are dead constants, remove
+ // them.
+ F->removeDeadConstantUsers();
+
+ if (DNR && DNR->count(F))
+ continue;
+ if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage() &&
+ !F->hasAvailableExternallyLinkage())
+ continue;
+ if (!F->use_empty())
+ continue;
+
+ // 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.insert(CGN);
+ }
+
+ // 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 set
+ // here to do this, it doesn't matter which order the functions are deleted
+ // in.
+ bool Changed = false;
+ for (SmallPtrSet<CallGraphNode*, 16>::iterator I = FunctionsToRemove.begin(),
+ E = FunctionsToRemove.end(); I != E; ++I) {
+ resetCachedCostInfo((*I)->getFunction());
+ delete CG.removeFunctionFromModule(*I);
+ ++NumDeleted;
+ Changed = true;
+ }
+
+ return Changed;
+}
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