1327 lines · cpp
1//===- StatepointLowering.cpp - SDAGBuilder's statepoint code -------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file includes support code use by SelectionDAGBuilder when lowering a10// statepoint sequence in SelectionDAG IR.11//12//===----------------------------------------------------------------------===//13 14#include "StatepointLowering.h"15#include "SelectionDAGBuilder.h"16#include "llvm/ADT/ArrayRef.h"17#include "llvm/ADT/STLExtras.h"18#include "llvm/ADT/SetVector.h"19#include "llvm/ADT/SmallBitVector.h"20#include "llvm/ADT/SmallSet.h"21#include "llvm/ADT/SmallVector.h"22#include "llvm/ADT/Statistic.h"23#include "llvm/CodeGen/FunctionLoweringInfo.h"24#include "llvm/CodeGen/GCMetadata.h"25#include "llvm/CodeGen/ISDOpcodes.h"26#include "llvm/CodeGen/MachineFrameInfo.h"27#include "llvm/CodeGen/MachineFunction.h"28#include "llvm/CodeGen/MachineMemOperand.h"29#include "llvm/CodeGen/SelectionDAG.h"30#include "llvm/CodeGen/SelectionDAGNodes.h"31#include "llvm/CodeGen/StackMaps.h"32#include "llvm/CodeGen/TargetLowering.h"33#include "llvm/CodeGen/TargetOpcodes.h"34#include "llvm/CodeGenTypes/MachineValueType.h"35#include "llvm/IR/CallingConv.h"36#include "llvm/IR/DerivedTypes.h"37#include "llvm/IR/GCStrategy.h"38#include "llvm/IR/Instruction.h"39#include "llvm/IR/Instructions.h"40#include "llvm/IR/LLVMContext.h"41#include "llvm/IR/Statepoint.h"42#include "llvm/IR/Type.h"43#include "llvm/Support/Casting.h"44#include "llvm/Support/CommandLine.h"45#include "llvm/Target/TargetMachine.h"46#include "llvm/Target/TargetOptions.h"47#include <cassert>48#include <cstddef>49#include <cstdint>50#include <iterator>51#include <tuple>52#include <utility>53 54using namespace llvm;55 56#define DEBUG_TYPE "statepoint-lowering"57 58STATISTIC(NumSlotsAllocatedForStatepoints,59 "Number of stack slots allocated for statepoints");60STATISTIC(NumOfStatepoints, "Number of statepoint nodes encountered");61STATISTIC(StatepointMaxSlotsRequired,62 "Maximum number of stack slots required for a singe statepoint");63 64static cl::opt<bool> UseRegistersForDeoptValues(65 "use-registers-for-deopt-values", cl::Hidden, cl::init(false),66 cl::desc("Allow using registers for non pointer deopt args"));67 68static cl::opt<bool> UseRegistersForGCPointersInLandingPad(69 "use-registers-for-gc-values-in-landing-pad", cl::Hidden, cl::init(false),70 cl::desc("Allow using registers for gc pointer in landing pad"));71 72static cl::opt<unsigned> MaxRegistersForGCPointers(73 "max-registers-for-gc-values", cl::Hidden, cl::init(0),74 cl::desc("Max number of VRegs allowed to pass GC pointer meta args in"));75 76typedef FunctionLoweringInfo::StatepointRelocationRecord RecordType;77 78static void pushStackMapConstant(SmallVectorImpl<SDValue>& Ops,79 SelectionDAGBuilder &Builder, uint64_t Value) {80 SDLoc L = Builder.getCurSDLoc();81 Ops.push_back(Builder.DAG.getTargetConstant(StackMaps::ConstantOp, L,82 MVT::i64));83 Ops.push_back(Builder.DAG.getTargetConstant(Value, L, MVT::i64));84}85 86void StatepointLoweringState::startNewStatepoint(SelectionDAGBuilder &Builder) {87 // Consistency check88 assert(PendingGCRelocateCalls.empty() &&89 "Trying to visit statepoint before finished processing previous one");90 Locations.clear();91 NextSlotToAllocate = 0;92 // Need to resize this on each safepoint - we need the two to stay in sync and93 // the clear patterns of a SelectionDAGBuilder have no relation to94 // FunctionLoweringInfo. Also need to ensure used bits get cleared.95 AllocatedStackSlots.clear();96 AllocatedStackSlots.resize(Builder.FuncInfo.StatepointStackSlots.size());97}98 99void StatepointLoweringState::clear() {100 Locations.clear();101 AllocatedStackSlots.clear();102 assert(PendingGCRelocateCalls.empty() &&103 "cleared before statepoint sequence completed");104}105 106SDValue107StatepointLoweringState::allocateStackSlot(EVT ValueType,108 SelectionDAGBuilder &Builder) {109 NumSlotsAllocatedForStatepoints++;110 MachineFrameInfo &MFI = Builder.DAG.getMachineFunction().getFrameInfo();111 112 unsigned SpillSize = ValueType.getStoreSize();113 assert((SpillSize * 8) ==114 (-8u & (7 + ValueType.getSizeInBits())) && // Round up modulo 8.115 "Size not in bytes?");116 117 // First look for a previously created stack slot which is not in118 // use (accounting for the fact arbitrary slots may already be119 // reserved), or to create a new stack slot and use it.120 121 const size_t NumSlots = AllocatedStackSlots.size();122 assert(NextSlotToAllocate <= NumSlots && "Broken invariant");123 124 assert(AllocatedStackSlots.size() ==125 Builder.FuncInfo.StatepointStackSlots.size() &&126 "Broken invariant");127 128 for (; NextSlotToAllocate < NumSlots; NextSlotToAllocate++) {129 if (!AllocatedStackSlots.test(NextSlotToAllocate)) {130 const int FI = Builder.FuncInfo.StatepointStackSlots[NextSlotToAllocate];131 if (MFI.getObjectSize(FI) == SpillSize) {132 AllocatedStackSlots.set(NextSlotToAllocate);133 // TODO: Is ValueType the right thing to use here?134 return Builder.DAG.getFrameIndex(FI, ValueType);135 }136 }137 }138 139 // Couldn't find a free slot, so create a new one:140 141 SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType);142 const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();143 MFI.markAsStatepointSpillSlotObjectIndex(FI);144 145 Builder.FuncInfo.StatepointStackSlots.push_back(FI);146 AllocatedStackSlots.resize(AllocatedStackSlots.size()+1, true);147 assert(AllocatedStackSlots.size() ==148 Builder.FuncInfo.StatepointStackSlots.size() &&149 "Broken invariant");150 151 StatepointMaxSlotsRequired.updateMax(152 Builder.FuncInfo.StatepointStackSlots.size());153 154 return SpillSlot;155}156 157/// Utility function for reservePreviousStackSlotForValue. Tries to find158/// stack slot index to which we have spilled value for previous statepoints.159/// LookUpDepth specifies maximum DFS depth this function is allowed to look.160static std::optional<int> findPreviousSpillSlot(const Value *Val,161 SelectionDAGBuilder &Builder,162 int LookUpDepth) {163 // Can not look any further - give up now164 if (LookUpDepth <= 0)165 return std::nullopt;166 167 // Spill location is known for gc relocates168 if (const auto *Relocate = dyn_cast<GCRelocateInst>(Val)) {169 const Value *Statepoint = Relocate->getStatepoint();170 assert((isa<GCStatepointInst>(Statepoint) || isa<UndefValue>(Statepoint)) &&171 "GetStatepoint must return one of two types");172 if (isa<UndefValue>(Statepoint))173 return std::nullopt;174 175 const auto &RelocationMap = Builder.FuncInfo.StatepointRelocationMaps176 [cast<GCStatepointInst>(Statepoint)];177 178 auto It = RelocationMap.find(Relocate);179 if (It == RelocationMap.end())180 return std::nullopt;181 182 auto &Record = It->second;183 if (Record.type != RecordType::Spill)184 return std::nullopt;185 186 return Record.payload.FI;187 }188 189 // Look through bitcast instructions.190 if (const BitCastInst *Cast = dyn_cast<BitCastInst>(Val))191 return findPreviousSpillSlot(Cast->getOperand(0), Builder, LookUpDepth - 1);192 193 // Look through phi nodes194 // All incoming values should have same known stack slot, otherwise result195 // is unknown.196 if (const PHINode *Phi = dyn_cast<PHINode>(Val)) {197 std::optional<int> MergedResult;198 199 for (const auto &IncomingValue : Phi->incoming_values()) {200 std::optional<int> SpillSlot =201 findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth - 1);202 if (!SpillSlot)203 return std::nullopt;204 205 if (MergedResult && *MergedResult != *SpillSlot)206 return std::nullopt;207 208 MergedResult = SpillSlot;209 }210 return MergedResult;211 }212 213 // TODO: We can do better for PHI nodes. In cases like this:214 // ptr = phi(relocated_pointer, not_relocated_pointer)215 // statepoint(ptr)216 // We will return that stack slot for ptr is unknown. And later we might217 // assign different stack slots for ptr and relocated_pointer. This limits218 // llvm's ability to remove redundant stores.219 // Unfortunately it's hard to accomplish in current infrastructure.220 // We use this function to eliminate spill store completely, while221 // in example we still need to emit store, but instead of any location222 // we need to use special "preferred" location.223 224 // TODO: handle simple updates. If a value is modified and the original225 // value is no longer live, it would be nice to put the modified value in the226 // same slot. This allows folding of the memory accesses for some227 // instructions types (like an increment).228 // statepoint (i)229 // i1 = i+1230 // statepoint (i1)231 // However we need to be careful for cases like this:232 // statepoint(i)233 // i1 = i+1234 // statepoint(i, i1)235 // Here we want to reserve spill slot for 'i', but not for 'i+1'. If we just236 // put handling of simple modifications in this function like it's done237 // for bitcasts we might end up reserving i's slot for 'i+1' because order in238 // which we visit values is unspecified.239 240 // Don't know any information about this instruction241 return std::nullopt;242}243 244/// Return true if-and-only-if the given SDValue can be lowered as either a245/// constant argument or a stack reference. The key point is that the value246/// doesn't need to be spilled or tracked as a vreg use.247static bool willLowerDirectly(SDValue Incoming) {248 // We are making an unchecked assumption that the frame size <= 2^16 as that249 // is the largest offset which can be encoded in the stackmap format.250 if (isa<FrameIndexSDNode>(Incoming))251 return true;252 253 // The largest constant describeable in the StackMap format is 64 bits.254 // Potential Optimization: Constants values are sign extended by consumer,255 // and thus there are many constants of static type > 64 bits whose value256 // happens to be sext(Con64) and could thus be lowered directly.257 if (Incoming.getValueType().getSizeInBits() > 64)258 return false;259 260 return isIntOrFPConstant(Incoming) || Incoming.isUndef();261}262 263/// Try to find existing copies of the incoming values in stack slots used for264/// statepoint spilling. If we can find a spill slot for the incoming value,265/// mark that slot as allocated, and reuse the same slot for this safepoint.266/// This helps to avoid series of loads and stores that only serve to reshuffle267/// values on the stack between calls.268static void reservePreviousStackSlotForValue(const Value *IncomingValue,269 SelectionDAGBuilder &Builder) {270 SDValue Incoming = Builder.getValue(IncomingValue);271 272 // If we won't spill this, we don't need to check for previously allocated273 // stack slots.274 if (willLowerDirectly(Incoming))275 return;276 277 SDValue OldLocation = Builder.StatepointLowering.getLocation(Incoming);278 if (OldLocation.getNode())279 // Duplicates in input280 return;281 282 const int LookUpDepth = 6;283 std::optional<int> Index =284 findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth);285 if (!Index)286 return;287 288 const auto &StatepointSlots = Builder.FuncInfo.StatepointStackSlots;289 290 auto SlotIt = find(StatepointSlots, *Index);291 assert(SlotIt != StatepointSlots.end() &&292 "Value spilled to the unknown stack slot");293 294 // This is one of our dedicated lowering slots295 const int Offset = std::distance(StatepointSlots.begin(), SlotIt);296 if (Builder.StatepointLowering.isStackSlotAllocated(Offset)) {297 // stack slot already assigned to someone else, can't use it!298 // TODO: currently we reserve space for gc arguments after doing299 // normal allocation for deopt arguments. We should reserve for300 // _all_ deopt and gc arguments, then start allocating. This301 // will prevent some moves being inserted when vm state changes,302 // but gc state doesn't between two calls.303 return;304 }305 // Reserve this stack slot306 Builder.StatepointLowering.reserveStackSlot(Offset);307 308 // Cache this slot so we find it when going through the normal309 // assignment loop.310 SDValue Loc =311 Builder.DAG.getTargetFrameIndex(*Index, Builder.getFrameIndexTy());312 Builder.StatepointLowering.setLocation(Incoming, Loc);313}314 315/// Extract call from statepoint, lower it and return pointer to the316/// call node. Also update NodeMap so that getValue(statepoint) will317/// reference lowered call result318static std::pair<SDValue, SDNode *> lowerCallFromStatepointLoweringInfo(319 SelectionDAGBuilder::StatepointLoweringInfo &SI,320 SelectionDAGBuilder &Builder) {321 SDValue ReturnValue, CallEndVal;322 std::tie(ReturnValue, CallEndVal) =323 Builder.lowerInvokable(SI.CLI, SI.EHPadBB);324 SDNode *CallEnd = CallEndVal.getNode();325 326 // Get a call instruction from the call sequence chain. Tail calls are not327 // allowed. The following code is essentially reverse engineering X86's328 // LowerCallTo.329 //330 // We are expecting DAG to have the following form:331 //332 // ch = eh_label (only in case of invoke statepoint)333 // ch, glue = callseq_start ch334 // ch, glue = X86::Call ch, glue335 // ch, glue = callseq_end ch, glue336 // get_return_value ch, glue337 //338 // get_return_value can either be a sequence of CopyFromReg instructions339 // to grab the return value from the return register(s), or it can be a LOAD340 // to load a value returned by reference via a stack slot.341 342 if (CallEnd->getOpcode() == ISD::EH_LABEL)343 CallEnd = CallEnd->getOperand(0).getNode();344 345 bool HasDef = !SI.CLI.RetTy->isVoidTy();346 if (HasDef) {347 if (CallEnd->getOpcode() == ISD::LOAD)348 CallEnd = CallEnd->getOperand(0).getNode();349 else350 while (CallEnd->getOpcode() == ISD::CopyFromReg)351 CallEnd = CallEnd->getOperand(0).getNode();352 }353 354 assert(CallEnd->getOpcode() == ISD::CALLSEQ_END && "expected!");355 return std::make_pair(ReturnValue, CallEnd->getOperand(0).getNode());356}357 358static MachineMemOperand* getMachineMemOperand(MachineFunction &MF,359 FrameIndexSDNode &FI) {360 auto PtrInfo = MachinePointerInfo::getFixedStack(MF, FI.getIndex());361 auto MMOFlags = MachineMemOperand::MOStore |362 MachineMemOperand::MOLoad | MachineMemOperand::MOVolatile;363 auto &MFI = MF.getFrameInfo();364 return MF.getMachineMemOperand(PtrInfo, MMOFlags,365 MFI.getObjectSize(FI.getIndex()),366 MFI.getObjectAlign(FI.getIndex()));367}368 369/// Spill a value incoming to the statepoint. It might be either part of370/// vmstate371/// or gcstate. In both cases unconditionally spill it on the stack unless it372/// is a null constant. Return pair with first element being frame index373/// containing saved value and second element with outgoing chain from the374/// emitted store375static std::tuple<SDValue, SDValue, MachineMemOperand*>376spillIncomingStatepointValue(SDValue Incoming, SDValue Chain,377 SelectionDAGBuilder &Builder) {378 SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);379 MachineMemOperand* MMO = nullptr;380 381 // Emit new store if we didn't do it for this ptr before382 if (!Loc.getNode()) {383 Loc = Builder.StatepointLowering.allocateStackSlot(Incoming.getValueType(),384 Builder);385 int Index = cast<FrameIndexSDNode>(Loc)->getIndex();386 // We use TargetFrameIndex so that isel will not select it into LEA387 Loc = Builder.DAG.getTargetFrameIndex(Index, Builder.getFrameIndexTy());388 389 // Right now we always allocate spill slots that are of the same390 // size as the value we're about to spill (the size of spillee can391 // vary since we spill vectors of pointers too). At some point we392 // can consider allowing spills of smaller values to larger slots393 // (i.e. change the '==' in the assert below to a '>=').394 MachineFrameInfo &MFI = Builder.DAG.getMachineFunction().getFrameInfo();395 assert((MFI.getObjectSize(Index) * 8) ==396 (-8 & (7 + // Round up modulo 8.397 (int64_t)Incoming.getValueSizeInBits())) &&398 "Bad spill: stack slot does not match!");399 400 // Note: Using the alignment of the spill slot (rather than the abi or401 // preferred alignment) is required for correctness when dealing with spill402 // slots with preferred alignments larger than frame alignment..403 auto &MF = Builder.DAG.getMachineFunction();404 auto PtrInfo = MachinePointerInfo::getFixedStack(MF, Index);405 auto *StoreMMO = MF.getMachineMemOperand(406 PtrInfo, MachineMemOperand::MOStore, MFI.getObjectSize(Index),407 MFI.getObjectAlign(Index));408 Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc,409 StoreMMO);410 411 MMO = getMachineMemOperand(MF, *cast<FrameIndexSDNode>(Loc));412 413 Builder.StatepointLowering.setLocation(Incoming, Loc);414 }415 416 assert(Loc.getNode());417 return std::make_tuple(Loc, Chain, MMO);418}419 420/// Lower a single value incoming to a statepoint node. This value can be421/// either a deopt value or a gc value, the handling is the same. We special422/// case constants and allocas, then fall back to spilling if required.423static void424lowerIncomingStatepointValue(SDValue Incoming, bool RequireSpillSlot,425 SmallVectorImpl<SDValue> &Ops,426 SmallVectorImpl<MachineMemOperand *> &MemRefs,427 SelectionDAGBuilder &Builder) {428 429 if (willLowerDirectly(Incoming)) {430 if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) {431 // This handles allocas as arguments to the statepoint (this is only432 // really meaningful for a deopt value. For GC, we'd be trying to433 // relocate the address of the alloca itself?)434 assert(Incoming.getValueType() == Builder.getFrameIndexTy() &&435 "Incoming value is a frame index!");436 Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(),437 Builder.getFrameIndexTy()));438 439 auto &MF = Builder.DAG.getMachineFunction();440 auto *MMO = getMachineMemOperand(MF, *FI);441 MemRefs.push_back(MMO);442 return;443 }444 445 assert(Incoming.getValueType().getSizeInBits() <= 64);446 447 if (Incoming.isUndef()) {448 // Put an easily recognized constant that's unlikely to be a valid449 // value so that uses of undef by the consumer of the stackmap is450 // easily recognized. This is legal since the compiler is always451 // allowed to chose an arbitrary value for undef.452 pushStackMapConstant(Ops, Builder, 0xFEFEFEFE);453 return;454 }455 456 // If the original value was a constant, make sure it gets recorded as457 // such in the stackmap. This is required so that the consumer can458 // parse any internal format to the deopt state. It also handles null459 // pointers and other constant pointers in GC states.460 if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) {461 pushStackMapConstant(Ops, Builder, C->getSExtValue());462 return;463 } else if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Incoming)) {464 pushStackMapConstant(Ops, Builder,465 C->getValueAPF().bitcastToAPInt().getZExtValue());466 return;467 }468 469 llvm_unreachable("unhandled direct lowering case");470 }471 472 473 474 if (!RequireSpillSlot) {475 // If this value is live in (not live-on-return, or live-through), we can476 // treat it the same way patchpoint treats it's "live in" values. We'll477 // end up folding some of these into stack references, but they'll be478 // handled by the register allocator. Note that we do not have the notion479 // of a late use so these values might be placed in registers which are480 // clobbered by the call. This is fine for live-in. For live-through481 // fix-up pass should be executed to force spilling of such registers.482 Ops.push_back(Incoming);483 } else {484 // Otherwise, locate a spill slot and explicitly spill it so it can be485 // found by the runtime later. Note: We know all of these spills are486 // independent, but don't bother to exploit that chain wise. DAGCombine487 // will happily do so as needed, so doing it here would be a small compile488 // time win at most. 489 SDValue Chain = Builder.getRoot();490 auto Res = spillIncomingStatepointValue(Incoming, Chain, Builder);491 Ops.push_back(std::get<0>(Res));492 if (auto *MMO = std::get<2>(Res))493 MemRefs.push_back(MMO);494 Chain = std::get<1>(Res);495 Builder.DAG.setRoot(Chain);496 }497 498}499 500/// Return true if value V represents the GC value. The behavior is conservative501/// in case it is not sure that value is not GC the function returns true.502static bool isGCValue(const Value *V, SelectionDAGBuilder &Builder) {503 auto *Ty = V->getType();504 if (!Ty->isPtrOrPtrVectorTy())505 return false;506 if (auto *GFI = Builder.GFI)507 if (auto IsManaged = GFI->getStrategy().isGCManagedPointer(Ty))508 return *IsManaged;509 return true; // conservative510}511 512/// Lower deopt state and gc pointer arguments of the statepoint. The actual513/// lowering is described in lowerIncomingStatepointValue. This function is514/// responsible for lowering everything in the right position and playing some515/// tricks to avoid redundant stack manipulation where possible. On516/// completion, 'Ops' will contain ready to use operands for machine code517/// statepoint. The chain nodes will have already been created and the DAG