StatepointLowering.cpp | Explore in Territory

//===- StatepointLowering.cpp - SDAGBuilder's statepoint code -------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file includes support code use by SelectionDAGBuilder when lowering a
// statepoint sequence in SelectionDAG IR.
//
//===----------------------------------------------------------------------===//

#include "StatepointLowering.h"
#include "SelectionDAGBuilder.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/GCMetadata.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/RuntimeLibcallUtil.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGenTypes/MachineValueType.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GCStrategy.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Statepoint.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <tuple>
#include <utility>

usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumSlotsAllocatedForStatepoints,
          "Number of stack slots allocated for statepoints");
STATISTIC(NumOfStatepoints, "Number of statepoint nodes encountered");
STATISTIC(StatepointMaxSlotsRequired,
          "Maximum number of stack slots required for a singe statepoint");

static cl::opt<bool> UseRegistersForDeoptValues(
    "use-registers-for-deopt-values", cl::Hidden, cl::init(false),
    cl::desc("Allow using registers for non pointer deopt args"));

static cl::opt<bool> UseRegistersForGCPointersInLandingPad(
    "use-registers-for-gc-values-in-landing-pad", cl::Hidden, cl::init(false),
    cl::desc("Allow using registers for gc pointer in landing pad"));

static cl::opt<unsigned> MaxRegistersForGCPointers(
    "max-registers-for-gc-values", cl::Hidden, cl::init(0),
    cl::desc("Max number of VRegs allowed to pass GC pointer meta args in"));

RecordType;

static void pushStackMapConstant(SmallVectorImpl<SDValue>& Ops,
                                 SelectionDAGBuilder &Builder, uint64_t Value) { … }

void StatepointLoweringState::startNewStatepoint(SelectionDAGBuilder &Builder) { … }

void StatepointLoweringState::clear() { … }

SDValue
StatepointLoweringState::allocateStackSlot(EVT ValueType,
                                           SelectionDAGBuilder &Builder) { … }

/// Utility function for reservePreviousStackSlotForValue. Tries to find
/// stack slot index to which we have spilled value for previous statepoints.
/// LookUpDepth specifies maximum DFS depth this function is allowed to look.
static std::optional<int> findPreviousSpillSlot(const Value *Val,
                                                SelectionDAGBuilder &Builder,
                                                int LookUpDepth) { … }

/// Return true if-and-only-if the given SDValue can be lowered as either a
/// constant argument or a stack reference.  The key point is that the value
/// doesn't need to be spilled or tracked as a vreg use.
static bool willLowerDirectly(SDValue Incoming) { … }

/// Try to find existing copies of the incoming values in stack slots used for
/// statepoint spilling.  If we can find a spill slot for the incoming value,
/// mark that slot as allocated, and reuse the same slot for this safepoint.
/// This helps to avoid series of loads and stores that only serve to reshuffle
/// values on the stack between calls.
static void reservePreviousStackSlotForValue(const Value *IncomingValue,
                                             SelectionDAGBuilder &Builder) { … }

/// Extract call from statepoint, lower it and return pointer to the
/// call node. Also update NodeMap so that getValue(statepoint) will
/// reference lowered call result
static std::pair<SDValue, SDNode *> lowerCallFromStatepointLoweringInfo(
    SelectionDAGBuilder::StatepointLoweringInfo &SI,
    SelectionDAGBuilder &Builder) { … }

static MachineMemOperand* getMachineMemOperand(MachineFunction &MF,
                                               FrameIndexSDNode &FI) { … }

/// Spill a value incoming to the statepoint. It might be either part of
/// vmstate
/// or gcstate. In both cases unconditionally spill it on the stack unless it
/// is a null constant. Return pair with first element being frame index
/// containing saved value and second element with outgoing chain from the
/// emitted store
static std::tuple<SDValue, SDValue, MachineMemOperand*>
spillIncomingStatepointValue(SDValue Incoming, SDValue Chain,
                             SelectionDAGBuilder &Builder) { … }

/// Lower a single value incoming to a statepoint node.  This value can be
/// either a deopt value or a gc value, the handling is the same.  We special
/// case constants and allocas, then fall back to spilling if required.
static void
lowerIncomingStatepointValue(SDValue Incoming, bool RequireSpillSlot,
                             SmallVectorImpl<SDValue> &Ops,
                             SmallVectorImpl<MachineMemOperand *> &MemRefs,
                             SelectionDAGBuilder &Builder) { … }

/// Return true if value V represents the GC value. The behavior is conservative
/// in case it is not sure that value is not GC the function returns true.
static bool isGCValue(const Value *V, SelectionDAGBuilder &Builder) { … }

/// Lower deopt state and gc pointer arguments of the statepoint.  The actual
/// lowering is described in lowerIncomingStatepointValue.  This function is
/// responsible for lowering everything in the right position and playing some
/// tricks to avoid redundant stack manipulation where possible.  On
/// completion, 'Ops' will contain ready to use operands for machine code
/// statepoint. The chain nodes will have already been created and the DAG root
/// will be set to the last value spilled (if any were).
static void
lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,
                        SmallVectorImpl<MachineMemOperand *> &MemRefs,
                        SmallVectorImpl<SDValue> &GCPtrs,
                        DenseMap<SDValue, int> &LowerAsVReg,
                        SelectionDAGBuilder::StatepointLoweringInfo &SI,
                        SelectionDAGBuilder &Builder) { … }

SDValue SelectionDAGBuilder::LowerAsSTATEPOINT(
    SelectionDAGBuilder::StatepointLoweringInfo &SI) { … }

/// Return two gc.results if present.  First result is a block local
/// gc.result, second result is a non-block local gc.result.  Corresponding
/// entry will be nullptr if not present.
static std::pair<const GCResultInst*, const GCResultInst*>
getGCResultLocality(const GCStatepointInst &S) { … }

void
SelectionDAGBuilder::LowerStatepoint(const GCStatepointInst &I,
                                     const BasicBlock *EHPadBB /*= nullptr*/) { … }

void SelectionDAGBuilder::LowerCallSiteWithDeoptBundleImpl(
    const CallBase *Call, SDValue Callee, const BasicBlock *EHPadBB,
    bool VarArgDisallowed, bool ForceVoidReturnTy) { … }

void SelectionDAGBuilder::LowerCallSiteWithDeoptBundle(
    const CallBase *Call, SDValue Callee, const BasicBlock *EHPadBB) { … }

void SelectionDAGBuilder::visitGCResult(const GCResultInst &CI) { … }

void SelectionDAGBuilder::visitGCRelocate(const GCRelocateInst &Relocate) { … }

void SelectionDAGBuilder::LowerDeoptimizeCall(const CallInst *CI) { … }

void SelectionDAGBuilder::LowerDeoptimizingReturn() { … }
llvm/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp
