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0df4e22602
Found by -Wmissing-prototypes. NFC. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231664 91177308-0d34-0410-b5e6-96231b3b80d8
1942 lines
74 KiB
C++
1942 lines
74 KiB
C++
//===- RewriteStatepointsForGC.cpp - Make GC relocations explicit ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Rewrite an existing set of gc.statepoints such that they make potential
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// relocations performed by the garbage collector explicit in the IR.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Pass.h"
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#include "llvm/Analysis/CFG.h"
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#include "llvm/ADT/SetOperations.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Statepoint.h"
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#include "llvm/IR/Value.h"
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#include "llvm/IR/Verifier.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/Cloning.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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#define DEBUG_TYPE "rewrite-statepoints-for-gc"
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using namespace llvm;
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// Print tracing output
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static cl::opt<bool> TraceLSP("trace-rewrite-statepoints", cl::Hidden,
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cl::init(false));
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// Print the liveset found at the insert location
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static cl::opt<bool> PrintLiveSet("spp-print-liveset", cl::Hidden,
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cl::init(false));
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static cl::opt<bool> PrintLiveSetSize("spp-print-liveset-size",
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cl::Hidden, cl::init(false));
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// Print out the base pointers for debugging
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static cl::opt<bool> PrintBasePointers("spp-print-base-pointers",
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cl::Hidden, cl::init(false));
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namespace {
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struct RewriteStatepointsForGC : public FunctionPass {
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static char ID; // Pass identification, replacement for typeid
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RewriteStatepointsForGC() : FunctionPass(ID) {
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initializeRewriteStatepointsForGCPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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// We add and rewrite a bunch of instructions, but don't really do much
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// else. We could in theory preserve a lot more analyses here.
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AU.addRequired<DominatorTreeWrapperPass>();
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}
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};
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} // namespace
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char RewriteStatepointsForGC::ID = 0;
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FunctionPass *llvm::createRewriteStatepointsForGCPass() {
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return new RewriteStatepointsForGC();
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}
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INITIALIZE_PASS_BEGIN(RewriteStatepointsForGC, "rewrite-statepoints-for-gc",
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"Make relocations explicit at statepoints", false, false)
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
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INITIALIZE_PASS_END(RewriteStatepointsForGC, "rewrite-statepoints-for-gc",
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"Make relocations explicit at statepoints", false, false)
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namespace {
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// The type of the internal cache used inside the findBasePointers family
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// of functions. From the callers perspective, this is an opaque type and
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// should not be inspected.
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//
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// In the actual implementation this caches two relations:
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// - The base relation itself (i.e. this pointer is based on that one)
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// - The base defining value relation (i.e. before base_phi insertion)
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// Generally, after the execution of a full findBasePointer call, only the
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// base relation will remain. Internally, we add a mixture of the two
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// types, then update all the second type to the first type
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typedef DenseMap<Value *, Value *> DefiningValueMapTy;
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typedef DenseSet<llvm::Value *> StatepointLiveSetTy;
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struct PartiallyConstructedSafepointRecord {
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/// The set of values known to be live accross this safepoint
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StatepointLiveSetTy liveset;
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/// Mapping from live pointers to a base-defining-value
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DenseMap<llvm::Value *, llvm::Value *> PointerToBase;
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/// Any new values which were added to the IR during base pointer analysis
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/// for this safepoint
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DenseSet<llvm::Value *> NewInsertedDefs;
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/// The *new* gc.statepoint instruction itself. This produces the token
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/// that normal path gc.relocates and the gc.result are tied to.
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Instruction *StatepointToken;
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/// Instruction to which exceptional gc relocates are attached
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/// Makes it easier to iterate through them during relocationViaAlloca.
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Instruction *UnwindToken;
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};
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}
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// TODO: Once we can get to the GCStrategy, this becomes
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// Optional<bool> isGCManagedPointer(const Value *V) const override {
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static bool isGCPointerType(const Type *T) {
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if (const PointerType *PT = dyn_cast<PointerType>(T))
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// For the sake of this example GC, we arbitrarily pick addrspace(1) as our
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// GC managed heap. We know that a pointer into this heap needs to be
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// updated and that no other pointer does.
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return (1 == PT->getAddressSpace());
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return false;
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}
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/// Return true if the Value is a gc reference type which is potentially used
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/// after the instruction 'loc'. This is only used with the edge reachability
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/// liveness code. Note: It is assumed the V dominates loc.
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static bool isLiveGCReferenceAt(Value &V, Instruction *loc, DominatorTree &DT,
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LoopInfo *LI) {
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if (!isGCPointerType(V.getType()))
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return false;
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if (V.use_empty())
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return false;
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// Given assumption that V dominates loc, this may be live
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return true;
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}
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#ifndef NDEBUG
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static bool isAggWhichContainsGCPtrType(Type *Ty) {
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if (VectorType *VT = dyn_cast<VectorType>(Ty))
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return isGCPointerType(VT->getScalarType());
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if (ArrayType *AT = dyn_cast<ArrayType>(Ty))
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return isGCPointerType(AT->getElementType()) ||
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isAggWhichContainsGCPtrType(AT->getElementType());
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if (StructType *ST = dyn_cast<StructType>(Ty))
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return std::any_of(ST->subtypes().begin(), ST->subtypes().end(),
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[](Type *SubType) {
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return isGCPointerType(SubType) ||
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isAggWhichContainsGCPtrType(SubType);
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});
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return false;
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}
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#endif
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// Conservatively identifies any definitions which might be live at the
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// given instruction. The analysis is performed immediately before the
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// given instruction. Values defined by that instruction are not considered
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// live. Values used by that instruction are considered live.
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//
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// preconditions: valid IR graph, term is either a terminator instruction or
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// a call instruction, pred is the basic block of term, DT, LI are valid
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//
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// side effects: none, does not mutate IR
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//
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// postconditions: populates liveValues as discussed above
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static void findLiveGCValuesAtInst(Instruction *term, BasicBlock *pred,
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DominatorTree &DT, LoopInfo *LI,
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StatepointLiveSetTy &liveValues) {
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liveValues.clear();
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assert(isa<CallInst>(term) || isa<InvokeInst>(term) || term->isTerminator());
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Function *F = pred->getParent();
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auto is_live_gc_reference =
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[&](Value &V) { return isLiveGCReferenceAt(V, term, DT, LI); };
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// Are there any gc pointer arguments live over this point? This needs to be
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// special cased since arguments aren't defined in basic blocks.
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for (Argument &arg : F->args()) {
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assert(!isAggWhichContainsGCPtrType(arg.getType()) &&
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"support for FCA unimplemented");
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if (is_live_gc_reference(arg)) {
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liveValues.insert(&arg);
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}
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}
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// Walk through all dominating blocks - the ones which can contain
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// definitions used in this block - and check to see if any of the values
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// they define are used in locations potentially reachable from the
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// interesting instruction.
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BasicBlock *BBI = pred;
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while (true) {
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if (TraceLSP) {
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errs() << "[LSP] Looking at dominating block " << pred->getName() << "\n";
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}
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assert(DT.dominates(BBI, pred));
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assert(isPotentiallyReachable(BBI, pred, &DT) &&
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"dominated block must be reachable");
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// Walk through the instructions in dominating blocks and keep any
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// that have a use potentially reachable from the block we're
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// considering putting the safepoint in
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for (Instruction &inst : *BBI) {
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if (TraceLSP) {
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errs() << "[LSP] Looking at instruction ";
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inst.dump();
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}
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if (pred == BBI && (&inst) == term) {
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if (TraceLSP) {
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errs() << "[LSP] stopped because we encountered the safepoint "
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"instruction.\n";
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}
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// If we're in the block which defines the interesting instruction,
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// we don't want to include any values as live which are defined
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// _after_ the interesting line or as part of the line itself
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// i.e. "term" is the call instruction for a call safepoint, the
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// results of the call should not be considered live in that stackmap
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break;
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}
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assert(!isAggWhichContainsGCPtrType(inst.getType()) &&
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"support for FCA unimplemented");
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if (is_live_gc_reference(inst)) {
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if (TraceLSP) {
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errs() << "[LSP] found live value for this safepoint ";
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inst.dump();
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term->dump();
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}
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liveValues.insert(&inst);
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}
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}
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if (!DT.getNode(BBI)->getIDom()) {
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assert(BBI == &F->getEntryBlock() &&
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"failed to find a dominator for something other than "
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"the entry block");
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break;
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}
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BBI = DT.getNode(BBI)->getIDom()->getBlock();
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}
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}
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static bool order_by_name(llvm::Value *a, llvm::Value *b) {
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if (a->hasName() && b->hasName()) {
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return -1 == a->getName().compare(b->getName());
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} else if (a->hasName() && !b->hasName()) {
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return true;
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} else if (!a->hasName() && b->hasName()) {
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return false;
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} else {
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// Better than nothing, but not stable
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return a < b;
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}
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}
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/// Find the initial live set. Note that due to base pointer
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/// insertion, the live set may be incomplete.
