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//===- StatepointLowering.h - SDAGBuilder's statepoint code ---*- C++ -*---===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file includes support code use by SelectionDAGBuilder when lowering a
// statepoint sequence in SelectionDAG IR.
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/IR/IntrinsicInst.h"
#include <cassert>
namespace llvm {
class SelectionDAGBuilder;
/// This class tracks both per-statepoint and per-selectiondag information.
/// For each statepoint it tracks locations of it's gc valuess (incoming and
/// relocated) and list of gcreloc calls scheduled for visiting (this is
/// used for a debug mode consistency check only). The spill slot tracking
/// works in concert with information in FunctionLoweringInfo.
class StatepointLoweringState {
StatepointLoweringState() = default;
/// Reset all state tracking for a newly encountered safepoint. Also
/// performs some consistency checking.
void startNewStatepoint(SelectionDAGBuilder &Builder);
/// Clear the memory usage of this object. This is called from
/// SelectionDAGBuilder::clear. We require this is never called in the
/// midst of processing a statepoint sequence.
void clear();
/// Returns the spill location of a value incoming to the current
/// statepoint. Will return SDValue() if this value hasn't been
/// spilled. Otherwise, the value has already been spilled and no
/// further action is required by the caller.
SDValue getLocation(SDValue Val) {
auto I = Locations.find(Val);
if (I == Locations.end())
return SDValue();
return I->second;
void setLocation(SDValue Val, SDValue Location) {
assert(!Locations.count(Val) &&
"Trying to allocate already allocated location");
Locations[Val] = Location;
/// Record the fact that we expect to encounter a given gc_relocate
/// before the next statepoint. If we don't see it, we'll report
/// an assertion.
void scheduleRelocCall(const GCRelocateInst &RelocCall) {
// We are not interested in lowering dead instructions.
if (!RelocCall.use_empty())
/// Remove this gc_relocate from the list we're expecting to see
/// before the next statepoint. If we weren't expecting to see
/// it, we'll report an assertion.
void relocCallVisited(const GCRelocateInst &RelocCall) {
// We are not interested in lowering dead instructions.
if (RelocCall.use_empty())
auto I = llvm::find(PendingGCRelocateCalls, &RelocCall);
assert(I != PendingGCRelocateCalls.end() &&
"Visited unexpected gcrelocate call");
// TODO: Should add consistency tracking to ensure we encounter
// expected gc_result calls too.
/// Get a stack slot we can use to store an value of type ValueType. This
/// will hopefully be a recylced slot from another statepoint.
SDValue allocateStackSlot(EVT ValueType, SelectionDAGBuilder &Builder);
void reserveStackSlot(int Offset) {
assert(Offset >= 0 && Offset < (int)AllocatedStackSlots.size() &&
"out of bounds");
assert(!AllocatedStackSlots.test(Offset) && "already reserved!");
assert(NextSlotToAllocate <= (unsigned)Offset && "consistency!");
bool isStackSlotAllocated(int Offset) {
assert(Offset >= 0 && Offset < (int)AllocatedStackSlots.size() &&
"out of bounds");
return AllocatedStackSlots.test(Offset);
/// Maps pre-relocation value (gc pointer directly incoming into statepoint)
/// into it's location (currently only stack slots)
DenseMap<SDValue, SDValue> Locations;
/// A boolean indicator for each slot listed in the FunctionInfo as to
/// whether it has been used in the current statepoint. Since we try to
/// preserve stack slots across safepoints, there can be gaps in which
/// slots have been allocated.
SmallBitVector AllocatedStackSlots;
/// Points just beyond the last slot known to have been allocated
unsigned NextSlotToAllocate = 0;
/// Keep track of pending gcrelocate calls for consistency check
SmallVector<const GCRelocateInst *, 10> PendingGCRelocateCalls;
} // end namespace llvm