// does not make relocation semantics or variable liveness explicit. That's
// done by RewriteStatepointsForGC.
//
-// 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.
+// 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".
//
-// There are restrictions on the IR accepted. We require that:
-// - Pointer values may not be cast to integers and back.
-// - Pointers to GC objects must be tagged with address space #1
-// - Pointers loaded from the heap or global variables must refer to the
-// base of an object. In practice, interior pointers are probably fine as
-// long as your GC can handle them, but exterior pointers loaded to from the
-// heap or globals are explicitly unsupported at this time.
+// 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.
//
-// In addition to these fundemental limitations, we currently do not support:
-// - use of indirectbr (in loops which need backedge safepoints)
-// - aggregate types which contain pointers to GC objects
-// - constant pointers to GC objects (other than null)
-// - use of gc_root
+// 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.
//
-// Patches welcome for the later class of items.
+// 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.
//
-// This code is organized in two key concepts:
-// - "parse point" - at these locations (all calls in the current
-// implementation), the garbage collector must be able to inspect
-// and modify all pointers to garbage collected objects. The objects
-// may be arbitrarily relocated and thus the pointers may be modified.
-// - "poll" - this is a location where the compiled code needs to
-// check (or poll) if the running thread needs to collaborate with
-// the garbage collector by taking some action. In this code, the
-// checking condition and action are abstracted via a frontend
-// provided "safepoint_poll" function.
+// 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/PassManager.h"
+#include "llvm/IR/LegacyPassManager.h"
#include "llvm/ADT/SetOperations.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
using namespace llvm;
-// Ignore oppurtunities to avoid placing safepoints on backedges, useful for
+// Ignore opportunities to avoid placing safepoints on backedges, useful for
// validation
-static cl::opt<bool> AllBackedges("spp-all-backedges", cl::init(false));
+static cl::opt<bool> AllBackedges("spp-all-backedges", cl::Hidden,
+ cl::init(false));
/// If true, do not place backedge safepoints in counted loops.
-static cl::opt<bool> SkipCounted("spp-counted", cl::init(true));
+static cl::opt<bool> SkipCounted("spp-counted", cl::Hidden, cl::init(true));
// 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::init(false));
+static cl::opt<bool> SplitBackedge("spp-split-backedge", cl::Hidden,
+ cl::init(false));
// Print tracing output
-static cl::opt<bool> TraceLSP("spp-trace", cl::init(false));
+static cl::opt<bool> TraceLSP("spp-trace", 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 LoopPass {
+/// 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
std::vector<TerminatorInst *> PollLocations;
/// True unless we're running spp-no-calls in which case we need to disable
- /// the call dependend placement opts.
+ /// the call-dependent placement opts.
bool CallSafepointsEnabled;
+
+ ScalarEvolution *SE = nullptr;
+ DominatorTree *DT = nullptr;
+ LoopInfo *LI = nullptr;
+
PlaceBackedgeSafepointsImpl(bool CallSafepoints = false)
- : LoopPass(ID), CallSafepointsEnabled(CallSafepoints) {
+ : FunctionPass(ID), CallSafepointsEnabled(CallSafepoints) {
initializePlaceBackedgeSafepointsImplPass(*PassRegistry::getPassRegistry());
}
- bool runOnLoop(Loop *, LPPassManager &LPM) override;
+ bool runOnLoop(Loop *);
+ void runOnLoopAndSubLoops(Loop *L) {
+ // Visit all the subloops
+ for (auto I = L->begin(), E = L->end(); I != E; I++)
+ runOnLoopAndSubLoops(*I);
+ runOnLoop(L);
+ }
+
+ bool runOnFunction(Function &F) override {
+ SE = &getAnalysis<ScalarEvolution>();
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+ for (auto I = LI->begin(), E = LI->end(); I != E; I++) {
+ runOnLoopAndSubLoops(*I);
+ }
+ return false;
+ }
void getAnalysisUsage(AnalysisUsage &AU) const override {
- // needed for determining if the loop is finite
+ AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<ScalarEvolution>();
- // to ensure each edge has a single backedge
- // TODO: is this still required?
- AU.addRequiredID(LoopSimplifyID);
-
+ AU.addRequired<LoopInfoWrapperPass>();
// 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::init(false));
-static cl::opt<bool> NoCall("spp-no-call", cl::init(false));
-static cl::opt<bool> NoBackedge("spp-no-backedge", cl::init(false));
+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 ModulePass {
+struct PlaceSafepoints : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
- bool EnableEntrySafepoints;
- bool EnableBackedgeSafepoints;
- bool EnableCallSafepoints;
-
- PlaceSafepoints() : ModulePass(ID) {
+ PlaceSafepoints() : FunctionPass(ID) {
initializePlaceSafepointsPass(*PassRegistry::getPassRegistry());
- EnableEntrySafepoints = !NoEntry;
- EnableBackedgeSafepoints = !NoBackedge;
- EnableCallSafepoints = !NoCall;
- }
- bool runOnModule(Module &M) override {
- bool modified = false;
- for (Function &F : M) {
- modified |= runOnFunction(F);
- }
- return modified;
}
- bool runOnFunction(Function &F);
+ bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
// We modify the graph wholesale (inlining, block insertion, etc). We
// not handle the parsability of state at the runtime call, that's the
// callers job.
static void
-InsertSafepointPoll(DominatorTree &DT, Instruction *after,
+InsertSafepointPoll(Instruction *InsertBefore,
std::vector<CallSite> &ParsePointsNeeded /*rval*/);
static bool isGCLeafFunction(const CallSite &CS);
// 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 substaintially more occurences than just
+ // 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,
BasicBlock *Current = Pred;
while (true) {
for (Instruction &I : *Current) {
- if (CallSite CS = &I)
+ if (auto CS = CallSite(&I))
// Note: Technically, needing a safepoint isn't quite the right
// condition here. We should instead be checking if the target method
// has an
}
}
-bool PlaceBackedgeSafepointsImpl::runOnLoop(Loop *L, LPPassManager &LPM) {
- ScalarEvolution *SE = &getAnalysis<ScalarEvolution>();
-
- // Loop through all predecessors of the loop header and identify all
- // backedges. We need to place a safepoint on every backedge (potentially).
- // Note: Due to LoopSimplify there should only be one. Assert? Or can we
- // relax this?
+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();
-
- // TODO: Use the analysis pass infrastructure for this. There is no reason
- // to recalculate this here.
- DominatorTree DT;
- DT.recalculate(*header->getParent());
-
- bool modified = false;
- for (BasicBlock *pred : predecessors(header)) {
- if (!L->contains(pred)) {
- // This is not a backedge, it's coming from outside the loop
- continue;
- }
+ 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
continue;
}
if (CallSafepointsEnabled &&
- containsUnconditionalCallSafepoint(L, header, pred, DT)) {
+ containsUnconditionalCallSafepoint(L, header, pred, *DT)) {
// 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.
// not help runtime performance that much, but it might help our ability to
// optimize the inner loop.
- // We're unconditionally going to modify this loop.
- modified = true;
-
// 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
PollLocations.push_back(term);
}
- return modified;
+ return false;
+}
+
+/// Returns true if an entry safepoint is not required before this callsite in
+/// the caller function.
+static bool doesNotRequireEntrySafepointBefore(const CallSite &CS) {
+ Instruction *Inst = CS.getInstruction();
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+ 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,
// that can grow the stack. This, combined with backedge polls,
// give us all the progress guarantees we need.
- // Due to the way the frontend generates IR, we may have a couple of initial
- // basic blocks before the first bytecode. These will be single-entry
- // single-exit blocks which conceptually are just part of the first 'real
- // basic block'. Since we don't have deopt state until the first bytecode,
- // walk forward until we've found the first unconditional branch or merge.