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static void
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analyzeParsePointLiveness(DominatorTree &DT, const CallSite &CS,
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PartiallyConstructedSafepointRecord &result) {
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Instruction *inst = CS.getInstruction();
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BasicBlock *BB = inst->getParent();
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StatepointLiveSetTy liveset;
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findLiveGCValuesAtInst(inst, BB, DT, nullptr, liveset);
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if (PrintLiveSet) {
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// Note: This output is used by several of the test cases
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// The order of elemtns in a set is not stable, put them in a vec and sort
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// by name
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SmallVector<Value *, 64> temp;
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temp.insert(temp.end(), liveset.begin(), liveset.end());
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std::sort(temp.begin(), temp.end(), order_by_name);
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errs() << "Live Variables:\n";
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for (Value *V : temp) {
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errs() << " " << V->getName(); // no newline
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V->dump();
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}
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}
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if (PrintLiveSetSize) {
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errs() << "Safepoint For: " << CS.getCalledValue()->getName() << "\n";
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errs() << "Number live values: " << liveset.size() << "\n";
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}
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result.liveset = liveset;
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}
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/// True iff this value is the null pointer constant (of any pointer type)
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static bool LLVM_ATTRIBUTE_UNUSED isNullConstant(Value *V) {
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return isa<Constant>(V) && isa<PointerType>(V->getType()) &&
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cast<Constant>(V)->isNullValue();
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}
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/// Helper function for findBasePointer - Will return a value which either a)
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/// defines the base pointer for the input or b) blocks the simple search
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/// (i.e. a PHI or Select of two derived pointers)
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static Value *findBaseDefiningValue(Value *I) {
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assert(I->getType()->isPointerTy() &&
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"Illegal to ask for the base pointer of a non-pointer type");
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// There are instructions which can never return gc pointer values. Sanity
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// check
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// that this is actually true.
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assert(!isa<InsertElementInst>(I) && !isa<ExtractElementInst>(I) &&
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!isa<ShuffleVectorInst>(I) && "Vector types are not gc pointers");
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assert((!isa<Instruction>(I) || isa<InvokeInst>(I) ||
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!cast<Instruction>(I)->isTerminator()) &&
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"With the exception of invoke terminators don't define values");
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assert(!isa<StoreInst>(I) && !isa<FenceInst>(I) &&
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"Can't be definitions to start with");
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assert(!isa<ICmpInst>(I) && !isa<FCmpInst>(I) &&
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"Comparisons don't give ops");
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// There's a bunch of instructions which just don't make sense to apply to
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// a pointer. The only valid reason for this would be pointer bit
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// twiddling which we're just not going to support.
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assert((!isa<Instruction>(I) || !cast<Instruction>(I)->isBinaryOp()) &&
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"Binary ops on pointer values are meaningless. Unless your "
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"bit-twiddling which we don't support");
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if (Argument *Arg = dyn_cast<Argument>(I)) {
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// An incoming argument to the function is a base pointer
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// We should have never reached here if this argument isn't an gc value
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assert(Arg->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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return Arg;
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}
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if (GlobalVariable *global = dyn_cast<GlobalVariable>(I)) {
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// base case
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assert(global->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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return global;
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}
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// inlining could possibly introduce phi node that contains
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// undef if callee has multiple returns
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if (UndefValue *undef = dyn_cast<UndefValue>(I)) {
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assert(undef->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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return undef; // utterly meaningless, but useful for dealing with
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// partially optimized code.
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}
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// Due to inheritance, this must be _after_ the global variable and undef
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// checks
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if (Constant *con = dyn_cast<Constant>(I)) {
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assert(!isa<GlobalVariable>(I) && !isa<UndefValue>(I) &&
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"order of checks wrong!");
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// Note: Finding a constant base for something marked for relocation
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// doesn't really make sense. The most likely case is either a) some
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// screwed up the address space usage or b) your validating against
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// compiled C++ code w/o the proper separation. The only real exception
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// is a null pointer. You could have generic code written to index of
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// off a potentially null value and have proven it null. We also use
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// null pointers in dead paths of relocation phis (which we might later
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// want to find a base pointer for).
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assert(con->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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assert(con->isNullValue() && "null is the only case which makes sense");
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return con;
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}
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if (CastInst *CI = dyn_cast<CastInst>(I)) {
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Value *def = CI->stripPointerCasts();
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assert(def->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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// If we find a cast instruction here, it means we've found a cast which is
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// not simply a pointer cast (i.e. an inttoptr). We don't know how to
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// handle int->ptr conversion.
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assert(!isa<CastInst>(def) && "shouldn't find another cast here");
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return findBaseDefiningValue(def);
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}
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if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
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if (LI->getType()->isPointerTy()) {
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Value *Op = LI->getOperand(0);
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(void)Op;
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// Has to be a pointer to an gc object, or possibly an array of such?
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assert(Op->getType()->isPointerTy());
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return LI; // The value loaded is an gc base itself
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}
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}
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if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
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Value *Op = GEP->getOperand(0);
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if (Op->getType()->isPointerTy()) {
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return findBaseDefiningValue(Op); // The base of this GEP is the base
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}
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}
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if (AllocaInst *alloc = dyn_cast<AllocaInst>(I)) {
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// An alloca represents a conceptual stack slot. It's the slot itself
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// that the GC needs to know about, not the value in the slot.
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assert(alloc->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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return alloc;
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}
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if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
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switch (II->getIntrinsicID()) {
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default:
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// fall through to general call handling
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break;
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case Intrinsic::experimental_gc_statepoint:
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case Intrinsic::experimental_gc_result_float:
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case Intrinsic::experimental_gc_result_int:
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llvm_unreachable("these don't produce pointers");
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case Intrinsic::experimental_gc_result_ptr:
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// This is just a special case of the CallInst check below to handle a
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// statepoint with deopt args which hasn't been rewritten for GC yet.
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// TODO: Assert that the statepoint isn't rewritten yet.
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return II;
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case Intrinsic::experimental_gc_relocate: {
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// Rerunning safepoint insertion after safepoints are already
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// inserted is not supported. It could probably be made to work,
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// but why are you doing this? There's no good reason.
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llvm_unreachable("repeat safepoint insertion is not supported");
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}
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case Intrinsic::gcroot:
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// Currently, this mechanism hasn't been extended to work with gcroot.
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// There's no reason it couldn't be, but I haven't thought about the
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// implications much.
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llvm_unreachable(
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"interaction with the gcroot mechanism is not supported");
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}
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}
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// We assume that functions in the source language only return base
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// pointers. This should probably be generalized via attributes to support
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// both source language and internal functions.
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if (CallInst *call = dyn_cast<CallInst>(I)) {
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assert(call->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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return call;
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}
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if (InvokeInst *invoke = dyn_cast<InvokeInst>(I)) {
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assert(invoke->getType()->isPointerTy() &&
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"Base for pointer must be another pointer");
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return invoke;
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}
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// I have absolutely no idea how to implement this part yet. It's not
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// neccessarily hard, I just haven't really looked at it yet.
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assert(!isa<LandingPadInst>(I) && "Landing Pad is unimplemented");
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if (AtomicCmpXchgInst *cas = dyn_cast<AtomicCmpXchgInst>(I)) {
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// A CAS is effectively a atomic store and load combined under a
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// predicate. From the perspective of base pointers, we just treat it
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// like a load. We loaded a pointer from a address in memory, that value
|
|
// had better be a valid base pointer.
|
|
return cas->getPointerOperand();
|
|
}
|
|
if (AtomicRMWInst *atomic = dyn_cast<AtomicRMWInst>(I)) {
|
|
assert(AtomicRMWInst::Xchg == atomic->getOperation() &&
|
|
"All others are binary ops which don't apply to base pointers");
|
|
// semantically, a load, store pair. Treat it the same as a standard load
|
|
return atomic->getPointerOperand();
|
|
}
|
|
|
|
// The aggregate ops. Aggregates can either be in the heap or on the
|
|
// stack, but in either case, this is simply a field load. As a result,
|
|
// this is a defining definition of the base just like a load is.
|
|
if (ExtractValueInst *ev = dyn_cast<ExtractValueInst>(I)) {
|
|
return ev;
|
|
}
|
|
|
|
// We should never see an insert vector since that would require we be
|
|
// tracing back a struct value not a pointer value.
|
|
assert(!isa<InsertValueInst>(I) &&
|
|
"Base pointer for a struct is meaningless");
|
|
|
|
// The last two cases here don't return a base pointer. Instead, they
|
|
// return a value which dynamically selects from amoung several base
|
|
// derived pointers (each with it's own base potentially). It's the job of
|
|
// the caller to resolve these.
|
|
if (SelectInst *select = dyn_cast<SelectInst>(I)) {
|
|
return select;
|
|
}
|
|
|
|
return cast<PHINode>(I);
|
|
}
|
|
|
|
/// Returns the base defining value for this value.
|
|
static Value *findBaseDefiningValueCached(Value *I, DefiningValueMapTy &cache) {
|
|
Value *&Cached = cache[I];
|
|
if (!Cached) {
|
|
Cached = findBaseDefiningValue(I);
|
|
}
|
|
assert(cache[I] != nullptr);
|
|
|
|
if (TraceLSP) {
|
|
errs() << "fBDV-cached: " << I->getName() << " -> " << Cached->getName()
|
|
<< "\n";
|
|
}
|
|
return Cached;
|
|
}
|
|
|
|
/// Return a base pointer for this value if known. Otherwise, return it's
|
|
/// base defining value.
|
|
static Value *findBaseOrBDV(Value *I, DefiningValueMapTy &cache) {
|
|
Value *def = findBaseDefiningValueCached(I, cache);
|
|
auto Found = cache.find(def);
|
|
if (Found != cache.end()) {
|
|
// Either a base-of relation, or a self reference. Caller must check.
|
|
return Found->second;
|
|
}
|
|
// Only a BDV available
|
|
return def;
|
|
}
|
|
|
|
/// Given the result of a call to findBaseDefiningValue, or findBaseOrBDV,
|
|
/// is it known to be a base pointer? Or do we need to continue searching.
|
|
static bool isKnownBaseResult(Value *v) {
|
|
if (!isa<PHINode>(v) && !isa<SelectInst>(v)) {
|
|
// no recursion possible
|
|
return true;
|
|
}
|
|
if (cast<Instruction>(v)->getMetadata("is_base_value")) {
|
|
// This is a previously inserted base phi or select. We know
|
|
// that this is a base value.
|
|
return true;
|
|
}
|
|
|
|
// We need to keep searching
|
|
return false;
|
|
}
|
|
|
|
// TODO: find a better name for this
|
|
namespace {
|
|
class PhiState {
|
|
public:
|
|
enum Status { Unknown, Base, Conflict };
|
|
|
|
PhiState(Status s, Value *b = nullptr) : status(s), base(b) {
|
|
assert(status != Base || b);
|
|
}
|
|
PhiState(Value *b) : status(Base), base(b) {}
|
|
PhiState() : status(Unknown), base(nullptr) {}
|
|
|
|
Status getStatus() const { return status; }
|
|
Value *getBase() const { return base; }
|
|
|
|
bool isBase() const { return getStatus() == Base; }
|
|
bool isUnknown() const { return getStatus() == Unknown; }
|
|
bool isConflict() const { return getStatus() == Conflict; }
|
|
|
|
bool operator==(const PhiState &other) const {
|
|
return base == other.base && status == other.status;
|
|
}
|
|
|
|
bool operator!=(const PhiState &other) const { return !(*this == other); }
|
|
|
|
void dump() {
|
|
errs() << status << " (" << base << " - "
|
|
<< (base ? base->getName() : "nullptr") << "): ";
|
|
}
|
|
|
|
private:
|
|
Status status;
|
|
Value *base; // non null only if status == base
|
|
};
|
|
|
|
typedef DenseMap<Value *, PhiState> ConflictStateMapTy;
|
|
// Values of type PhiState form a lattice, and this is a helper
|
|
// class that implementes the meet operation. The meat of the meet
|
|
// operation is implemented in MeetPhiStates::pureMeet
|
|
class MeetPhiStates {
|
|
public:
|
|
// phiStates is a mapping from PHINodes and SelectInst's to PhiStates.
|
|
explicit MeetPhiStates(const ConflictStateMapTy &phiStates)
|
|
: phiStates(phiStates) {}
|
|
|
|
// Destructively meet the current result with the base V. V can
|
|
// either be a merge instruction (SelectInst / PHINode), in which
|
|
// case its status is looked up in the phiStates map; or a regular
|
|
// SSA value, in which case it is assumed to be a base.
|
|
void meetWith(Value *V) {
|
|
PhiState otherState = getStateForBDV(V);
|
|
assert((MeetPhiStates::pureMeet(otherState, currentResult) ==
|
|
MeetPhiStates::pureMeet(currentResult, otherState)) &&
|
|
"math is wrong: meet does not commute!");
|
|
currentResult = MeetPhiStates::pureMeet(otherState, currentResult);
|
|
}
|
|
|
|
PhiState getResult() const { return currentResult; }
|
|
|
|
private:
|
|
const ConflictStateMapTy &phiStates;
|
|
PhiState currentResult;
|
|
|
|
/// Return a phi state for a base defining value. We'll generate a new
|
|
/// base state for known bases and expect to find a cached state otherwise
|
|
PhiState getStateForBDV(Value *baseValue) {
|
|
if (isKnownBaseResult(baseValue)) {
|
|
return PhiState(baseValue);
|
|
} else {
|
|
return lookupFromMap(baseValue);
|
|
}
|
|
}
|
|
|
|
PhiState lookupFromMap(Value *V) {
|
|
auto I = phiStates.find(V);
|
|
assert(I != phiStates.end() && "lookup failed!");
|
|
return I->second;
|
|
}
|
|
|
|
static PhiState pureMeet(const PhiState &stateA, const PhiState &stateB) {
|
|
switch (stateA.getStatus()) {
|
|
case PhiState::Unknown:
|
|
return stateB;
|
|
|
|
case PhiState::Base:
|
|
assert(stateA.getBase() && "can't be null");
|
|
if (stateB.isUnknown())
|
|
return stateA;
|
|
|
|
if (stateB.isBase()) {
|
|
if (stateA.getBase() == stateB.getBase()) {
|
|
assert(stateA == stateB && "equality broken!");
|
|
return stateA;
|
|
}
|
|
return PhiState(PhiState::Conflict);
|
|
}
|
|
assert(stateB.isConflict() && "only three states!");
|
|
return PhiState(PhiState::Conflict);
|
|
|
|
case PhiState::Conflict:
|
|
return stateA;
|
|
}
|
|
llvm_unreachable("only three states!");
|
|
}
|
|
};
|
|
}
|
|
/// For a given value or instruction, figure out what base ptr it's derived
|
|
/// from. For gc objects, this is simply itself. On success, returns a value
|
|
/// which is the base pointer. (This is reliable and can be used for
|
|
/// relocation.) On failure, returns nullptr.
|
|
static Value *findBasePointer(Value *I, DefiningValueMapTy &cache,
|
|
DenseSet<llvm::Value *> &NewInsertedDefs) {
|
|
Value *def = findBaseOrBDV(I, cache);
|
|
|
|
if (isKnownBaseResult(def)) {
|
|
return def;
|
|
}
|
|
|
|
// Here's the rough algorithm:
|
|
// - For every SSA value, construct a mapping to either an actual base
|
|
// pointer or a PHI which obscures the base pointer.
|
|
// - Construct a mapping from PHI to unknown TOP state. Use an
|
|
// optimistic algorithm to propagate base pointer information. Lattice
|
|
// looks like:
|
|
// UNKNOWN
|
|
// b1 b2 b3 b4
|
|
// CONFLICT
|
|
// When algorithm terminates, all PHIs will either have a single concrete
|
|
// base or be in a conflict state.
|
|
// - For every conflict, insert a dummy PHI node without arguments. Add
|
|
// these to the base[Instruction] = BasePtr mapping. For every
|
|
// non-conflict, add the actual base.
|
|
// - For every conflict, add arguments for the base[a] of each input
|
|
// arguments.
|
|
//
|
|
// Note: A simpler form of this would be to add the conflict form of all
|
|
// PHIs without running the optimistic algorithm. This would be
|
|
// analougous to pessimistic data flow and would likely lead to an
|
|
// overall worse solution.
|
|
|
|
ConflictStateMapTy states;
|
|
states[def] = PhiState();
|
|
// Recursively fill in all phis & selects reachable from the initial one
|
|
// for which we don't already know a definite base value for
|
|
// TODO: This should be rewritten with a worklist
|
|
bool done = false;
|
|
while (!done) {
|
|
done = true;
|
|
// Since we're adding elements to 'states' as we run, we can't keep
|
|
// iterators into the set.
|
|
SmallVector<Value*, 16> Keys;
|
|
Keys.reserve(states.size());
|
|
for (auto Pair : states) {
|
|
Value *V = Pair.first;
|
|
Keys.push_back(V);
|
|
}
|
|
for (Value *v : Keys) {
|
|
assert(!isKnownBaseResult(v) && "why did it get added?");
|
|
if (PHINode *phi = dyn_cast<PHINode>(v)) {
|
|
assert(phi->getNumIncomingValues() > 0 &&
|
|
"zero input phis are illegal");
|
|
for (Value *InVal : phi->incoming_values()) {
|
|
Value *local = findBaseOrBDV(InVal, cache);
|
|
if (!isKnownBaseResult(local) && states.find(local) == states.end()) {
|
|
states[local] = PhiState();
|
|
done = false;
|
|
}
|
|
}
|
|
} else if (SelectInst *sel = dyn_cast<SelectInst>(v)) {
|
|
Value *local = findBaseOrBDV(sel->getTrueValue(), cache);
|
|
if (!isKnownBaseResult(local) && states.find(local) == states.end()) {
|
|
states[local] = PhiState();
|
|
done = false;
|
|
}
|
|
local = findBaseOrBDV(sel->getFalseValue(), cache);
|
|
if (!isKnownBaseResult(local) && states.find(local) == states.end()) {
|
|
states[local] = PhiState();
|
|
done = false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (TraceLSP) {
|
|
errs() << "States after initialization:\n";
|
|
for (auto Pair : states) {
|
|
Instruction *v = cast<Instruction>(Pair.first);
|
|
PhiState state = Pair.second;
|
|
state.dump();
|
|
v->dump();
|
|
}
|
|
}
|
|
|
|
// TODO: come back and revisit the state transitions around inputs which
|
|
// have reached conflict state. The current version seems too conservative.
|
|
|
|
bool progress = true;
|
|
while (progress) {
|
|
#ifndef NDEBUG
|
|
size_t oldSize = states.size();
|
|
#endif
|
|
progress = false;
|
|
// We're only changing keys in this loop, thus safe to keep iterators
|
|
for (auto Pair : states) {
|
|
MeetPhiStates calculateMeet(states);
|
|
Value *v = Pair.first;
|
|
assert(!isKnownBaseResult(v) && "why did it get added?");
|
|
if (SelectInst *select = dyn_cast<SelectInst>(v)) {
|
|
calculateMeet.meetWith(findBaseOrBDV(select->getTrueValue(), cache));
|
|
calculateMeet.meetWith(findBaseOrBDV(select->getFalseValue(), cache));
|
|
} else
|
|
for (Value *Val : cast<PHINode>(v)->incoming_values())
|
|
calculateMeet.meetWith(findBaseOrBDV(Val, cache));
|
|
|
|
PhiState oldState = states[v];
|
|
PhiState newState = calculateMeet.getResult();
|
|
if (oldState != newState) {
|
|
progress = true;
|
|
states[v] = newState;
|
|
}
|
|
}
|
|
|
|
assert(oldSize <= states.size());
|
|
assert(oldSize == states.size() || progress);
|
|
}
|
|
|
|
if (TraceLSP) {
|
|
errs() << "States after meet iteration:\n";
|
|
for (auto Pair : states) {
|
|
Instruction *v = cast<Instruction>(Pair.first);
|
|
PhiState state = Pair.second;
|
|
state.dump();
|
|
v->dump();
|
|
}
|
|
}
|
|
|
|
// Insert Phis for all conflicts
|
|
// We want to keep naming deterministic in the loop that follows, so
|
|
// sort the keys before iteration. This is useful in allowing us to
|
|
// write stable tests. Note that there is no invalidation issue here.