root518/// will be set to the last value spilled (if any were).519static void520lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,521 SmallVectorImpl<MachineMemOperand *> &MemRefs,522 SmallVectorImpl<SDValue> &GCPtrs,523 DenseMap<SDValue, int> &LowerAsVReg,524 SelectionDAGBuilder::StatepointLoweringInfo &SI,525 SelectionDAGBuilder &Builder) {526 // Lower the deopt and gc arguments for this statepoint. Layout will be:527 // deopt argument length, deopt arguments.., gc arguments...528 529 // Figure out what lowering strategy we're going to use for each part530 // Note: It is conservatively correct to lower both "live-in" and "live-out"531 // as "live-through". A "live-through" variable is one which is "live-in",532 // "live-out", and live throughout the lifetime of the call (i.e. we can find533 // it from any PC within the transitive callee of the statepoint). In534 // particular, if the callee spills callee preserved registers we may not535 // be able to find a value placed in that register during the call. This is536 // fine for live-out, but not for live-through. If we were willing to make537 // assumptions about the code generator producing the callee, we could538 // potentially allow live-through values in callee saved registers.539 const bool LiveInDeopt =540 SI.StatepointFlags & (uint64_t)StatepointFlags::DeoptLiveIn;541 542 // Decide which deriver pointers will go on VRegs543 unsigned MaxVRegPtrs = MaxRegistersForGCPointers.getValue();544 545 // Pointers used on exceptional path of invoke statepoint.546 // We cannot assing them to VRegs.547 SmallSet<SDValue, 8> LPadPointers;548 if (!UseRegistersForGCPointersInLandingPad)549 if (const auto *StInvoke =550 dyn_cast_or_null<InvokeInst>(SI.StatepointInstr)) {551 LandingPadInst *LPI = StInvoke->getLandingPadInst();552 for (const auto *Relocate : SI.GCRelocates)553 if (Relocate->getOperand(0) == LPI) {554 LPadPointers.insert(Builder.getValue(Relocate->getBasePtr()));555 LPadPointers.insert(Builder.getValue(Relocate->getDerivedPtr()));556 }557 }558 559 LLVM_DEBUG(dbgs() << "Deciding how to lower GC Pointers:\n");560 561 // List of unique lowered GC Pointer values.562 SmallSetVector<SDValue, 16> LoweredGCPtrs;563 // Map lowered GC Pointer value to the index in above vector564 DenseMap<SDValue, unsigned> GCPtrIndexMap;565 566 unsigned CurNumVRegs = 0;567 568 auto canPassGCPtrOnVReg = [&](SDValue SD) {569 if (SD.getValueType().isVector())570 return false;571 if (LPadPointers.count(SD))572 return false;573 return !willLowerDirectly(SD);574 };575 576 auto processGCPtr = [&](const Value *V) {577 SDValue PtrSD = Builder.getValue(V);578 if (!LoweredGCPtrs.insert(PtrSD))579 return; // skip duplicates580 GCPtrIndexMap[PtrSD] = LoweredGCPtrs.size() - 1;581 582 assert(!LowerAsVReg.count(PtrSD) && "must not have been seen");583 if (LowerAsVReg.size() == MaxVRegPtrs)584 return;585 assert(V->getType()->isVectorTy() == PtrSD.getValueType().isVector() &&586 "IR and SD types disagree");587 if (!canPassGCPtrOnVReg(PtrSD)) {588 LLVM_DEBUG(dbgs() << "direct/spill "; PtrSD.dump(&Builder.DAG));589 return;590 }591 LLVM_DEBUG(dbgs() << "vreg "; PtrSD.dump(&Builder.DAG));592 LowerAsVReg[PtrSD] = CurNumVRegs++;593 };594 595 // Process derived pointers first to give them more chance to go on VReg.596 for (const Value *V : SI.Ptrs)597 processGCPtr(V);598 for (const Value *V : SI.Bases)599 processGCPtr(V);600 601 LLVM_DEBUG(dbgs() << LowerAsVReg.size() << " pointers will go in vregs\n");602 603 auto requireSpillSlot = [&](const Value *V) {604 if (!Builder.DAG.getTargetLoweringInfo().isTypeLegal(605 Builder.getValue(V).getValueType()))606 return true;607 if (isGCValue(V, Builder))608 return !LowerAsVReg.count(Builder.getValue(V));609 return !(LiveInDeopt || UseRegistersForDeoptValues);610 };611 612 // Before we actually start lowering (and allocating spill slots for values),613 // reserve any stack slots which we judge to be profitable to reuse for a614 // particular value. This is purely an optimization over the code below and615 // doesn't change semantics at all. It is important for performance that we616 // reserve slots for both deopt and gc values before lowering either.617 for (const Value *V : SI.DeoptState) {618 if (requireSpillSlot(V))619 reservePreviousStackSlotForValue(V, Builder);620 }621 622 for (const Value *V : SI.Ptrs) {623 SDValue SDV = Builder.getValue(V);624 if (!LowerAsVReg.count(SDV))625 reservePreviousStackSlotForValue(V, Builder);626 }627 628 for (const Value *V : SI.Bases) {629 SDValue SDV = Builder.getValue(V);630 if (!LowerAsVReg.count(SDV))631 reservePreviousStackSlotForValue(V, Builder);632 }633 634 // First, prefix the list with the number of unique values to be635 // lowered. Note that this is the number of *Values* not the636 // number of SDValues required to lower them.637 const int NumVMSArgs = SI.DeoptState.size();638 pushStackMapConstant(Ops, Builder, NumVMSArgs);639 640 // The vm state arguments are lowered in an opaque manner. We do not know641 // what type of values are contained within.642 LLVM_DEBUG(dbgs() << "Lowering deopt state\n");643 for (const Value *V : SI.DeoptState) {644 SDValue Incoming;645 // If this is a function argument at a static frame