-
// hasNextInstruction and nextInstruction are used to iterate
// through a "straight line" execution sequence.
for (cursor = F.getEntryBlock().begin(); hasNextInstruction(cursor);
cursor = nextInstruction(cursor)) {
- // We need to stop going forward as soon as we see a call that can
- // grow the stack (i.e. the call target has a non-zero frame
- // size).
- if (CallSite CS = cursor) {
- (void)CS; // Silence an unused variable warning by gcc 4.8.2
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(cursor)) {
- // llvm.assume(...) are not really calls.
- if (II->getIntrinsicID() == Intrinsic::assume) {
- continue;
- }
- }
+ // 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 CS = CallSite(cursor)) {
+ if (doesNotRequireEntrySafepointBefore(CS))
+ continue;
break;
}
}
assert((hasNextInstruction(cursor) || cursor->isTerminator()) &&
"either we stopped because of a call, or because of terminator");
- if (cursor->isTerminator()) {
- return cursor;
- }
-
- BasicBlock *BB = cursor->getParent();
- SplitBlock(BB, cursor, nullptr);
-
- // Note: SplitBlock modifies the DT. Simply passing a Pass (which is a
- // module pass) is not enough.
- DT.recalculate(F);
-#ifndef NDEBUG
- // SplitBlock updates the DT
- DT.verifyDomTree();
-#endif
-
- return BB->getTerminator();
+ return cursor;
}
/// Identify the list of call sites which need to be have parseable state
static void findCallSafepoints(Function &F,
std::vector<CallSite> &Found /*rval*/) {
assert(Found.empty() && "must be empty!");
- for (Instruction &I : inst_range(F)) {
+ for (Instruction &I : instructions(F)) {
Instruction *inst = &I;
if (isa<CallInst>(inst) || isa<InvokeInst>(inst)) {
CallSite CS(inst);
}
}
-static std::string GCSafepointPollName("gc.safepoint_poll");
+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 char *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; }
+
+// Normalize basic block to make it ready to be target of invoke statepoint.
+// Ensure that 'BB' does not have phi nodes. It may require spliting it.
+static BasicBlock *normalizeForInvokeSafepoint(BasicBlock *BB,
+ BasicBlock *InvokeParent) {
+ BasicBlock *ret = BB;
+
+ if (!BB->getUniquePredecessor()) {
+ ret = SplitBlockPredecessors(BB, InvokeParent, "");
+ }
+
+ // Now that 'ret' has unique predecessor we can safely remove all phi nodes
+ // from it
+ FoldSingleEntryPHINodes(ret);
+ assert(!isa<PHINode>(ret->begin()));
+
+ return ret;
+}
+
bool PlaceSafepoints::runOnFunction(Function &F) {
if (F.isDeclaration() || F.empty()) {
// This is a declaration, nothing to do. Must exit early to avoid crash in
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;
+
bool modified = false;
// In various bits below, we rely on the fact that uses are reachable from
// actually insert parse points yet. That will be done for all polls and
// calls in a single pass.
- // Note: With the migration, we need to recompute this for each 'pass'. Once
- // we merge these, we'll do it once before the analysis
DominatorTree DT;
+ DT.recalculate(F);
+ SmallVector<Instruction *, 16> PollsNeeded;
std::vector<CallSite> ParsePointNeeded;
- if (EnableBackedgeSafepoints && !isGCSafepointPoll(F)) {
+ 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.
- FunctionPassManager FPM(F.getParent());
- bool CanAssumeCallSafepoints = EnableCallSafepoints &&
- !isGCSafepointPoll(F);
+ legacy::FunctionPassManager FPM(F.getParent());
+ bool CanAssumeCallSafepoints = enableCallSafepoints(F);
PlaceBackedgeSafepointsImpl *PBS =
new PlaceBackedgeSafepointsImpl(CanAssumeCallSafepoints);
FPM.add(PBS);
- // Note: While the analysis pass itself won't modify the IR, LoopSimplify
- // (which it depends on) may. i.e. analysis must be recalculated after run
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.
+ std::sort(PollLocations.begin(), PollLocations.end(), 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
- for (size_t i = 0; i < PBS->PollLocations.size(); i++) {
+ // The poll location must be the terminator of a loop latch block.