|
|
SmallVector<Value*, 16> Keys;
|
|
Keys.reserve(states.size());
|
|
for (auto Pair : states) {
|
|
Value *V = Pair.first;
|
|
Keys.push_back(V);
|
|
}
|
|
std::sort(Keys.begin(), Keys.end(), order_by_name);
|
|
// TODO: adjust naming patterns to avoid this order of iteration dependency
|
|
for (Value *V : Keys) {
|
|
Instruction *v = cast<Instruction>(V);
|
|
PhiState state = states[V];
|
|
assert(!isKnownBaseResult(v) && "why did it get added?");
|
|
assert(!state.isUnknown() && "Optimistic algorithm didn't complete!");
|
|
if (!state.isConflict())
|
|
continue;
|
|
|
|
if (isa<PHINode>(v)) {
|
|
int num_preds =
|
|
std::distance(pred_begin(v->getParent()), pred_end(v->getParent()));
|
|
assert(num_preds > 0 && "how did we reach here");
|
|
PHINode *phi = PHINode::Create(v->getType(), num_preds, "base_phi", v);
|
|
NewInsertedDefs.insert(phi);
|
|
// Add metadata marking this as a base value
|
|
auto *const_1 = ConstantInt::get(
|
|
Type::getInt32Ty(
|
|
v->getParent()->getParent()->getParent()->getContext()),
|
|
1);
|
|
auto MDConst = ConstantAsMetadata::get(const_1);
|
|
MDNode *md = MDNode::get(
|
|
v->getParent()->getParent()->getParent()->getContext(), MDConst);
|
|
phi->setMetadata("is_base_value", md);
|
|
states[v] = PhiState(PhiState::Conflict, phi);
|
|
} else {
|
|
SelectInst *sel = cast<SelectInst>(v);
|
|
// The undef will be replaced later
|
|
UndefValue *undef = UndefValue::get(sel->getType());
|
|
SelectInst *basesel = SelectInst::Create(sel->getCondition(), undef,
|
|
undef, "base_select", sel);
|
|
NewInsertedDefs.insert(basesel);
|
|
// Add metadata marking this as a base value
|
|
auto *const_1 = ConstantInt::get(
|
|
Type::getInt32Ty(
|
|
v->getParent()->getParent()->getParent()->getContext()),
|
|
1);
|
|
auto MDConst = ConstantAsMetadata::get(const_1);
|
|
MDNode *md = MDNode::get(
|
|
v->getParent()->getParent()->getParent()->getContext(), MDConst);
|
|
basesel->setMetadata("is_base_value", md);
|
|
states[v] = PhiState(PhiState::Conflict, basesel);
|
|
}
|
|
}
|
|
|
|
// Fixup all the inputs of the new PHIs
|
|
for (auto Pair : states) {
|
|
Instruction *v = cast<Instruction>(Pair.first);
|
|
PhiState state = Pair.second;
|
|
|
|
assert(!isKnownBaseResult(v) && "why did it get added?");
|
|
assert(!state.isUnknown() && "Optimistic algorithm didn't complete!");
|
|
if (!state.isConflict())
|
|
continue;
|
|
|
|
if (PHINode *basephi = dyn_cast<PHINode>(state.getBase())) {
|
|
PHINode *phi = cast<PHINode>(v);
|
|
unsigned NumPHIValues = phi->getNumIncomingValues();
|
|
for (unsigned i = 0; i < NumPHIValues; i++) {
|
|
Value *InVal = phi->getIncomingValue(i);
|
|
BasicBlock *InBB = phi->getIncomingBlock(i);
|
|
|
|
// If we've already seen InBB, add the same incoming value
|
|
// we added for it earlier. The IR verifier requires phi
|
|
// nodes with multiple entries from the same basic block
|
|
// to have the same incoming value for each of those
|
|
// entries. If we don't do this check here and basephi
|
|
// has a different type than base, we'll end up adding two
|
|
// bitcasts (and hence two distinct values) as incoming
|
|
// values for the same basic block.
|
|
|
|
int blockIndex = basephi->getBasicBlockIndex(InBB);
|
|
if (blockIndex != -1) {
|
|
Value *oldBase = basephi->getIncomingValue(blockIndex);
|
|
basephi->addIncoming(oldBase, InBB);
|
|
#ifndef NDEBUG
|
|
Value *base = findBaseOrBDV(InVal, cache);
|
|
if (!isKnownBaseResult(base)) {
|
|
// Either conflict or base.
|
|
assert(states.count(base));
|
|
base = states[base].getBase();
|
|
assert(base != nullptr && "unknown PhiState!");
|
|
assert(NewInsertedDefs.count(base) &&
|
|
"should have already added this in a prev. iteration!");
|
|
}
|
|
|
|
// In essense this assert states: the only way two
|
|
// values incoming from the same basic block may be
|
|
// different is by being different bitcasts of the same
|
|
// value. A cleanup that remains TODO is changing
|
|
// findBaseOrBDV to return an llvm::Value of the correct
|
|
// type (and still remain pure). This will remove the
|
|
// need to add bitcasts.
|
|
assert(base->stripPointerCasts() == oldBase->stripPointerCasts() &&
|
|
"sanity -- findBaseOrBDV should be pure!");
|
|
#endif
|
|
continue;
|
|
}
|
|
|
|
// Find either the defining value for the PHI or the normal base for
|
|
// a non-phi node
|
|
Value *base = findBaseOrBDV(InVal, cache);
|
|
if (!isKnownBaseResult(base)) {
|
|
// Either conflict or base.
|
|
assert(states.count(base));
|
|
base = states[base].getBase();
|
|
assert(base != nullptr && "unknown PhiState!");
|
|
}
|
|
assert(base && "can't be null");
|
|
// Must use original input BB since base may not be Instruction
|
|
// The cast is needed since base traversal may strip away bitcasts
|
|
if (base->getType() != basephi->getType()) {
|
|
base = new BitCastInst(base, basephi->getType(), "cast",
|
|
InBB->getTerminator());
|
|
NewInsertedDefs.insert(base);
|
|
}
|
|
basephi->addIncoming(base, InBB);
|
|
}
|
|
assert(basephi->getNumIncomingValues() == NumPHIValues);
|
|
} else {
|
|
SelectInst *basesel = cast<SelectInst>(state.getBase());
|
|
SelectInst *sel = cast<SelectInst>(v);
|
|
// Operand 1 & 2 are true, false path respectively. TODO: refactor to
|
|
// something more safe and less hacky.
|
|
for (int i = 1; i <= 2; i++) {
|
|
Value *InVal = sel->getOperand(i);
|
|
// Find either the defining value for the PHI or the normal base for
|
|
// a non-phi node
|
|
Value *base = findBaseOrBDV(InVal, cache);
|
|
if (!isKnownBaseResult(base)) {
|
|
// Either conflict or base.
|
|
assert(states.count(base));
|
|
base = states[base].getBase();
|
|
assert(base != nullptr && "unknown PhiState!");
|
|
}
|
|
assert(base && "can't be null");
|
|
// Must use original input BB since base may not be Instruction
|
|
// The cast is needed since base traversal may strip away bitcasts
|
|
if (base->getType() != basesel->getType()) {
|
|
base = new BitCastInst(base, basesel->getType(), "cast", basesel);
|
|
NewInsertedDefs.insert(base);
|
|
}
|
|
basesel->setOperand(i, base);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Cache all of our results so we can cheaply reuse them
|
|
// NOTE: This is actually two caches: one of the base defining value
|
|
// relation and one of the base pointer relation! FIXME
|
|
for (auto item : states) {
|
|
Value *v = item.first;
|
|
Value *base = item.second.getBase();
|
|
assert(v && base);
|
|
assert(!isKnownBaseResult(v) && "why did it get added?");
|
|
|
|
if (TraceLSP) {
|
|
std::string fromstr =
|
|
cache.count(v) ? (cache[v]->hasName() ? cache[v]->getName() : "")
|
|
: "none";
|
|
errs() << "Updating base value cache"
|
|
<< " for: " << (v->hasName() ? v->getName() : "")
|
|
<< " from: " << fromstr
|
|
<< " to: " << (base->hasName() ? base->getName() : "") << "\n";
|
|
}
|
|
|
|
assert(isKnownBaseResult(base) &&
|
|
"must be something we 'know' is a base pointer");
|
|
if (cache.count(v)) {
|
|
// Once we transition from the BDV relation being store in the cache to
|
|
// the base relation being stored, it must be stable
|
|
assert((!isKnownBaseResult(cache[v]) || cache[v] == base) &&
|
|
"base relation should be stable");
|
|
}
|
|
cache[v] = base;
|
|
}
|
|
assert(cache.find(def) != cache.end());
|
|
return cache[def];
|
|
}
|
|
|
|
// For a set of live pointers (base and/or derived), identify the base
|
|
// pointer of the object which they are derived from. This routine will
|
|
// mutate the IR graph as needed to make the 'base' pointer live at the
|
|
// definition site of 'derived'. This ensures that any use of 'derived' can
|
|
// also use 'base'. This may involve the insertion of a number of
|
|
// additional PHI nodes.
|
|
//
|
|
// preconditions: live is a set of pointer type Values
|
|
//
|
|
// side effects: may insert PHI nodes into the existing CFG, will preserve
|
|
// CFG, will not remove or mutate any existing nodes
|
|
//
|
|
// post condition: PointerToBase contains one (derived, base) pair for every
|
|
// pointer in live. Note that derived can be equal to base if the original
|
|
// pointer was a base pointer.
|
|
static void findBasePointers(const StatepointLiveSetTy &live,
|
|
DenseMap<llvm::Value *, llvm::Value *> &PointerToBase,
|
|
DominatorTree *DT, DefiningValueMapTy &DVCache,
|
|
DenseSet<llvm::Value *> &NewInsertedDefs) {
|
|
// For the naming of values inserted to be deterministic - which makes for
|
|
// much cleaner and more stable tests - we need to assign an order to the
|
|
// live values. DenseSets do not provide a deterministic order across runs.