index, generate it as646 // the frame index.647 if (const Argument *Arg = dyn_cast<Argument>(V)) {648 int FI = Builder.FuncInfo.getArgumentFrameIndex(Arg);649 if (FI != INT_MAX)650 Incoming = Builder.DAG.getFrameIndex(FI, Builder.getFrameIndexTy());651 }652 if (!Incoming.getNode())653 Incoming = Builder.getValue(V);654 LLVM_DEBUG(dbgs() << "Value " << *V655 << " requireSpillSlot = " << requireSpillSlot(V) << "\n");656 lowerIncomingStatepointValue(Incoming, requireSpillSlot(V), Ops, MemRefs,657 Builder);658 }659 660 // Finally, go ahead and lower all the gc arguments.661 pushStackMapConstant(Ops, Builder, LoweredGCPtrs.size());662 for (SDValue SDV : LoweredGCPtrs)663 lowerIncomingStatepointValue(SDV, !LowerAsVReg.count(SDV), Ops, MemRefs,664 Builder);665 666 // Copy to out vector. LoweredGCPtrs will be empty after this point.667 GCPtrs = LoweredGCPtrs.takeVector();668 669 // If there are any explicit spill slots passed to the statepoint, record670 // them, but otherwise do not do anything special. These are user provided671 // allocas and give control over placement to the consumer. In this case,672 // it is the contents of the slot which may get updated, not the pointer to673 // the alloca674 SmallVector<SDValue, 4> Allocas;675 for (Value *V : SI.GCLives) {676 SDValue Incoming = Builder.getValue(V);677 if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) {678 // This handles allocas as arguments to the statepoint679 assert(Incoming.getValueType() == Builder.getFrameIndexTy() &&680 "Incoming value is a frame index!");681 Allocas.push_back(Builder.DAG.getTargetFrameIndex(682 FI->getIndex(), Builder.getFrameIndexTy()));683 684 auto &MF = Builder.DAG.getMachineFunction();685 auto *MMO = getMachineMemOperand(MF, *FI);686 MemRefs.push_back(MMO);687 }688 }689 pushStackMapConstant(Ops, Builder, Allocas.size());690 Ops.append(Allocas.begin(), Allocas.end());691 692 // Now construct GC base/derived map;693 pushStackMapConstant(Ops, Builder, SI.Ptrs.size());694 SDLoc L = Builder.getCurSDLoc();695 for (unsigned i = 0; i < SI.Ptrs.size(); ++i) {696 SDValue Base = Builder.getValue(SI.Bases[i]);697 assert(GCPtrIndexMap.count(Base) && "base not found in index map");698 Ops.push_back(699 Builder.DAG.getTargetConstant(GCPtrIndexMap[Base], L, MVT::i64));700 SDValue Derived = Builder.getValue(SI.Ptrs[i]);701 assert(GCPtrIndexMap.count(Derived) && "derived not found in index map");702 Ops.push_back(703 Builder.DAG.getTargetConstant(GCPtrIndexMap[Derived], L, MVT::i64));704 }705}706 707SDValue SelectionDAGBuilder::LowerAsSTATEPOINT(708 SelectionDAGBuilder::StatepointLoweringInfo &SI) {709 // The basic scheme here is that information about both the original call and710 // the safepoint is encoded in the CallInst. We create a temporary call and711 // lower it, then reverse engineer the calling sequence.712 713 NumOfStatepoints++;714 // Clear state715 StatepointLowering.startNewStatepoint(*this);716 assert(SI.Bases.size() == SI.Ptrs.size() && "Pointer without base!");717 assert((GFI || SI.Bases.empty()) &&718 "No gc specified, so cannot relocate pointers!");719 720 LLVM_DEBUG(if (SI.StatepointInstr) dbgs()721 << "Lowering statepoint " << *SI.StatepointInstr << "\n");722#ifndef NDEBUG723 for (const auto *Reloc : SI.GCRelocates)724 if (Reloc->getParent() == SI.StatepointInstr->getParent())725 StatepointLowering.scheduleRelocCall(*Reloc);726#endif727 728 // Lower statepoint vmstate and gcstate arguments729 730 // All lowered meta args.731 SmallVector<SDValue, 10> LoweredMetaArgs;732 // Lowered GC pointers (subset of above).733 SmallVector<SDValue, 16> LoweredGCArgs;734 SmallVector<MachineMemOperand*, 16> MemRefs;735 // Maps derived pointer SDValue to statepoint result of relocated pointer.736 DenseMap<SDValue, int> LowerAsVReg;737 lowerStatepointMetaArgs(LoweredMetaArgs, MemRefs, LoweredGCArgs, LowerAsVReg,738 SI, *this);739 740 // Now that we've emitted the spills, we need to update the root so that the741 // call sequence is ordered correctly.742 SI.CLI.setChain(getRoot());743 744 // Get call node, we will replace it later with statepoint745 SDValue ReturnVal;746 SDNode *CallNode;747 std::tie(ReturnVal, CallNode) = lowerCallFromStatepointLoweringInfo(SI, *this);748 749 // Construct the actual GC_TRANSITION_START, STATEPOINT, and GC_TRANSITION_END750 // nodes with all the appropriate arguments and return values.751 752 // Call Node: Chain, Target, {Args}, RegMask, [Glue]753 SDValue Chain = CallNode->getOperand(0);754 755 SDValue Glue;756 bool CallHasIncomingGlue = CallNode->getGluedNode();757 if (CallHasIncomingGlue) {758 // Glue is always last operand759 Glue = CallNode->getOperand(CallNode->getNumOperands() - 1);760 }761 762 // Build the GC_TRANSITION_START node if necessary.763 //764 // The operands to the GC_TRANSITION_{START,END} nodes are laid out in the765 // order in which they appear in the call to the statepoint intrinsic. If766 // any of the operands is a pointer-typed, that operand is immediately767 // followed by a SRCVALUE for the pointer that may be used during lowering768 // (e.g. to form MachinePointerInfo values for loads/stores).769 const bool IsGCTransition =770 (SI.StatepointFlags & (uint64_t)StatepointFlags::GCTransition) ==771 (uint64_t)StatepointFlags::GCTransition;772 if (IsGCTransition) {773 SmallVector<SDValue, 8> TSOps;774 775 // Add chain776 TSOps.push_back(Chain);777 778 // Add GC transition arguments779 for (const Value *V : SI.GCTransitionArgs) {780 TSOps.push_back(getValue(V));781 if (V->getType()->isPointerTy())782 TSOps.push_back(DAG.getSrcValue(V));783 }784 785 // Add glue if necessary786 if (CallHasIncomingGlue)787 TSOps.push_back(Glue);788 789 SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);790 791 SDValue GCTransitionStart =792 DAG.getNode(ISD::GC_TRANSITION_START, getCurSDLoc(), NodeTys, TSOps);793 794 Chain = GCTransitionStart.getValue(0);795 Glue = GCTransitionStart.getValue(1);796 }797 798 // TODO: Currently, all of these operands are being marked as read/write in799 // PrologEpilougeInserter.cpp, we should special case the VMState arguments800 // and flags to be read-only.801 SmallVector<SDValue, 40> Ops;802 803 // Add the <id> and <numBytes> constants.804 Ops.push_back(DAG.getTargetConstant(SI.ID, getCurSDLoc(), MVT::i64));805 Ops.push_back(806 DAG.getTargetConstant(SI.NumPatchBytes, getCurSDLoc(), MVT::i32));807 808 // Calculate and push starting position of vmstate arguments809 // Get number of arguments incoming directly into call node810 unsigned NumCallRegArgs =811 CallNode->getNumOperands() - (CallHasIncomingGlue ? 4 : 3);812 Ops.push_back(DAG.getTargetConstant(NumCallRegArgs, getCurSDLoc(), MVT::i32));813 814 // Add call target815 SDValue CallTarget = SDValue(CallNode->getOperand(1).getNode(), 0);816 Ops.push_back(CallTarget);817 818 // Add call arguments819 // Get position of register mask in the call820 SDNode::op_iterator RegMaskIt;821 if (CallHasIncomingGlue)822 RegMaskIt = CallNode->op_end() - 2;823 else824 RegMaskIt = CallNode->op_end() - 1;825 Ops.insert(Ops.end(), CallNode->op_begin() + 2, RegMaskIt);826 827 // Add a constant argument for the calling convention828 pushStackMapConstant(Ops, *this, SI.CLI.CallConv);829 830 // Add a constant argument for the flags831 uint64_t Flags = SI.StatepointFlags;832 assert(((Flags & ~(uint64_t)StatepointFlags::MaskAll) == 0) &&833 "Unknown flag used");834 pushStackMapConstant(Ops, *this, Flags);835 836 // Insert all vmstate and gcstate arguments837 llvm::append_range(Ops, LoweredMetaArgs);838 839 // Add register mask from call node840 Ops.push_back(*RegMaskIt);841 842 // Add chain843 Ops.push_back(Chain);844 845 // Same for the glue, but we add it only if original call had it846 if (Glue.getNode())847 Ops.push_back(Glue);848 849 // Compute return values. Provide a glue output since we consume one as850 // input. This allows someone else to chain off us as needed.851 SmallVector<EVT, 8> NodeTys;852 for (auto SD : LoweredGCArgs) {853 if (!LowerAsVReg.count(SD))854 continue;855 NodeTys.push_back(SD.getValueType());856 }857 LLVM_DEBUG(dbgs() << "Statepoint has " << NodeTys.size() << " results\n");858 assert(NodeTys.size() == LowerAsVReg.size() && "Inconsistent GC Ptr lowering");859 NodeTys.push_back(MVT::Other);860 NodeTys.push_back(MVT::Glue);861 862 unsigned NumResults = NodeTys.size();863 MachineSDNode *StatepointMCNode =864 DAG.getMachineNode(TargetOpcode::STATEPOINT, getCurSDLoc(), NodeTys, Ops);865 DAG.setNodeMemRefs(StatepointMCNode, MemRefs);866 867 // For values lowered to tied-defs, create the virtual registers if used868 // in other blocks. For local gc.relocate record appropriate statepoint869 // result in StatepointLoweringState.870 DenseMap<SDValue, Register> VirtRegs;871 for (const auto *Relocate : SI.GCRelocates) {872 Value *Derived = Relocate->getDerivedPtr();873 SDValue SD = getValue(Derived);874 auto It = LowerAsVReg.find(SD);875 if (It == LowerAsVReg.end())876 continue;877 878 SDValue Relocated = SDValue(StatepointMCNode, It->second);879 880 // Handle local relocate. Note that different relocates might881 // map to the same SDValue.882 if (SI.StatepointInstr->getParent() == Relocate->getParent()) {883 SDValue Res = StatepointLowering.getLocation(SD);884 if (Res)885 assert(Res == Relocated);886 else887 StatepointLowering.setLocation(SD, Relocated);888 continue;889 }890 891 // Handle multiple gc.relocates of the same input efficiently.892 auto [VRegIt, Inserted] = VirtRegs.try_emplace(SD);893 if (!Inserted)894 continue;895 896 auto *RetTy = Relocate->getType();897 Register Reg = FuncInfo.CreateRegs(RetTy);898 RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(),899 DAG.getDataLayout(), Reg, RetTy, std::nullopt);900 SDValue Chain = DAG.getRoot();901 RFV.getCopyToRegs(Relocated, DAG, getCurSDLoc(), Chain, nullptr);902 PendingExports.push_back(Chain);903 904 VRegIt->second = Reg;905 }906 907 // Record for later use how each relocation was lowered. This is needed to908 // allow later gc.relocates to mirror the lowering chosen.909 const Instruction *StatepointInstr = SI.StatepointInstr;910 auto &RelocationMap = FuncInfo.StatepointRelocationMaps[StatepointInstr];911 for (const GCRelocateInst *Relocate : SI.GCRelocates) {912 const Value *V = Relocate->getDerivedPtr();913 SDValue SDV = getValue(V);914 SDValue Loc = StatepointLowering.getLocation(SDV);915 916 bool IsLocal = (Relocate->getParent() == StatepointInstr->getParent());917 