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Diffstat (limited to 'contrib/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp | 689 |
1 files changed, 0 insertions, 689 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp b/contrib/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp deleted file mode 100644 index b544f0a39ea8..000000000000 --- a/contrib/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp +++ /dev/null @@ -1,689 +0,0 @@ -//===- PlaceSafepoints.cpp - Place GC Safepoints --------------------------===// -// -// 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 -// -//===----------------------------------------------------------------------===// -// -// Place garbage collection safepoints at appropriate locations in the IR. This -// does not make relocation semantics or variable liveness explicit. That's -// done by RewriteStatepointsForGC. -// -// Terminology: -// - A call is said to be "parseable" if there is a stack map generated for the -// return PC of the call. A runtime can determine where values listed in the -// deopt arguments and (after RewriteStatepointsForGC) gc arguments are located -// on the stack when the code is suspended inside such a call. Every parse -// point is represented by a call wrapped in an gc.statepoint intrinsic. -// - A "poll" is an explicit check in the generated code to determine if the -// runtime needs the generated code to cooperate by calling a helper routine -// and thus suspending its execution at a known state. The call to the helper -// routine will be parseable. The (gc & runtime specific) logic of a poll is -// assumed to be provided in a function of the name "gc.safepoint_poll". -// -// We aim to insert polls such that running code can quickly be brought to a -// well defined state for inspection by the collector. In the current -// implementation, this is done via the insertion of poll sites at method entry -// and the backedge of most loops. We try to avoid inserting more polls than -// are necessary to ensure a finite period between poll sites. This is not -// because the poll itself is expensive in the generated code; it's not. Polls -// do tend to impact the optimizer itself in negative ways; we'd like to avoid -// perturbing the optimization of the method as much as we can. -// -// We also need to make most call sites parseable. The callee might execute a -// poll (or otherwise be inspected by the GC). If so, the entire stack -// (including the suspended frame of the current method) must be parseable. -// -// This pass will insert: -// - Call parse points ("call safepoints") for any call which may need to -// reach a safepoint during the execution of the callee function. -// - Backedge safepoint polls and entry safepoint polls to ensure that -// executing code reaches a safepoint poll in a finite amount of time. -// -// We do not currently support return statepoints, but adding them would not -// be hard. They are not required for correctness - entry safepoints are an -// alternative - but some GCs may prefer them. Patches welcome. -// -//===----------------------------------------------------------------------===// - -#include "llvm/Pass.h" - -#include "llvm/ADT/SetVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/Analysis/CFG.h" -#include "llvm/Analysis/ScalarEvolution.h" -#include "llvm/Analysis/TargetLibraryInfo.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/IR/Dominators.h" -#include "llvm/IR/IntrinsicInst.h" -#include "llvm/IR/LegacyPassManager.h" -#include "llvm/IR/Statepoint.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Debug.h" -#include "llvm/Transforms/Scalar.h" -#include "llvm/Transforms/Utils/BasicBlockUtils.h" -#include "llvm/Transforms/Utils/Cloning.h" - -#define DEBUG_TYPE "safepoint-placement" - -STATISTIC(NumEntrySafepoints, "Number of entry safepoints inserted"); -STATISTIC(NumBackedgeSafepoints, "Number of backedge safepoints inserted"); - -STATISTIC(CallInLoop, - "Number of loops without safepoints due to calls in loop"); -STATISTIC(FiniteExecution, - "Number of loops without safepoints finite execution"); - -using namespace llvm; - -// Ignore opportunities to avoid placing safepoints on backedges, useful for -// validation -static cl::opt<bool> AllBackedges("spp-all-backedges", cl::Hidden, - cl::init(false)); - -/// How narrow does the trip count of a loop have to be to have to be considered -/// "counted"? Counted loops do not get safepoints at backedges. -static