|
|
SmallVector<Value*, 64> Temp;
|
|
Temp.insert(Temp.end(), live.begin(), live.end());
|
|
std::sort(Temp.begin(), Temp.end(), order_by_name);
|
|
for (Value *ptr : Temp) {
|
|
Value *base = findBasePointer(ptr, DVCache, NewInsertedDefs);
|
|
assert(base && "failed to find base pointer");
|
|
PointerToBase[ptr] = base;
|
|
assert((!isa<Instruction>(base) || !isa<Instruction>(ptr) ||
|
|
DT->dominates(cast<Instruction>(base)->getParent(),
|
|
cast<Instruction>(ptr)->getParent())) &&
|
|
"The base we found better dominate the derived pointer");
|
|
|
|
// If you see this trip and like to live really dangerously, the code should
|
|
// be correct, just with idioms the verifier can't handle. You can try
|
|
// disabling the verifier at your own substaintial risk.
|
|
assert(!isNullConstant(base) && "the relocation code needs adjustment to "
|
|
"handle the relocation of a null pointer "
|
|
"constant without causing false positives "
|
|
"in the safepoint ir verifier.");
|
|
}
|
|
}
|
|
|
|
/// Find the required based pointers (and adjust the live set) for the given
|
|
/// parse point.
|
|
static void findBasePointers(DominatorTree &DT, DefiningValueMapTy &DVCache,
|
|
const CallSite &CS,
|
|
PartiallyConstructedSafepointRecord &result) {
|
|
DenseMap<llvm::Value *, llvm::Value *> PointerToBase;
|
|
DenseSet<llvm::Value *> NewInsertedDefs;
|
|
findBasePointers(result.liveset, PointerToBase, &DT, DVCache, NewInsertedDefs);
|
|
|
|
if (PrintBasePointers) {
|
|
// Note: Need to print these in a stable order since this is checked in
|
|
// some tests.
|
|
errs() << "Base Pairs (w/o Relocation):\n";
|
|
SmallVector<Value*, 64> Temp;
|
|
Temp.reserve(PointerToBase.size());
|
|
for (auto Pair : PointerToBase) {
|
|
Temp.push_back(Pair.first);
|
|
}
|
|
std::sort(Temp.begin(), Temp.end(), order_by_name);
|
|
for (Value *Ptr : Temp) {
|
|
Value *Base = PointerToBase[Ptr];
|
|
errs() << " derived %" << Ptr->getName() << " base %"
|
|
<< Base->getName() << "\n";
|
|
}
|
|
}
|
|
|
|
result.PointerToBase = PointerToBase;
|
|
result.NewInsertedDefs = NewInsertedDefs;
|
|
}
|
|
|
|
/// Check for liveness of items in the insert defs and add them to the live
|
|
/// and base pointer sets
|
|
static void fixupLiveness(DominatorTree &DT, const CallSite &CS,
|
|
const DenseSet<Value *> &allInsertedDefs,
|
|
PartiallyConstructedSafepointRecord &result) {
|
|
Instruction *inst = CS.getInstruction();
|
|
|
|
auto liveset = result.liveset;
|
|
auto PointerToBase = result.PointerToBase;
|
|
|
|
auto is_live_gc_reference =
|
|
[&](Value &V) { return isLiveGCReferenceAt(V, inst, DT, nullptr); };
|
|
|
|
// For each new definition, check to see if a) the definition dominates the
|
|
// instruction we're interested in, and b) one of the uses of that definition
|
|
// is edge-reachable from the instruction we're interested in. This is the
|
|
// same definition of liveness we used in the intial liveness analysis
|
|
for (Value *newDef : allInsertedDefs) {
|
|
if (liveset.count(newDef)) {
|
|
// already live, no action needed
|
|
continue;
|
|
}
|
|
|
|
// PERF: Use DT to check instruction domination might not be good for
|
|
// compilation time, and we could change to optimal solution if this
|
|
// turn to be a issue
|
|
if (!DT.dominates(cast<Instruction>(newDef), inst)) {
|
|
// can't possibly be live at inst
|
|
continue;
|
|
}
|
|
|
|
if (is_live_gc_reference(*newDef)) {
|
|
// Add the live new defs into liveset and PointerToBase
|
|
liveset.insert(newDef);
|
|
PointerToBase[newDef] = newDef;
|
|
}
|
|
}
|
|
|
|
result.liveset = liveset;
|
|
result.PointerToBase = PointerToBase;
|
|
}
|
|
|
|
static void fixupLiveReferences(
|
|
Function &F, DominatorTree &DT, Pass *P,
|
|
const DenseSet<llvm::Value *> &allInsertedDefs,
|
|
ArrayRef<CallSite> toUpdate,
|
|
MutableArrayRef<struct PartiallyConstructedSafepointRecord> records) {
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
const CallSite &CS = toUpdate[i];
|
|
fixupLiveness(DT, CS, allInsertedDefs, info);
|
|
}
|
|
}
|
|
|
|
// 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,
|
|
Pass *P) {
|
|
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;
|
|
}
|
|
|
|
static int find_index(ArrayRef<Value *> livevec, Value *val) {
|
|
auto itr = std::find(livevec.begin(), livevec.end(), val);
|
|
assert(livevec.end() != itr);
|
|
size_t index = std::distance(livevec.begin(), itr);
|
|
assert(index < livevec.size());
|
|
return index;
|
|
}
|
|
|
|
// Create new attribute set containing only attributes which can be transfered
|
|
// from original call to the safepoint.
|
|
static AttributeSet legalizeCallAttributes(AttributeSet AS) {
|
|
AttributeSet ret;
|
|
|
|
for (unsigned Slot = 0; Slot < AS.getNumSlots(); Slot++) {
|
|
unsigned index = AS.getSlotIndex(Slot);
|
|
|
|
if (index == AttributeSet::ReturnIndex ||
|
|
index == AttributeSet::FunctionIndex) {
|
|
|
|
for (auto it = AS.begin(Slot), it_end = AS.end(Slot); it != it_end;
|
|
++it) {
|
|
Attribute attr = *it;
|
|
|
|
// Do not allow certain attributes - just skip them
|
|
// Safepoint can not be read only or read none.
|
|
if (attr.hasAttribute(Attribute::ReadNone) ||
|
|
attr.hasAttribute(Attribute::ReadOnly))
|
|
continue;
|
|
|
|
ret = ret.addAttributes(
|
|
AS.getContext(), index,
|
|
AttributeSet::get(AS.getContext(), index, AttrBuilder(attr)));
|
|
}
|
|
}
|
|
|
|
// Just skip parameter attributes for now
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/// Helper function to place all gc relocates necessary for the given
|
|
/// statepoint.
|
|
/// Inputs:
|
|
/// liveVariables - list of variables to be relocated.
|
|
/// liveStart - index of the first live variable.
|
|
/// basePtrs - base pointers.
|
|
/// statepointToken - statepoint instruction to which relocates should be
|
|
/// bound.
|
|
/// Builder - Llvm IR builder to be used to construct new calls.
|
|
static void CreateGCRelocates(ArrayRef<llvm::Value *> liveVariables,
|
|
const int liveStart,
|
|
ArrayRef<llvm::Value *> basePtrs,
|
|
Instruction *statepointToken,
|
|
IRBuilder<> Builder) {
|
|
SmallVector<Instruction *, 64> NewDefs;
|
|
NewDefs.reserve(liveVariables.size());
|
|
|
|
Module *M = statepointToken->getParent()->getParent()->getParent();
|
|
|
|
for (unsigned i = 0; i < liveVariables.size(); i++) {
|
|
// We generate a (potentially) unique declaration for every pointer type
|
|
// combination. This results is some blow up the function declarations in
|
|
// the IR, but removes the need for argument bitcasts which shrinks the IR
|
|
// greatly and makes it much more readable.
|
|
SmallVector<Type *, 1> types; // one per 'any' type
|
|
types.push_back(liveVariables[i]->getType()); // result type
|
|
Value *gc_relocate_decl = Intrinsic::getDeclaration(
|
|
M, Intrinsic::experimental_gc_relocate, types);
|
|
|
|
// Generate the gc.relocate call and save the result
|
|
Value *baseIdx =
|
|
ConstantInt::get(Type::getInt32Ty(M->getContext()),
|
|
liveStart + find_index(liveVariables, basePtrs[i]));
|
|
Value *liveIdx = ConstantInt::get(
|
|
Type::getInt32Ty(M->getContext()),
|
|
liveStart + find_index(liveVariables, liveVariables[i]));
|
|
|
|
// only specify a debug name if we can give a useful one
|
|
Value *reloc = Builder.CreateCall3(
|
|
gc_relocate_decl, statepointToken, baseIdx, liveIdx,
|
|
liveVariables[i]->hasName() ? liveVariables[i]->getName() + ".relocated"
|
|
: "");
|
|
// Trick CodeGen into thinking there are lots of free registers at this
|
|
// fake call.
|
|
cast<CallInst>(reloc)->setCallingConv(CallingConv::Cold);
|
|
|
|
NewDefs.push_back(cast<Instruction>(reloc));
|
|
}
|
|
assert(NewDefs.size() == liveVariables.size() &&
|
|
"missing or extra redefinition at safepoint");
|
|
}
|
|
|
|
static void
|
|
makeStatepointExplicitImpl(const CallSite &CS, /* to replace */
|
|
const SmallVectorImpl<llvm::Value *> &basePtrs,
|
|
const SmallVectorImpl<llvm::Value *> &liveVariables,
|
|
Pass *P,
|
|
PartiallyConstructedSafepointRecord &result) {
|
|
assert(basePtrs.size() == liveVariables.size());
|
|
assert(isStatepoint(CS) &&
|
|
"This method expects to be rewriting a statepoint");
|
|
|
|
BasicBlock *BB = CS.getInstruction()->getParent();
|
|
assert(BB);
|
|
Function *F = BB->getParent();
|
|
assert(F && "must be set");
|
|
Module *M = F->getParent();
|
|
(void)M;
|
|
assert(M && "must be set");
|
|
|
|
// We're not changing the function signature of the statepoint since the gc
|
|
// arguments go into the var args section.