+ for (TerminatorInst *Term : PollLocations) {
// We are inserting a poll, the function is modified
modified = true;
- // The poll location must be the terminator of a loop latch block.
- TerminatorInst *Term = PBS->PollLocations[i];
-
- std::vector<CallSite> ParsePoints;
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
// 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. (Note: This still relies on LoopSimplify.)
- DenseSet<BasicBlock *> Headers;
+ // each.
+ SetVector<BasicBlock *> Headers;
for (unsigned i = 0; i < Term->getNumSuccessors(); i++) {
BasicBlock *Succ = Term->getSuccessor(i);
if (DT.dominates(Succ, Term->getParent())) {
// 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.
- DenseSet<BasicBlock *> SplitBackedges;
+ SetVector<BasicBlock *> SplitBackedges;
for (BasicBlock *Header : Headers) {
- BasicBlock *NewBB = SplitEdge(Term->getParent(), Header, nullptr);
- SplitBackedges.insert(NewBB);
- }
- DT.recalculate(F);
- for (BasicBlock *NewBB : SplitBackedges) {
- InsertSafepointPoll(DT, NewBB->getTerminator(), ParsePoints);
+ BasicBlock *NewBB = SplitEdge(Term->getParent(), Header, &DT);
+ PollsNeeded.push_back(NewBB->getTerminator());
NumBackedgeSafepoints++;
}
-
} else {
// Split the latch block itself, right before the terminator.
- InsertSafepointPoll(DT, Term, ParsePoints);
+ PollsNeeded.push_back(Term);
NumBackedgeSafepoints++;
}
-
- // Record the parse points for later use
- ParsePointNeeded.insert(ParsePointNeeded.end(), ParsePoints.begin(),
- ParsePoints.end());
}
}
- if (EnableEntrySafepoints && !isGCSafepointPoll(F)) {
- DT.recalculate(F);
- Instruction *term = findLocationForEntrySafepoint(F, DT);
- if (!term) {
+ if (enableEntrySafepoints(F)) {
+ Instruction *Location = findLocationForEntrySafepoint(F, DT);
+ if (!Location) {
// policy choice not to insert?
} else {
- std::vector<CallSite> RuntimeCalls;
- InsertSafepointPoll(DT, term, RuntimeCalls);
+ PollsNeeded.push_back(Location);
modified = true;
NumEntrySafepoints++;
- ParsePointNeeded.insert(ParsePointNeeded.end(), RuntimeCalls.begin(),
- RuntimeCalls.end());
}
}
- if (EnableCallSafepoints && !isGCSafepointPoll(F)) {
- DT.recalculate(F);
+ // Now that we've identified all the needed safepoint poll locations, insert
+ // safepoint polls themselves.
+ for (Instruction *PollLocation : PollsNeeded) {
+ std::vector<CallSite> RuntimeCalls;
+ InsertSafepointPoll(PollLocation, RuntimeCalls);
+ ParsePointNeeded.insert(ParsePointNeeded.end(), RuntimeCalls.begin(),
+ RuntimeCalls.end());
+ }
+ PollsNeeded.clear(); // make sure we don't accidentally use
+ // The dominator tree has been invalidated by the inlining performed in the
+ // above loop. TODO: Teach the inliner how to update the dom tree?
+ DT.recalculate(F);
+
+ if (enableCallSafepoints(F)) {
std::vector<CallSite> Calls;
findCallSafepoints(F, Calls);
NumCallSafepoints += Calls.size();
unique_unsorted(ParsePointNeeded);
// Any parse point (no matter what source) will be handled here
- DT.recalculate(F); // Needed?
// We're about to start modifying the function
if (!ParsePointNeeded.empty())
Results.reserve(ParsePointNeeded.size());
for (size_t i = 0; i < ParsePointNeeded.size(); i++) {
CallSite &CS = ParsePointNeeded[i];
+
+ // For invoke statepoints we need to remove all phi nodes at the normal
+ // destination block.