cl::opt<int> CountedLoopTripWidth("spp-counted-loop-trip-width", - cl::Hidden, cl::init(32)); - -// If true, split the backedge of a loop when placing the safepoint, otherwise -// split the latch block itself. Both are useful to support for -// experimentation, but in practice, it looks like splitting the backedge -// optimizes better. -static cl::opt<bool> SplitBackedge("spp-split-backedge", cl::Hidden, - cl::init(false)); - -namespace { - -/// An analysis pass whose purpose is to identify each of the backedges in -/// the function which require a safepoint poll to be inserted. -struct PlaceBackedgeSafepointsImpl : public FunctionPass { - static char ID; - - /// The output of the pass - gives a list of each backedge (described by - /// pointing at the branch) which need a poll inserted. - std::vector<Instruction *> PollLocations; - - /// True unless we're running spp-no-calls in which case we need to disable - /// the call-dependent placement opts. - bool CallSafepointsEnabled; - - ScalarEvolution *SE = nullptr; - DominatorTree *DT = nullptr; - LoopInfo *LI = nullptr; - TargetLibraryInfo *TLI = nullptr; - - PlaceBackedgeSafepointsImpl(bool CallSafepoints = false) - : FunctionPass(ID), CallSafepointsEnabled(CallSafepoints) { - initializePlaceBackedgeSafepointsImplPass(*PassRegistry::getPassRegistry()); - } - - bool runOnLoop(Loop *); - void runOnLoopAndSubLoops(Loop *L) { - // Visit all the subloops - for (Loop *I : *L) - runOnLoopAndSubLoops(I); - runOnLoop(L); - } - - bool runOnFunction(Function &F) override { - SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE(); - DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); - LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); - TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); - for (Loop *I : *LI) { - runOnLoopAndSubLoops(I); - } - return false; - } - - void getAnalysisUsage(AnalysisUsage &AU) const override { - AU.addRequired<DominatorTreeWrapperPass>(); - AU.addRequired<ScalarEvolutionWrapperPass>(); - AU.addRequired<LoopInfoWrapperPass>(); - AU.addRequired<TargetLibraryInfoWrapperPass>(); - // We no longer modify the IR at all in this pass. Thus all - // analysis are preserved. - AU.setPreservesAll(); - } -}; -} - -static cl::opt<bool> NoEntry("spp-no-entry", cl::Hidden, cl::init(false)); -static cl::opt<bool> NoCall("spp-no-call", cl::Hidden, cl::init(false)); -static cl::opt<bool> NoBackedge("spp-no-backedge", cl::Hidden, cl::init(false)); - -namespace { -struct PlaceSafepoints : public FunctionPass { - static char ID; // Pass identification, replacement for typeid - - PlaceSafepoints() : FunctionPass(ID) { - initializePlaceSafepointsPass(*PassRegistry::getPassRegistry()); - } - bool runOnFunction(Function &F) override; - - void getAnalysisUsage(AnalysisUsage &AU) const override { - // We modify the graph wholesale (inlining, block insertion, etc). We - // preserve nothing at the moment. We could potentially preserve dom tree - // if that was worth doing - AU.addRequired<TargetLibraryInfoWrapperPass>(); - } -}; -} - -// Insert a safepoint poll immediately before the given instruction. Does -// not handle the parsability of state at the runtime call, that's the -// callers job. -static void -InsertSafepointPoll(Instruction *InsertBefore, - std::vector<CallBase *> &ParsePointsNeeded /*rval*/, - const TargetLibraryInfo &TLI); - -static bool needsStatepoint(CallBase *Call, const TargetLibraryInfo &TLI) { - if (callsGCLeafFunction(Call, TLI)) - return false; - if (auto *CI = dyn_cast<CallInst>(Call)) { - if (CI->isInlineAsm()) - return false; - } - - return !(isStatepoint(Call) || isGCRelocate(Call) || isGCResult(Call)); -} - -/// Returns true if this loop is known to contain a call safepoint which -/// must unconditionally execute on any iteration of the loop which returns -/// to the loop header via an edge from Pred. Returns a conservative correct -/// answer; i.e. false is always valid. -static bool containsUnconditionalCallSafepoint(Loop *L, BasicBlock *Header, - BasicBlock *Pred, - DominatorTree &DT, - const TargetLibraryInfo &TLI) { - // In general, we're looking for any cut of the graph which ensures - // there's a call safepoint along every edge between Header and Pred. - // For the moment, we look only for the 'cuts' that consist of a single call - // instruction in a block which is dominated by the Header and dominates the - // loop latch (Pred) block. Somewhat surprisingly, walking the entire chain - // of such dominating blocks gets substantially