|
|
Function *gc_statepoint_decl = CS.getCalledFunction();
|
|
|
|
// 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);
|
|
// Copy all of the arguments from the original statepoint - this includes the
|
|
// target, call args, and deopt args
|
|
SmallVector<llvm::Value *, 64> args;
|
|
args.insert(args.end(), CS.arg_begin(), CS.arg_end());
|
|
// TODO: Clear the 'needs rewrite' flag
|
|
|
|
// add all the pointers to be relocated (gc arguments)
|
|
// Capture the start of the live variable list for use in the gc_relocates
|
|
const int live_start = args.size();
|
|
args.insert(args.end(), liveVariables.begin(), liveVariables.end());
|
|
|
|
// 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());
|
|
|
|
// Currently we will fail on parameter attributes and on certain
|
|
// function attributes.
|
|
AttributeSet new_attrs = legalizeCallAttributes(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();
|
|
|
|
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());
|
|
|
|
} else {
|
|
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());
|
|
|
|
// Currently we will fail on parameter attributes and on certain
|
|
// function attributes.
|
|
AttributeSet new_attrs = legalizeCallAttributes(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();
|
|
|
|
token = invoke;
|
|
|
|
// Generate gc relocates in exceptional path
|
|
BasicBlock *unwindBlock = normalizeBBForInvokeSafepoint(
|
|
toReplace->getUnwindDest(), invoke->getParent(), P);
|
|
|
|
Instruction *IP = &*(unwindBlock->getFirstInsertionPt());
|
|
Builder.SetInsertPoint(IP);
|
|
Builder.SetCurrentDebugLocation(toReplace->getDebugLoc());
|
|
|
|
// Extract second element from landingpad return value. We will attach
|
|
// exceptional gc relocates to it.
|
|
const unsigned idx = 1;
|
|
Instruction *exceptional_token =
|
|
cast<Instruction>(Builder.CreateExtractValue(
|
|
unwindBlock->getLandingPadInst(), idx, "relocate_token"));
|
|
result.UnwindToken = exceptional_token;
|
|
|
|
// Just throw away return value. We will use the one we got for normal
|
|
// block.
|
|
(void)CreateGCRelocates(liveVariables, live_start, basePtrs,
|
|
exceptional_token, Builder);
|
|
|
|
// Generate gc relocates and returns for normal block
|
|
BasicBlock *normalDest = normalizeBBForInvokeSafepoint(
|
|
toReplace->getNormalDest(), invoke->getParent(), P);
|
|
|
|
IP = &*(normalDest->getFirstInsertionPt());
|
|
Builder.SetInsertPoint(IP);
|
|
|
|
// gc relocates will be generated later as if it were regular call
|
|
// statepoint
|
|
}
|
|
assert(token);
|
|
|
|
// Take the name of the original value call if it had one.
|
|
token->takeName(CS.getInstruction());
|
|
|
|
// The GCResult is already inserted, we just need to find it
|
|
#ifndef NDEBUG
|
|
Instruction *toReplace = CS.getInstruction();
|
|
assert((toReplace->hasNUses(0) || toReplace->hasNUses(1)) &&
|
|
"only valid use before rewrite is gc.result");
|
|
assert(!toReplace->hasOneUse() ||
|
|
isGCResult(cast<Instruction>(*toReplace->user_begin())));
|
|
#endif
|
|
|
|
// Update the gc.result of the original statepoint (if any) to use the newly
|
|
// inserted statepoint. This is safe to do here since the token can't be
|
|
// considered a live reference.
|
|
CS.getInstruction()->replaceAllUsesWith(token);
|
|
|
|
result.StatepointToken = token;
|
|
|
|
// Second, create a gc.relocate for every live variable
|
|
CreateGCRelocates(liveVariables, live_start, basePtrs, token, Builder);
|
|
|
|
}
|
|
|
|
namespace {
|
|
struct name_ordering {
|
|
Value *base;
|
|
Value *derived;
|
|
bool operator()(name_ordering const &a, name_ordering const &b) {
|
|
return -1 == a.derived->getName().compare(b.derived->getName());
|
|
}
|
|
};
|
|
}
|
|
static void stablize_order(SmallVectorImpl<Value *> &basevec,
|
|
SmallVectorImpl<Value *> &livevec) {
|
|
assert(basevec.size() == livevec.size());
|
|
|
|
SmallVector<name_ordering, 64> temp;
|
|
for (size_t i = 0; i < basevec.size(); i++) {
|
|
name_ordering v;
|
|
v.base = basevec[i];
|
|
v.derived = livevec[i];
|
|
temp.push_back(v);
|
|
}
|
|
std::sort(temp.begin(), temp.end(), name_ordering());
|
|
for (size_t i = 0; i < basevec.size(); i++) {
|
|
basevec[i] = temp[i].base;
|
|
livevec[i] = temp[i].derived;
|
|
}
|
|
}
|
|
|
|
// Replace an existing gc.statepoint with a new one and a set of gc.relocates
|
|
// which make the relocations happening at this safepoint explicit.
|
|
//
|
|
// WARNING: Does not do any fixup to adjust users of the original live
|
|
// values. That's the callers responsibility.
|
|
static void
|
|
makeStatepointExplicit(DominatorTree &DT, const CallSite &CS, Pass *P,
|
|
PartiallyConstructedSafepointRecord &result) {
|
|
auto liveset = result.liveset;
|
|
auto PointerToBase = result.PointerToBase;
|
|
|
|
// Convert to vector for efficient cross referencing.
|
|
SmallVector<Value *, 64> basevec, livevec;
|
|
livevec.reserve(liveset.size());
|
|
basevec.reserve(liveset.size());
|
|
for (Value *L : liveset) {
|
|
livevec.push_back(L);
|
|
|
|
assert(PointerToBase.find(L) != PointerToBase.end());
|
|
Value *base = PointerToBase[L];
|
|
basevec.push_back(base);
|
|
}
|
|
assert(livevec.size() == basevec.size());
|
|
|
|
// To make the output IR slightly more stable (for use in diffs), ensure a
|
|
// fixed order of the values in the safepoint (by sorting the value name).
|
|
// The order is otherwise meaningless.
|
|
stablize_order(basevec, livevec);
|
|
|
|
// Do the actual rewriting and delete the old statepoint
|
|
makeStatepointExplicitImpl(CS, basevec, livevec, P, result);
|
|
CS.getInstruction()->eraseFromParent();
|
|
}
|
|
|
|
// Helper function for the relocationViaAlloca.
|
|
// It receives iterator to the statepoint gc relocates and emits store to the
|
|
// assigned
|
|
// location (via allocaMap) for the each one of them.
|
|
// Add visited values into the visitedLiveValues set we will later use them
|
|
// for sanity check.
|
|
static void
|
|
insertRelocationStores(iterator_range<Value::user_iterator> gcRelocs,
|
|
DenseMap<Value *, Value *> &allocaMap,
|
|
DenseSet<Value *> &visitedLiveValues) {
|
|
|
|
for (User *U : gcRelocs) {
|
|
if (!isa<IntrinsicInst>(U))
|
|
continue;
|
|
|
|
IntrinsicInst *relocatedValue = cast<IntrinsicInst>(U);
|
|
|
|
// We only care about relocates
|
|
if (relocatedValue->getIntrinsicID() !=
|
|
Intrinsic::experimental_gc_relocate) {
|
|
continue;
|
|
}
|
|
|
|
GCRelocateOperands relocateOperands(relocatedValue);
|
|
Value *originalValue = const_cast<Value *>(relocateOperands.derivedPtr());
|
|
assert(allocaMap.count(originalValue));
|
|
Value *alloca = allocaMap[originalValue];
|
|
|
|
// Emit store into the related alloca
|
|
StoreInst *store = new StoreInst(relocatedValue, alloca);
|
|
store->insertAfter(relocatedValue);
|
|
|
|
#ifndef NDEBUG
|
|
visitedLiveValues.insert(originalValue);
|
|
#endif
|
|
}
|
|
}
|
|
|
|
/// do all the relocation update via allocas and mem2reg
|
|
static void relocationViaAlloca(
|
|
Function &F, DominatorTree &DT, ArrayRef<Value *> live,
|
|
ArrayRef<struct PartiallyConstructedSafepointRecord> records) {
|
|
#ifndef NDEBUG
|
|
int initialAllocaNum = 0;
|
|
|
|
// record initial number of allocas
|
|
for (inst_iterator itr = inst_begin(F), end = inst_end(F); itr != end;
|
|
itr++) {
|
|
if (isa<AllocaInst>(*itr))
|
|
initialAllocaNum++;
|
|
}
|
|
#endif
|
|
|
|
// TODO-PERF: change data structures, reserve
|
|
DenseMap<Value *, Value *> allocaMap;
|
|
SmallVector<AllocaInst *, 200> PromotableAllocas;
|
|
PromotableAllocas.reserve(live.size());
|
|
|
|
// emit alloca for each live gc pointer
|
|
for (unsigned i = 0; i < live.size(); i++) {
|
|
Value *liveValue = live[i];
|
|
AllocaInst *alloca = new AllocaInst(liveValue->getType(), "",
|
|
F.getEntryBlock().getFirstNonPHI());
|
|
allocaMap[liveValue] = alloca;
|
|
PromotableAllocas.push_back(alloca);
|
|
}
|
|
|
|
// The next two loops are part of the same conceptual operation. We need to
|
|
// insert a store to the alloca after the original def and at each
|
|
// redefinition. We need to insert a load before each use. These are split
|
|
// into distinct loops for performance reasons.