+ // Reason for this is that we can place gc_result only after last phi node
+ // in basic block. We will get malformed code after RAUW for the
+ // gc_result if one of this phi nodes uses result from the invoke.
+ if (InvokeInst *Invoke = dyn_cast<InvokeInst>(CS.getInstruction())) {
+ normalizeForInvokeSafepoint(Invoke->getNormalDest(),
+ Invoke->getParent());
+ }
+
Value *GCResult = ReplaceWithStatepoint(CS, nullptr);
Results.push_back(GCResult);
}
CallSite &CS = ParsePointNeeded[i];
Value *GCResult = Results[i];
if (GCResult) {
- // In case if we inserted result in a different basic block than the
- // original safepoint (this can happen for invokes). We need to be sure
- // that
- // original result value was not used in any of the phi nodes at the
- // beginning of basic block with gc result. Because we know that all such
- // blocks will have single predecessor we can safely assume that all phi
- // nodes have single entry (because of normalizeBBForInvokeSafepoint).
- // Just remove them all here.
- if (CS.isInvoke()) {
- FoldSingleEntryPHINodes(cast<Instruction>(GCResult)->getParent(),
- nullptr);
- assert(
- !isa<PHINode>(cast<Instruction>(GCResult)->getParent()->begin()));
- }
+ // Can not RAUW for the invoke gc result in case of phi nodes preset.
+ assert(CS.isCall() || !isa<PHINode>(cast<Instruction>(GCResult)->getParent()->begin()));
// Replace all uses with the new call
CS.getInstruction()->replaceAllUsesWith(GCResult);
char PlaceBackedgeSafepointsImpl::ID = 0;
char PlaceSafepoints::ID = 0;
-ModulePass *llvm::createPlaceSafepointsPass() { return new PlaceSafepoints(); }
+FunctionPass *llvm::createPlaceSafepointsPass() {
+ return new PlaceSafepoints();
+}
INITIALIZE_PASS_BEGIN(PlaceBackedgeSafepointsImpl,
"place-backedge-safepoints-impl",
"Place Backedge Safepoints", false, false)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
-INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_END(PlaceBackedgeSafepointsImpl,
"place-backedge-safepoints-impl",
"Place Backedge Safepoints", false, false)
// Most LLVM intrinsics are things which can never take a safepoint.
// As a result, we don't need to have the stack parsable at the
// callsite. This is a highly useful optimization since intrinsic
- // calls are fairly prevelent, particularly in debug builds.
+ // calls are fairly prevalent, particularly in debug builds.
return true;
}
}
static void
-InsertSafepointPoll(DominatorTree &DT, Instruction *term,
+InsertSafepointPoll(Instruction *InsertBefore,
std::vector<CallSite> &ParsePointsNeeded /*rval*/) {
- Module *M = term->getParent()->getParent()->getParent();
- assert(M);
+ 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).
- FunctionType *ftype =
- FunctionType::get(Type::getVoidTy(M->getContext()), false);
- assert(ftype && "null?");
- // Note: This cast can fail if there's a function of the same name with a
- // different type inserted previously
- Function *F =
- dyn_cast<Function>(M->getOrInsertFunction("gc.safepoint_poll", ftype));
- assert(F && !F->empty() && "definition must exist");
- CallInst *poll = CallInst::Create(F, "", term);
+
+ auto *F = M->getFunction(GCSafepointPollName);
+ assert(F->getType()->getElementType() ==
+ 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 *OrigBB = term->getParent();
- BasicBlock::iterator before(poll), after(poll);
+ BasicBlock::iterator before(PollCall), after(PollCall);
bool isBegin(false);
- if (before == term->getParent()->begin()) {
+ if (before == OrigBB->begin()) {
isBegin = true;
} else {
before--;
}
after++;
- assert(after != poll->getParent()->end() && "must have successor");
- assert(DT.dominates(before, after) && "trivially true");
+ assert(after != OrigBB->end() && "must have successor");
// do the actual inlining
InlineFunctionInfo IFI;
- bool inlineStatus = InlineFunction(poll, IFI);
- assert(inlineStatus && "inline must succeed");
- (void)inlineStatus; // suppress warning in release-asserts
+ 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");
"malformed poll function");
scanInlinedCode(&*(start), &*(after), calls, BBs);
-
- // Recompute since we've invalidated cached data. Conceptually we
- // shouldn't need to do this, but implementation wise we appear to. Needed
- // so we can insert safepoints correctly.