more occurrences than just - // checking the Pred and Header blocks themselves. This may be due to the - // density of loop exit conditions caused by range and null checks. - // TODO: structure this as an analysis pass, cache the result for subloops, - // avoid dom tree recalculations - assert(DT.dominates(Header, Pred) && "loop latch not dominated by header?"); - - BasicBlock *Current = Pred; - while (true) { - for (Instruction &I : *Current) { - if (auto *Call = dyn_cast<CallBase>(&I)) - // Note: Technically, needing a safepoint isn't quite the right - // condition here. We should instead be checking if the target method - // has an - // unconditional poll. In practice, this is only a theoretical concern - // since we don't have any methods with conditional-only safepoint - // polls. - if (needsStatepoint(Call, TLI)) - return true; - } - - if (Current == Header) - break; - Current = DT.getNode(Current)->getIDom()->getBlock(); - } - - return false; -} - -/// Returns true if this loop is known to terminate in a finite number of -/// iterations. Note that this function may return false for a loop which -/// does actual terminate in a finite constant number of iterations due to -/// conservatism in the analysis. -static bool mustBeFiniteCountedLoop(Loop *L, ScalarEvolution *SE, - BasicBlock *Pred) { - // A conservative bound on the loop as a whole. - const SCEV *MaxTrips = SE->getMaxBackedgeTakenCount(L); - if (MaxTrips != SE->getCouldNotCompute() && - SE->getUnsignedRange(MaxTrips).getUnsignedMax().isIntN( - CountedLoopTripWidth)) - return true; - - // If this is a conditional branch to the header with the alternate path - // being outside the loop, we can ask questions about the execution frequency - // of the exit block. - if (L->isLoopExiting(Pred)) { - // This returns an exact expression only. TODO: We really only need an - // upper bound here, but SE doesn't expose that. - const SCEV *MaxExec = SE->getExitCount(L, Pred); - if (MaxExec != SE->getCouldNotCompute() && - SE->getUnsignedRange(MaxExec).getUnsignedMax().isIntN( - CountedLoopTripWidth)) - return true; - } - - return /* not finite */ false; -} - -static void scanOneBB(Instruction *Start, Instruction *End, - std::vector<CallInst *> &Calls, - DenseSet<BasicBlock *> &Seen, - std::vector<BasicBlock *> &Worklist) { - for (BasicBlock::iterator BBI(Start), BBE0 = Start->getParent()->end(), - BBE1 = BasicBlock::iterator(End); - BBI != BBE0 && BBI != BBE1; BBI++) { - if (CallInst *CI = dyn_cast<CallInst>(&*BBI)) - Calls.push_back(CI); - - // FIXME: This code does not handle invokes - assert(!isa<InvokeInst>(&*BBI) && - "support for invokes in poll code needed"); - - // Only add the successor blocks if we reach the terminator instruction - // without encountering end first - if (BBI->isTerminator()) { - BasicBlock *BB = BBI->getParent(); - for (BasicBlock *Succ : successors(BB)) { - if (Seen.insert(Succ).second) { - Worklist.push_back(Succ); - } - } - } - } -} - -static void scanInlinedCode(Instruction *Start, Instruction *End, - std::vector<CallInst *> &Calls, - DenseSet<BasicBlock *> &Seen) { - Calls.clear(); - std::vector<BasicBlock *> Worklist; - Seen.insert(Start->getParent()); - scanOneBB(Start, End, Calls, Seen, Worklist); - while (!Worklist.empty()) { - BasicBlock *BB = Worklist.back(); - Worklist.pop_back(); - scanOneBB(&*BB->begin(), End, Calls, Seen, Worklist); - } -} - -bool PlaceBackedgeSafepointsImpl::runOnLoop(Loop *L) { - // Loop through all loop latches (branches controlling backedges). We need - // to place a safepoint on every backedge (potentially). - // Note: In common usage, there will be only one edge due to LoopSimplify - // having run sometime earlier in the pipeline, but this code must be correct - // w.r.t. loops with multiple backedges. - BasicBlock *Header = L->getHeader(); - SmallVector<BasicBlock*, 16> LoopLatches; - L->getLoopLatches(LoopLatches); - for (BasicBlock *Pred : LoopLatches) { - assert(L->contains(Pred)); - - // Make a policy decision about whether this loop needs a safepoint or - // not. Note that this is about unburdening the optimizer in loops, not - // avoiding the runtime cost of the actual safepoint. - if (!AllBackedges) { - if (mustBeFiniteCountedLoop(L, SE, Pred)) { - LLVM_DEBUG(dbgs() << "skipping safepoint placement in finite loop\n"); - FiniteExecution++; - continue; - } - if (CallSafepointsEnabled && - containsUnconditionalCallSafepoint(L, Header, Pred, *DT, *TLI)) { - // Note: This is only semantically legal since we won't do any further - // IPO or inlining before the actual call insertion.. If we hadn't, we - // might latter loose this call safepoint. - LLVM_DEBUG( - dbgs() - << "skipping safepoint placement due to unconditional call\n"); - CallInLoop++; - continue; - } - } - - // TODO: We can create an inner loop which runs a finite number of - // iterations with an outer loop which contains a safepoint. This would - // not help runtime performance that much, but it might help our ability to - // optimize the inner loop. - - // Safepoint insertion would involve creating a new basic block (as the - // target of the current backedge) which does the safepoint (of all live - // variables) and branches to the true header - Instruction *Term = Pred->getTerminator(); - - LLVM_DEBUG(dbgs() << "[LSP] terminator instruction: " << *Term); - - PollLocations.push_back(Term); - } - - return false; -} - -/// Returns true if an entry safepoint is not required before this callsite in -/// the caller function. -static bool doesNotRequireEntrySafepointBefore(CallBase *Call) { - if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Call)) { - switch (II->getIntrinsicID()) { - case Intrinsic::experimental_gc_statepoint: - case Intrinsic::experimental_patchpoint_void: - case Intrinsic::experimental_patchpoint_i64: - // The can wrap an actual call which may grow the stack by an unbounded - // amount or run forever. - return false; - default: - // Most LLVM intrinsics are things which do not expand to actual calls, or - // at least if they do, are leaf functions that cause only finite stack - // growth. In particular, the optimizer likes to form things like memsets - // out of stores in the original IR. Another important example is - // llvm.localescape which must occur in the entry block. Inserting a - // safepoint before it is not legal since it could push the localescape - // out of the entry block. - return true; - } - } - return false; -} - -static Instruction *findLocationForEntrySafepoint(Function &F, - DominatorTree &DT) { - - // Conceptually, this poll needs to be on method entry, but in - // practice, we place it as late in the entry block as possible. We - // can place it as late as we want as long as it dominates all calls - // that can grow the stack. This, combined with backedge polls, - // give us all the progress guarantees we need. - - // hasNextInstruction and nextInstruction are used to iterate - // through a "straight line" execution sequence. - - auto HasNextInstruction = [](Instruction *I) { - if (!I->isTerminator()) - return true; - - BasicBlock *nextBB = I->getParent()->getUniqueSuccessor(); - return nextBB && (nextBB->getUniquePredecessor() != nullptr); - }; - - auto NextInstruction = [&](Instruction *I) { - assert(HasNextInstruction(I) && - "first check if there is a next instruction!"); - - if (I->isTerminator()) - return &I->getParent()->getUniqueSuccessor()->front(); - return &*++I->getIterator(); - }; - - Instruction *Cursor = nullptr; - for (Cursor = &F.getEntryBlock().front(); HasNextInstruction(Cursor); - Cursor = NextInstruction(Cursor)) { - - // We need to ensure a safepoint poll occurs before any 'real' call. The - // easiest way to ensure finite execution between safepoints in the face of - // recursive and mutually recursive functions is to enforce that each take - // a safepoint. Additionally, we need to ensure a poll before any call - // which can grow the stack by an unbounded amount. This isn't required - // for GC semantics per se, but is a common requirement for languages - // which detect stack overflow via guard pages and then throw exceptions. - if (auto *Call = dyn_cast<CallBase>(Cursor)) { - if (doesNotRequireEntrySafepointBefore(Call)) - continue; - break; - } - } - - assert((HasNextInstruction(Cursor) || Cursor->isTerminator()) && - "either we stopped because of a call, or because of terminator"); - - return Cursor; -} - -static const char *const GCSafepointPollName = "gc.safepoint_poll"; - -static bool isGCSafepointPoll(Function &F) { - return F.getName().equals(GCSafepointPollName); -} - -/// Returns true if this function should be rewritten to include safepoint -/// polls and parseable call sites. The main point of this function is to be -/// an extension point for custom logic. -static bool shouldRewriteFunction(Function &F) { - // TODO: This should check the GCStrategy - if (F.hasGC()) { - const auto &FunctionGCName = F.getGC(); - const StringRef