|
|
|
|
// update gc pointer after each statepoint
|
|
// either store a relocated value or null (if no relocated value found for
|
|
// this gc pointer and it is not a gc_result)
|
|
// this must happen before we update the statepoint with load of alloca
|
|
// otherwise we lose the link between statepoint and old def
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
const struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
Value *Statepoint = info.StatepointToken;
|
|
|
|
// This will be used for consistency check
|
|
DenseSet<Value *> visitedLiveValues;
|
|
|
|
// Insert stores for normal statepoint gc relocates
|
|
insertRelocationStores(Statepoint->users(), allocaMap, visitedLiveValues);
|
|
|
|
// In case if it was invoke statepoint
|
|
// we will insert stores for exceptional path gc relocates.
|
|
if (isa<InvokeInst>(Statepoint)) {
|
|
insertRelocationStores(info.UnwindToken->users(),
|
|
allocaMap, visitedLiveValues);
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
// As a debuging aid, pretend that an unrelocated pointer becomes null at
|
|
// the gc.statepoint. This will turn some subtle GC problems into slightly
|
|
// easier to debug SEGVs
|
|
SmallVector<AllocaInst *, 64> ToClobber;
|
|
for (auto Pair : allocaMap) {
|
|
Value *Def = Pair.first;
|
|
AllocaInst *Alloca = cast<AllocaInst>(Pair.second);
|
|
|
|
// This value was relocated
|
|
if (visitedLiveValues.count(Def)) {
|
|
continue;
|
|
}
|
|
ToClobber.push_back(Alloca);
|
|
}
|
|
|
|
auto InsertClobbersAt = [&](Instruction *IP) {
|
|
for (auto *AI : ToClobber) {
|
|
auto AIType = cast<PointerType>(AI->getType());
|
|
auto PT = cast<PointerType>(AIType->getElementType());
|
|
Constant *CPN = ConstantPointerNull::get(PT);
|
|
StoreInst *store = new StoreInst(CPN, AI);
|
|
store->insertBefore(IP);
|
|
}
|
|
};
|
|
|
|
// Insert the clobbering stores. These may get intermixed with the
|
|
// gc.results and gc.relocates, but that's fine.
|
|
if (auto II = dyn_cast<InvokeInst>(Statepoint)) {
|
|
InsertClobbersAt(II->getNormalDest()->getFirstInsertionPt());
|
|
InsertClobbersAt(II->getUnwindDest()->getFirstInsertionPt());
|
|
} else {
|
|
BasicBlock::iterator Next(cast<CallInst>(Statepoint));
|
|
Next++;
|
|
InsertClobbersAt(Next);
|
|
}
|
|
#endif
|
|
}
|
|
// update use with load allocas and add store for gc_relocated
|
|
for (auto Pair : allocaMap) {
|
|
Value *def = Pair.first;
|
|
Value *alloca = Pair.second;
|
|
|
|
// we pre-record the uses of allocas so that we dont have to worry about
|
|
// later update
|
|
// that change the user information.
|
|
SmallVector<Instruction *, 20> uses;
|
|
// PERF: trade a linear scan for repeated reallocation
|
|
uses.reserve(std::distance(def->user_begin(), def->user_end()));
|
|
for (User *U : def->users()) {
|
|
if (!isa<ConstantExpr>(U)) {
|
|
// If the def has a ConstantExpr use, then the def is either a
|
|
// ConstantExpr use itself or null. In either case
|
|
// (recursively in the first, directly in the second), the oop
|
|
// it is ultimately dependent on is null and this particular
|
|
// use does not need to be fixed up.
|
|
uses.push_back(cast<Instruction>(U));
|
|
}
|
|
}
|
|
|
|
std::sort(uses.begin(), uses.end());
|
|
auto last = std::unique(uses.begin(), uses.end());
|
|
uses.erase(last, uses.end());
|
|
|
|
for (Instruction *use : uses) {
|
|
if (isa<PHINode>(use)) {
|
|
PHINode *phi = cast<PHINode>(use);
|
|
for (unsigned i = 0; i < phi->getNumIncomingValues(); i++) {
|
|
if (def == phi->getIncomingValue(i)) {
|
|
LoadInst *load = new LoadInst(
|
|
alloca, "", phi->getIncomingBlock(i)->getTerminator());
|
|
phi->setIncomingValue(i, load);
|
|
}
|
|
}
|
|
} else {
|
|
LoadInst *load = new LoadInst(alloca, "", use);
|
|
use->replaceUsesOfWith(def, load);
|
|
}
|
|
}
|
|
|
|
// emit store for the initial gc value
|
|
// store must be inserted after load, otherwise store will be in alloca's
|
|
// use list and an extra load will be inserted before it
|
|
StoreInst *store = new StoreInst(def, alloca);
|
|
if (Instruction *inst = dyn_cast<Instruction>(def)) {
|
|
if (InvokeInst *invoke = dyn_cast<InvokeInst>(inst)) {
|
|
// InvokeInst is a TerminatorInst so the store need to be inserted
|
|
// into its normal destination block.
|
|
BasicBlock *normalDest = invoke->getNormalDest();
|
|
store->insertBefore(normalDest->getFirstNonPHI());
|
|
} else {
|
|
assert(!inst->isTerminator() &&
|
|
"The only TerminatorInst that can produce a value is "
|
|
"InvokeInst which is handled above.");
|
|
store->insertAfter(inst);
|
|
}
|
|
} else {
|
|
assert((isa<Argument>(def) || isa<GlobalVariable>(def) ||
|
|
(isa<Constant>(def) && cast<Constant>(def)->isNullValue())) &&
|
|
"Must be argument or global");
|
|
store->insertAfter(cast<Instruction>(alloca));
|
|
}
|
|
}
|
|
|
|
assert(PromotableAllocas.size() == live.size() &&
|
|
"we must have the same allocas with lives");
|
|
if (!PromotableAllocas.empty()) {
|
|
// apply mem2reg to promote alloca to SSA
|
|
PromoteMemToReg(PromotableAllocas, DT);
|
|
}
|
|
|
|
#ifndef NDEBUG
|
|
for (inst_iterator itr = inst_begin(F), end = inst_end(F); itr != end;
|
|
itr++) {
|
|
if (isa<AllocaInst>(*itr))
|
|
initialAllocaNum--;
|
|
}
|
|
assert(initialAllocaNum == 0 && "We must not introduce any extra allocas");
|
|
#endif
|
|
}
|
|
|
|
/// Implement a unique function which doesn't require we sort the input
|
|
/// vector. Doing so has the effect of changing the output of a couple of
|
|
/// tests in ways which make them less useful in testing fused safepoints.
|
|
template <typename T> static void unique_unsorted(SmallVectorImpl<T> &Vec) {
|
|
DenseSet<T> Seen;
|
|
SmallVector<T, 128> TempVec;
|
|
TempVec.reserve(Vec.size());
|
|
for (auto Element : Vec)
|
|
TempVec.push_back(Element);
|
|
Vec.clear();
|
|
for (auto V : TempVec) {
|
|
if (Seen.insert(V).second) {
|
|
Vec.push_back(V);
|
|
}
|
|
}
|
|
}
|
|
|
|
static Function *getUseHolder(Module &M) {
|
|
FunctionType *ftype =
|
|
FunctionType::get(Type::getVoidTy(M.getContext()), true);
|
|
Function *Func = cast<Function>(M.getOrInsertFunction("__tmp_use", ftype));
|
|
return Func;
|
|
}
|
|
|
|
/// Insert holders so that each Value is obviously live through the entire
|
|
/// liftetime of the call.
|
|
static void insertUseHolderAfter(CallSite &CS, const ArrayRef<Value *> Values,
|
|
SmallVectorImpl<CallInst *> &holders) {
|
|
Module *M = CS.getInstruction()->getParent()->getParent()->getParent();
|
|
Function *Func = getUseHolder(*M);
|
|
if (CS.isCall()) {
|
|
// For call safepoints insert dummy calls right after safepoint
|
|
BasicBlock::iterator next(CS.getInstruction());
|
|
next++;
|
|
CallInst *base_holder = CallInst::Create(Func, Values, "", next);
|
|
holders.push_back(base_holder);
|
|
} else if (CS.isInvoke()) {
|
|
// For invoke safepooints insert dummy calls both in normal and
|
|
// exceptional destination blocks
|
|
InvokeInst *invoke = cast<InvokeInst>(CS.getInstruction());
|
|
CallInst *normal_holder = CallInst::Create(
|
|
Func, Values, "", invoke->getNormalDest()->getFirstInsertionPt());
|
|
CallInst *unwind_holder = CallInst::Create(
|
|
Func, Values, "", invoke->getUnwindDest()->getFirstInsertionPt());
|
|
holders.push_back(normal_holder);
|
|
holders.push_back(unwind_holder);
|
|
} else
|
|
llvm_unreachable("unsupported call type");
|
|
}
|
|
|
|
static void findLiveReferences(
|
|
Function &F, DominatorTree &DT, Pass *P, ArrayRef<CallSite> toUpdate,
|
|
MutableArrayRef<struct PartiallyConstructedSafepointRecord> records) {
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
const CallSite &CS = toUpdate[i];
|
|
analyzeParsePointLiveness(DT, CS, info);
|
|
}
|
|
}
|
|
|
|
static void addBasesAsLiveValues(StatepointLiveSetTy &liveset,
|
|
DenseMap<Value *, Value *> &PointerToBase) {
|
|
// Identify any base pointers which are used in this safepoint, but not
|
|
// themselves relocated. We need to relocate them so that later inserted
|
|
// safepoints can get the properly relocated base register.