- // TODO: update more cheaply
- DT.recalculate(*after->getParent()->getParent());
-
assert(!calls.empty() && "slow path not found for safepoint poll");
// Record the fact we need a parsable state at the runtime call contained in
assert(ParsePointsNeeded.size() <= calls.size());
}
-// Normalize basic block to make it ready to be target of invoke statepoint.
-// It means spliting it to have single predecessor. Return newly created BB
-// ready to be successor of invoke statepoint.
-static BasicBlock *normalizeBBForInvokeSafepoint(BasicBlock *BB,
- BasicBlock *InvokeParent) {
- BasicBlock *ret = BB;
-
- if (!BB->getUniquePredecessor()) {
- ret = SplitBlockPredecessors(BB, InvokeParent, "");
- }
-
- // Another requirement for such basic blocks is to not have any phi nodes.
- // Since we just ensured that new BB will have single predecessor,
- // all phi nodes in it will have one value. Here it would be naturall place
- // to
- // remove them all. But we can not do this because we are risking to remove
- // one of the values stored in liveset of another statepoint. We will do it
- // later after placing all safepoints.
-
- return ret;
-}
-
/// Replaces the given call site (Call or Invoke) with a gc.statepoint
/// intrinsic with an empty deoptimization arguments list. This does
/// NOT do explicit relocation for GC support.
static Value *ReplaceWithStatepoint(const CallSite &CS, /* to replace */
Pass *P) {
- BasicBlock *BB = CS.getInstruction()->getParent();
- Function *F = BB->getParent();
- Module *M = F->getParent();
- assert(M && "must be set");
+ assert(CS.getInstruction()->getParent()->getParent()->getParent() &&
+ "must be set");
// TODO: technically, a pass is not allowed to get functions from within a
// function pass since it might trigger a new function addition. Refactor
// this logic out to the initialization of the pass. Doesn't appear to
// matter in practice.
- // Fill in the one generic type'd argument (the function is also vararg)
- std::vector<Type *> argTypes;
- argTypes.push_back(CS.getCalledValue()->getType());
-
- Function *gc_statepoint_decl = Intrinsic::getDeclaration(
- M, Intrinsic::experimental_gc_statepoint, argTypes);
-
// Then go ahead and use the builder do actually do the inserts. We insert
// immediately before the previous instruction under the assumption that all
// arguments will be available here. We can't insert afterwards since we may
// be replacing a terminator.
- Instruction *insertBefore = CS.getInstruction();
- IRBuilder<> Builder(insertBefore);
- // First, create the statepoint (with all live ptrs as arguments).
- std::vector<llvm::Value *> args;
- // target, #call args, unused, call args..., #deopt args, deopt args..., gc args...
- Value *Target = CS.getCalledValue();
- args.push_back(Target);
- int callArgSize = CS.arg_size();
- args.push_back(
- ConstantInt::get(Type::getInt32Ty(M->getContext()), callArgSize));
- // TODO: add a 'Needs GC-rewrite' later flag
- args.push_back(ConstantInt::get(Type::getInt32Ty(M->getContext()), 0));
-
- // Copy all the arguments of the original call
- args.insert(args.end(), CS.arg_begin(), CS.arg_end());
-
- // # of deopt arguments: this pass currently does not support the
- // identification of deopt arguments. If this is interesting to you,
- // please ask on llvm-dev.
- args.push_back(ConstantInt::get(Type::getInt32Ty(M->getContext()), 0));
+ IRBuilder<> Builder(CS.getInstruction());
// Note: The gc args are not filled in at this time, that's handled by
// RewriteStatepointsForGC (which is currently under review).