StatepointExampleName("statepoint-example"); - const StringRef CoreCLRName("coreclr"); - return (StatepointExampleName == FunctionGCName) || - (CoreCLRName == FunctionGCName); - } else - return false; -} - -// TODO: These should become properties of the GCStrategy, possibly with -// command line overrides. -static bool enableEntrySafepoints(Function &F) { return !NoEntry; } -static bool enableBackedgeSafepoints(Function &F) { return !NoBackedge; } -static bool enableCallSafepoints(Function &F) { return !NoCall; } - -bool PlaceSafepoints::runOnFunction(Function &F) { - if (F.isDeclaration() || F.empty()) { - // This is a declaration, nothing to do. Must exit early to avoid crash in - // dom tree calculation - return false; - } - - if (isGCSafepointPoll(F)) { - // Given we're inlining this inside of safepoint poll insertion, this - // doesn't make any sense. Note that we do make any contained calls - // parseable after we inline a poll. - return false; - } - - if (!shouldRewriteFunction(F)) - return false; - - const TargetLibraryInfo &TLI = - getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); - - bool Modified = false; - - // In various bits below, we rely on the fact that uses are reachable from - // defs. When there are basic blocks unreachable from the entry, dominance - // and reachablity queries return non-sensical results. Thus, we preprocess - // the function to ensure these properties hold. - Modified |= removeUnreachableBlocks(F); - - // STEP 1 - Insert the safepoint polling locations. We do not need to - // actually insert parse points yet. That will be done for all polls and - // calls in a single pass. - - DominatorTree DT; - DT.recalculate(F); - - SmallVector<Instruction *, 16> PollsNeeded; - std::vector<CallBase *> ParsePointNeeded; - - if (enableBackedgeSafepoints(F)) { - // Construct a pass manager to run the LoopPass backedge logic. We - // need the pass manager to handle scheduling all the loop passes - // appropriately. Doing this by hand is painful and just not worth messing - // with for the moment. - legacy::FunctionPassManager FPM(F.getParent()); - bool CanAssumeCallSafepoints = enableCallSafepoints(F); - auto *PBS = new PlaceBackedgeSafepointsImpl(CanAssumeCallSafepoints); - FPM.add(PBS); - FPM.run(F); - - // We preserve dominance information when inserting the poll, otherwise - // we'd have to recalculate this on every insert - DT.recalculate(F); - - auto &PollLocations = PBS->PollLocations; - - auto OrderByBBName = [](Instruction *a, Instruction *b) { - return a->getParent()->getName() < b->getParent()->getName(); - }; - // We need the order of list to be stable so that naming ends up stable - // when we split edges. This makes test cases much easier to write. - llvm::sort(PollLocations, OrderByBBName); - - // We can sometimes end up with duplicate poll locations. This happens if - // a single loop is visited more than once. The fact this happens seems - // wrong, but it does happen for the split-backedge.ll test case. - PollLocations.erase(std::unique(PollLocations.begin(), - PollLocations.end()), - PollLocations.end()); - - // Insert a poll at each point the analysis pass identified - // The poll location must be the terminator of a loop latch block. - for (Instruction *Term : PollLocations) { - // We are inserting a poll, the function is modified - Modified = true; - - if (SplitBackedge) { - // Split the backedge of the loop and insert the poll within that new - // basic block. This creates a loop with two latches per original - // latch (which is non-ideal), but this appears to be easier to - // optimize in practice than inserting the poll immediately before the - // latch test. - - // Since this is a latch, at least one of the successors must dominate - // it. Its possible that we have a) duplicate edges to the same header - // and b) edges to distinct loop headers. We need to insert pools on - // each. - SetVector<BasicBlock *> Headers; - for (unsigned i = 0; i < Term->getNumSuccessors(); i++) { - BasicBlock *Succ = Term->getSuccessor(i); - if (DT.dominates(Succ, Term->getParent())) { - Headers.insert(Succ); - } - } - assert(!Headers.empty() && "poll location is not a loop latch?"); - - // The split loop structure here is so that we only need to recalculate - // the dominator tree once. Alternatively, we could just keep it up to - // date and use a more natural merged loop. - SetVector<BasicBlock *> SplitBackedges; - for (BasicBlock *Header : Headers) { - BasicBlock *NewBB = SplitEdge(Term->getParent(), Header, &DT); - PollsNeeded.push_back(NewBB->getTerminator()); - NumBackedgeSafepoints++; - } - } else { - // Split the latch block itself, right before the terminator. - PollsNeeded.push_back(Term); - NumBackedgeSafepoints++; - } - } - } - - if (enableEntrySafepoints(F)) { - if (Instruction *Location = findLocationForEntrySafepoint(F, DT)) { - PollsNeeded.push_back(Location); - Modified = true; - NumEntrySafepoints++; - } - // TODO: else we should assert that there was, in fact, a policy choice to - // not insert a entry safepoint poll. - } - - // Now that we've identified all the needed safepoint poll locations, insert - // safepoint polls themselves. - for (Instruction *PollLocation : PollsNeeded) { - std::vector<CallBase *> RuntimeCalls; - InsertSafepointPoll(PollLocation, RuntimeCalls, TLI); - ParsePointNeeded.insert(ParsePointNeeded.end(), RuntimeCalls.begin(), - RuntimeCalls.end()); - } - - return Modified; -} - -char PlaceBackedgeSafepointsImpl::ID = 0; -char PlaceSafepoints::ID = 0; - -FunctionPass *llvm::createPlaceSafepointsPass() { - return new PlaceSafepoints(); -} - -INITIALIZE_PASS_BEGIN(PlaceBackedgeSafepointsImpl, - "place-backedge-safepoints-impl", - "Place Backedge Safepoints", false, false) -INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass) -INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) -INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) -INITIALIZE_PASS_END(PlaceBackedgeSafepointsImpl, - "place-backedge-safepoints-impl", - "Place Backedge Safepoints", false, false) - -INITIALIZE_PASS_BEGIN(PlaceSafepoints, "place-safepoints", "Place Safepoints", - false, false) -INITIALIZE_PASS_END(PlaceSafepoints, "place-safepoints", "Place Safepoints", - false, false) - -static void -InsertSafepointPoll(Instruction *InsertBefore, - std::vector<CallBase *> &ParsePointsNeeded /*rval*/, - const TargetLibraryInfo &TLI) { - BasicBlock *OrigBB = InsertBefore->getParent(); - Module *M = InsertBefore->getModule(); - assert(M && "must be part of a module"); - - // Inline the safepoint poll implementation - this will get all the branch, - // control flow, etc.. Most importantly, it will introduce the actual slow - // path call - where we need to insert a safepoint (parsepoint). - - auto *F = M->getFunction(GCSafepointPollName); - assert(F && "gc.safepoint_poll function is missing"); - assert(F->getValueType() == - FunctionType::get(Type::getVoidTy(M->getContext()), false) && - "gc.safepoint_poll declared with wrong type"); - assert(!F->empty() && "gc.safepoint_poll must be a non-empty function"); - CallInst *PollCall = CallInst::Create(F, "", InsertBefore); - - // Record some information about the call site we're replacing - BasicBlock::iterator Before(PollCall), After(PollCall); - bool IsBegin = false; - if (Before == OrigBB->begin()) - IsBegin = true; - else - Before--; - - After++; - assert(After != OrigBB->end() && "must have successor"); - - // Do the actual inlining - InlineFunctionInfo IFI; - bool InlineStatus = InlineFunction(PollCall, IFI); - assert(InlineStatus && "inline must succeed"); - (void)InlineStatus; // suppress warning in release-asserts - - // Check post-conditions - assert(IFI.StaticAllocas.empty() && "can't have allocs"); - - std::vector<CallInst *> Calls; // new calls - DenseSet<BasicBlock *> BBs; // new BBs + insertee - - // Include only the newly inserted instructions, Note: begin may not be valid - // if we inserted to the beginning of the basic block - BasicBlock::iterator Start = IsBegin ? OrigBB->begin() : std::next(Before); - - // If your poll function includes an unreachable at the end, that's not - // valid. Bugpoint likes to create this, so check for it. - assert(isPotentiallyReachable(&*Start, &*After) && - "malformed poll function"); - - scanInlinedCode(&*Start, &*After, Calls, BBs); - assert(!Calls.empty() && "slow path not found for safepoint poll"); - - // Record the fact we need a parsable state at the runtime call contained in - // the poll function. This is required so that the runtime knows how to - // parse the last frame when we actually take the safepoint (i.e. execute - // the slow path) - assert(ParsePointsNeeded.empty()); - for (auto *CI : Calls) { - // No safepoint needed or wanted - if (!needsStatepoint(CI, TLI)) - continue; - - // These are likely runtime calls. Should we assert that via calling - // convention or something? - ParsePointsNeeded.push_back(CI); - } - assert(ParsePointsNeeded.size() <= Calls.size()); -} |