|
|
DenseSet<Value *> missing;
|
|
for (Value *L : liveset) {
|
|
assert(PointerToBase.find(L) != PointerToBase.end());
|
|
Value *base = PointerToBase[L];
|
|
assert(base);
|
|
if (liveset.find(base) == liveset.end()) {
|
|
assert(PointerToBase.find(base) == PointerToBase.end());
|
|
// uniqued by set insert
|
|
missing.insert(base);
|
|
}
|
|
}
|
|
|
|
// Note that we want these at the end of the list, otherwise
|
|
// register placement gets screwed up once we lower to STATEPOINT
|
|
// instructions. This is an utter hack, but there doesn't seem to be a
|
|
// better one.
|
|
for (Value *base : missing) {
|
|
assert(base);
|
|
liveset.insert(base);
|
|
PointerToBase[base] = base;
|
|
}
|
|
assert(liveset.size() == PointerToBase.size());
|
|
}
|
|
|
|
static bool insertParsePoints(Function &F, DominatorTree &DT, Pass *P,
|
|
SmallVectorImpl<CallSite> &toUpdate) {
|
|
#ifndef NDEBUG
|
|
// sanity check the input
|
|
std::set<CallSite> uniqued;
|
|
uniqued.insert(toUpdate.begin(), toUpdate.end());
|
|
assert(uniqued.size() == toUpdate.size() && "no duplicates please!");
|
|
|
|
for (size_t i = 0; i < toUpdate.size(); i++) {
|
|
CallSite &CS = toUpdate[i];
|
|
assert(CS.getInstruction()->getParent()->getParent() == &F);
|
|
assert(isStatepoint(CS) && "expected to already be a deopt statepoint");
|
|
}
|
|
#endif
|
|
|
|
// A list of dummy calls added to the IR to keep various values obviously
|
|
// live in the IR. We'll remove all of these when done.
|
|
SmallVector<CallInst *, 64> holders;
|
|
|
|
// Insert a dummy call with all of the arguments to the vm_state we'll need
|
|
// for the actual safepoint insertion. This ensures reference arguments in
|
|
// the deopt argument list are considered live through the safepoint (and
|
|
// thus makes sure they get relocated.)
|
|
for (size_t i = 0; i < toUpdate.size(); i++) {
|
|
CallSite &CS = toUpdate[i];
|
|
Statepoint StatepointCS(CS);
|
|
|
|
SmallVector<Value *, 64> DeoptValues;
|
|
for (Use &U : StatepointCS.vm_state_args()) {
|
|
Value *Arg = cast<Value>(&U);
|
|
if (isGCPointerType(Arg->getType()))
|
|
DeoptValues.push_back(Arg);
|
|
}
|
|
insertUseHolderAfter(CS, DeoptValues, holders);
|
|
}
|
|
|
|
SmallVector<struct PartiallyConstructedSafepointRecord, 64> records;
|
|
records.reserve(toUpdate.size());
|
|
for (size_t i = 0; i < toUpdate.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord info;
|
|
records.push_back(info);
|
|
}
|
|
assert(records.size() == toUpdate.size());
|
|
|
|
// A) Identify all gc pointers which are staticly live at the given call
|
|
// site.
|
|
findLiveReferences(F, DT, P, toUpdate, records);
|
|
|
|
// B) Find the base pointers for each live pointer
|
|
/* scope for caching */ {
|
|
// Cache the 'defining value' relation used in the computation and
|
|
// insertion of base phis and selects. This ensures that we don't insert
|
|
// large numbers of duplicate base_phis.
|
|
DefiningValueMapTy DVCache;
|
|
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
CallSite &CS = toUpdate[i];
|
|
findBasePointers(DT, DVCache, CS, info);
|
|
}
|
|
} // end of cache scope
|
|
|
|
// The base phi insertion logic (for any safepoint) may have inserted new
|
|
// instructions which are now live at some safepoint. The simplest such
|
|
// example is:
|
|
// loop:
|
|
// phi a <-- will be a new base_phi here
|
|
// safepoint 1 <-- that needs to be live here
|
|
// gep a + 1
|
|
// safepoint 2
|
|
// br loop
|
|
DenseSet<llvm::Value *> allInsertedDefs;
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
allInsertedDefs.insert(info.NewInsertedDefs.begin(),
|
|
info.NewInsertedDefs.end());
|
|
}
|
|
|
|
// We insert some dummy calls after each safepoint to definitely hold live
|
|
// the base pointers which were identified for that safepoint. We'll then
|
|
// ask liveness for _every_ base inserted to see what is now live. Then we
|
|
// remove the dummy calls.
|
|
holders.reserve(holders.size() + records.size());
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
CallSite &CS = toUpdate[i];
|
|
|
|
SmallVector<Value *, 128> Bases;
|
|
for (auto Pair : info.PointerToBase) {
|
|
Bases.push_back(Pair.second);
|
|
}
|
|
insertUseHolderAfter(CS, Bases, holders);
|
|
}
|
|
|
|
// Add the bases explicitly to the live vector set. This may result in a few
|
|
// extra relocations, but the base has to be available whenever a pointer
|
|
// derived from it is used. Thus, we need it to be part of the statepoint's
|
|
// gc arguments list. TODO: Introduce an explicit notion (in the following
|
|
// code) of the GC argument list as seperate from the live Values at a
|
|
// given statepoint.
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
addBasesAsLiveValues(info.liveset, info.PointerToBase);
|
|
}
|
|
|
|
// If we inserted any new values, we need to adjust our notion of what is
|
|
// live at a particular safepoint.
|
|
if (!allInsertedDefs.empty()) {
|
|
fixupLiveReferences(F, DT, P, allInsertedDefs, toUpdate, records);
|
|
}
|
|
if (PrintBasePointers) {
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
errs() << "Base Pairs: (w/Relocation)\n";
|
|
for (auto Pair : info.PointerToBase) {
|
|
errs() << " derived %" << Pair.first->getName() << " base %"
|
|
<< Pair.second->getName() << "\n";
|
|
}
|
|
}
|
|
}
|
|
for (size_t i = 0; i < holders.size(); i++) {
|
|
holders[i]->eraseFromParent();
|
|
holders[i] = nullptr;
|
|
}
|
|
holders.clear();
|
|
|
|
// Now run through and replace the existing statepoints with new ones with
|
|
// the live variables listed. We do not yet update uses of the values being
|
|
// relocated. We have references to live variables that need to
|
|
// survive to the last iteration of this loop. (By construction, the
|
|
// previous statepoint can not be a live variable, thus we can and remove
|
|
// the old statepoint calls as we go.)
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
CallSite &CS = toUpdate[i];
|
|
makeStatepointExplicit(DT, CS, P, info);
|
|
}
|
|
toUpdate.clear(); // prevent accident use of invalid CallSites
|
|
|
|
// In case if we inserted relocates in a different basic block than the
|
|
// original safepoint (this can happen for invokes). We need to be sure that
|
|
// original values were not used in any of the phi nodes at the
|
|
// beginning of basic block containing them. 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.
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
Instruction *I = records[i].StatepointToken;
|
|
|
|
if (InvokeInst *invoke = dyn_cast<InvokeInst>(I)) {
|
|
FoldSingleEntryPHINodes(invoke->getNormalDest());
|
|
assert(!isa<PHINode>(invoke->getNormalDest()->begin()));
|
|
|
|
FoldSingleEntryPHINodes(invoke->getUnwindDest());
|
|
assert(!isa<PHINode>(invoke->getUnwindDest()->begin()));
|
|
}
|
|
}
|
|
|
|
// Do all the fixups of the original live variables to their relocated selves
|
|
SmallVector<Value *, 128> live;
|
|
for (size_t i = 0; i < records.size(); i++) {
|
|
struct PartiallyConstructedSafepointRecord &info = records[i];
|
|
// We can't simply save the live set from the original insertion. One of
|
|
// the live values might be the result of a call which needs a safepoint.
|
|
// That Value* no longer exists and we need to use the new gc_result.
|
|
// Thankfully, the liveset is embedded in the statepoint (and updated), so
|
|
// we just grab that.
|
|
Statepoint statepoint(info.StatepointToken);
|
|
live.insert(live.end(), statepoint.gc_args_begin(),
|
|
statepoint.gc_args_end());
|
|
}
|
|
unique_unsorted(live);
|
|
|
|
#ifndef NDEBUG
|
|
// sanity check
|
|
for (auto ptr : live) {
|
|
assert(isGCPointerType(ptr->getType()) && "must be a gc pointer type");
|
|
}
|
|
#endif
|
|
|
|
relocationViaAlloca(F, DT, live, records);
|
|
return !records.empty();
|
|
}
|
|
|
|
/// Returns true if this function should be rewritten by this pass. The main
|
|
/// point of this function is as an extension point for custom logic.
|
|
static bool shouldRewriteStatepointsIn(Function &F) {
|
|
// TODO: This should check the GCStrategy
|
|
if (F.hasGC()) {
|
|
const std::string StatepointExampleName("statepoint-example");
|
|
return StatepointExampleName == F.getGC();
|
|
} else
|
|
return false;
|
|
}
|
|
|
|
bool RewriteStatepointsForGC::runOnFunction(Function &F) {
|
|
// Nothing to do for declarations.
|
|
if (F.isDeclaration() || F.empty())
|
|
return false;
|
|
|
|
// Policy choice says not to rewrite - the most common reason is that we're
|
|
// compiling code without a GCStrategy.
|
|
if (!shouldRewriteStatepointsIn(F))
|
|
return false;
|
|
|
|
// Gather all the statepoints which need rewritten.
|
|
SmallVector<CallSite, 64> ParsePointNeeded;
|
|
for (Instruction &I : inst_range(F)) {
|
|
// TODO: only the ones with the flag set!
|
|
if (isStatepoint(I))
|
|
ParsePointNeeded.push_back(CallSite(&I));
|
|
}
|
|
|
|
// Return early if no work to do.
|
|
if (ParsePointNeeded.empty())
|
|
return false;
|
|
|
|
DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
|
|
return insertParsePoints(F, DT, this, ParsePointNeeded);
|
|
}
|