// Create the statepoint given all the arguments
- Instruction *token = nullptr;
- AttributeSet return_attributes;
- if (CS.isCall()) {
- CallInst *toReplace = cast<CallInst>(CS.getInstruction());
- CallInst *call =
- Builder.CreateCall(gc_statepoint_decl, args, "safepoint_token");
- call->setTailCall(toReplace->isTailCall());
- call->setCallingConv(toReplace->getCallingConv());
-
- // Before we have to worry about GC semantics, all attributes are legal
- AttributeSet new_attrs = toReplace->getAttributes();
- // In case if we can handle this set of sttributes - set up function attrs
- // directly on statepoint and return attrs later for gc_result intrinsic.
- call->setAttributes(new_attrs.getFnAttributes());
- return_attributes = new_attrs.getRetAttributes();
- // TODO: handle param attributes
-
- token = call;
-
- // Put the following gc_result and gc_relocate calls immediately after the
- // the old call (which we're about to delete)
- BasicBlock::iterator next(toReplace);
- assert(BB->end() != next && "not a terminator, must have next");
- next++;
- Instruction *IP = &*(next);
- Builder.SetInsertPoint(IP);
- Builder.SetCurrentDebugLocation(IP->getDebugLoc());
+ Instruction *Token = nullptr;
+
+ uint64_t ID;
+ uint32_t NumPatchBytes;
+ AttributeSet OriginalAttrs = CS.getAttributes();
+ Attribute AttrID =
+ OriginalAttrs.getAttribute(AttributeSet::FunctionIndex, "statepoint-id");
+ Attribute AttrNumPatchBytes = OriginalAttrs.getAttribute(
+ AttributeSet::FunctionIndex, "statepoint-num-patch-bytes");
+
+ AttrBuilder AttrsToRemove;
+ bool HasID = AttrID.isStringAttribute() &&
+ !AttrID.getValueAsString().getAsInteger(10, ID);
+
+ if (HasID)
+ AttrsToRemove.addAttribute("statepoint-id");
+ else
+ ID = 0xABCDEF00;
+
+ bool HasNumPatchBytes =
+ AttrNumPatchBytes.isStringAttribute() &&
+ !AttrNumPatchBytes.getValueAsString().getAsInteger(10, NumPatchBytes);
+
+ if (HasNumPatchBytes)
+ AttrsToRemove.addAttribute("statepoint-num-patch-bytes");
+ else
+ NumPatchBytes = 0;
+
+ OriginalAttrs = OriginalAttrs.removeAttributes(
+ CS.getInstruction()->getContext(), AttributeSet::FunctionIndex,
+ AttrsToRemove);
+
+ if (CS.isCall()) {
+ CallInst *ToReplace = cast<CallInst>(CS.getInstruction());
+ CallInst *Call = Builder.CreateGCStatepointCall(
+ ID, NumPatchBytes, CS.getCalledValue(),
+ makeArrayRef(CS.arg_begin(), CS.arg_end()), None, None,
+ "safepoint_token");
+ Call->setTailCall(ToReplace->isTailCall());
+ Call->setCallingConv(ToReplace->getCallingConv());
+
+ // In case if we can handle this set of attributes - set up function
+ // attributes directly on statepoint and return attributes later for
+ // gc_result intrinsic.
+ Call->setAttributes(OriginalAttrs.getFnAttributes());
+
+ Token = Call;
+
+ // Put the following gc_result and gc_relocate calls immediately after
+ // the old call (which we're about to delete).
+ assert(ToReplace->getNextNode() && "not a terminator, must have next");
+ Builder.SetInsertPoint(ToReplace->getNextNode());
+ Builder.SetCurrentDebugLocation(ToReplace->getNextNode()->getDebugLoc());
} else if (CS.isInvoke()) {
- InvokeInst *toReplace = cast<InvokeInst>(CS.getInstruction());
+ InvokeInst *ToReplace = cast<InvokeInst>(CS.getInstruction());
// Insert the new invoke into the old block. We'll remove the old one in a
// moment at which point this will become the new terminator for the
// original block.
- InvokeInst *invoke = InvokeInst::Create(
- gc_statepoint_decl, toReplace->getNormalDest(),
- toReplace->getUnwindDest(), args, "", toReplace->getParent());
- invoke->setCallingConv(toReplace->getCallingConv());
+ Builder.SetInsertPoint(ToReplace->getParent());
+ InvokeInst *Invoke = Builder.CreateGCStatepointInvoke(
+ ID, NumPatchBytes, CS.getCalledValue(), ToReplace->getNormalDest(),
+ ToReplace->getUnwindDest(), makeArrayRef(CS.arg_begin(), CS.arg_end()),
+ None, None, "safepoint_token");
- // Currently we will fail on parameter attributes and on certain
- // function attributes.
- AttributeSet new_attrs = toReplace->getAttributes();
- // In case if we can handle this set of sttributes - set up function attrs
- // directly on statepoint and return attrs later for gc_result intrinsic.
- invoke->setAttributes(new_attrs.getFnAttributes());
- return_attributes = new_attrs.getRetAttributes();
+ Invoke->setCallingConv(ToReplace->getCallingConv());
- token = invoke;
+ // In case if we can handle this set of attributes - set up function
+ // attributes directly on statepoint and return attributes later for
+ // gc_result intrinsic.
+ Invoke->setAttributes(OriginalAttrs.getFnAttributes());
+
+ Token = Invoke;
// We'll insert the gc.result into the normal block
- BasicBlock *normalDest = normalizeBBForInvokeSafepoint(
- toReplace->getNormalDest(), invoke->getParent());
- Instruction *IP = &*(normalDest->getFirstInsertionPt());
+ BasicBlock *NormalDest = ToReplace->getNormalDest();
+ // Can not insert gc.result in case of phi nodes preset.
+ // Should have removed this cases prior to running this function
+ assert(!isa<PHINode>(NormalDest->begin()));
+ Instruction *IP = &*(NormalDest->getFirstInsertionPt());
Builder.SetInsertPoint(IP);
} else {
llvm_unreachable("unexpect type of CallSite");
}
- assert(token);
+ assert(Token);
// Handle the return value of the original call - update all uses to use a
// gc_result hanging off the statepoint node we just inserted
// Only add the gc_result iff there is actually a used result
if (!CS.getType()->isVoidTy() && !CS.getInstruction()->use_empty()) {
- Instruction *gc_result = nullptr;
- std::vector<Type *> types; // one per 'any' type
- types.push_back(CS.getType()); // result type
- auto get_gc_result_id = [&](Type &Ty) {
- if (Ty.isIntegerTy()) {
- return Intrinsic::experimental_gc_result_int;
- } else if (Ty.isFloatingPointTy()) {
- return Intrinsic::experimental_gc_result_float;
- } else if (Ty.isPointerTy()) {
- return Intrinsic::experimental_gc_result_ptr;
- } else {
- llvm_unreachable("non java type encountered");
- }
- };
- Intrinsic::ID Id = get_gc_result_id(*CS.getType());
- Value *gc_result_func = Intrinsic::getDeclaration(M, Id, types);
-
- std::vector<Value *> args;
- args.push_back(token);
- gc_result = Builder.CreateCall(
- gc_result_func, args,
- CS.getInstruction()->hasName() ? CS.getInstruction()->getName() : "");
-
- cast<CallInst>(gc_result)->setAttributes(return_attributes);
- return gc_result;
+ std::string TakenName =
+ CS.getInstruction()->hasName() ? CS.getInstruction()->getName() : "";
+ CallInst *GCResult = Builder.CreateGCResult(Token, CS.getType(), TakenName);
+ GCResult->setAttributes(OriginalAttrs.getRetAttributes());
+ return GCResult;
} else {
// No return value for the call.
return nullptr;
projects / oota-llvm.git / blobdiff