918 RecordType Record;919 if (LowerAsVReg.count(SDV)) {920 if (IsLocal) {921 // Result is already stored in StatepointLowering922 Record.type = RecordType::SDValueNode;923 } else {924 Record.type = RecordType::VReg;925 auto It = VirtRegs.find(SDV);926 assert(It != VirtRegs.end());927 Record.payload.Reg = It->second;928 }929 } else if (Loc.getNode()) {930 Record.type = RecordType::Spill;931 Record.payload.FI = cast<FrameIndexSDNode>(Loc)->getIndex();932 } else {933 Record.type = RecordType::NoRelocate;934 // If we didn't relocate a value, we'll essentialy end up inserting an935 // additional use of the original value when lowering the gc.relocate.936 // We need to make sure the value is available at the new use, which937 // might be in another block.938 if (Relocate->getParent() != StatepointInstr->getParent())939 ExportFromCurrentBlock(V);940 }941 RelocationMap[Relocate] = Record;942 }943 944 945 946 SDNode *SinkNode = StatepointMCNode;947 948 // Build the GC_TRANSITION_END node if necessary.949 //950 // See the comment above regarding GC_TRANSITION_START for the layout of951 // the operands to the GC_TRANSITION_END node.952 if (IsGCTransition) {953 SmallVector<SDValue, 8> TEOps;954 955 // Add chain956 TEOps.push_back(SDValue(StatepointMCNode, NumResults - 2));957 958 // Add GC transition arguments959 for (const Value *V : SI.GCTransitionArgs) {960 TEOps.push_back(getValue(V));961 if (V->getType()->isPointerTy())962 TEOps.push_back(DAG.getSrcValue(V));963 }964 965 // Add glue966 TEOps.push_back(SDValue(StatepointMCNode, NumResults - 1));967 968 SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);969 970 SDValue GCTransitionStart =971 DAG.getNode(ISD::GC_TRANSITION_END, getCurSDLoc(), NodeTys, TEOps);972 973 SinkNode = GCTransitionStart.getNode();974 }975 976 // Replace original call977 // Call: ch,glue = CALL ...978 // Statepoint: [gc relocates],ch,glue = STATEPOINT ...979 unsigned NumSinkValues = SinkNode->getNumValues();980 SDValue StatepointValues[2] = {SDValue(SinkNode, NumSinkValues - 2),981 SDValue(SinkNode, NumSinkValues - 1)};982 DAG.ReplaceAllUsesWith(CallNode, StatepointValues);983 // Remove original call node984 DAG.DeleteNode(CallNode);985 986 // Since we always emit CopyToRegs (even for local relocates), we must987 // update root, so that they are emitted before any local uses.988 (void)getControlRoot();989 990 // TODO: A better future implementation would be to emit a single variable991 // argument, variable return value STATEPOINT node here and then hookup the992 // return value of each gc.relocate to the respective output of the993 // previously emitted STATEPOINT value. Unfortunately, this doesn't appear994 // to actually be possible today.995 996 return ReturnVal;997}998 999/// Return two gc.results if present. First result is a block local1000/// gc.result, second result is a non-block local gc.result. Corresponding1001/// entry will be nullptr if not present.1002static std::pair<const GCResultInst*, const GCResultInst*>1003getGCResultLocality(const GCStatepointInst &S) {1004 std::pair<const GCResultInst *, const GCResultInst*> Res(nullptr, nullptr);1005 for (const auto *U : S.users()) {1006 auto *GRI = dyn_cast<GCResultInst>(U);1007 if (!GRI)1008 continue;1009 if (GRI->getParent() == S.getParent())1010 Res.first = GRI;1011 else1012 Res.second = GRI;1013 }1014 return Res;1015}1016 1017void1018SelectionDAGBuilder::LowerStatepoint(const GCStatepointInst &I,1019 const BasicBlock *EHPadBB /*= nullptr*/) {1020 assert(I.getCallingConv() != CallingConv::AnyReg &&1021 "anyregcc is not supported on statepoints!");1022 1023#ifndef NDEBUG1024 // Check that the associated GCStrategy expects to encounter statepoints.1025 assert(GFI->getStrategy().useStatepoints() &&1026 "GCStrategy does not expect to encounter statepoints");1027#endif1028 1029 SDValue ActualCallee;1030 SDValue Callee = getValue(I.getActualCalledOperand());1031 1032 if (I.getNumPatchBytes() > 0) {1033 // If we've been asked to emit a nop sequence instead of a call instruction1034 // for this statepoint then don't lower the call target, but use a constant1035 // `undef` instead. Not lowering the call target lets statepoint clients1036 // get away without providing a physical address for the symbolic call1037 // target at link time.1038 ActualCallee = DAG.getUNDEF(Callee.getValueType());1039 } else {1040 ActualCallee = Callee;1041 }1042 1043 const auto GCResultLocality = getGCResultLocality(I);1044 AttributeSet retAttrs;1045 if (GCResultLocality.first)1046 retAttrs = GCResultLocality.first->getAttributes().getRetAttrs();1047 1048 StatepointLoweringInfo SI(DAG);1049 populateCallLoweringInfo(SI.CLI, &I, GCStatepointInst::CallArgsBeginPos,1050 I.getNumCallArgs(), ActualCallee,1051 I.getActualReturnType(), retAttrs,1052 /*IsPatchPoint=*/false);1053 1054 // There may be duplication in the gc.relocate list; such as two copies of1055 // each relocation on normal and exceptional path for an invoke. We only1056 // need to spill once and record one copy in the stackmap, but we need to1057 // reload once per gc.relocate. (Dedupping gc.relocates is trickier and best1058 // handled as a CSE problem elsewhere.)1059 // TODO: There a couple of major stackmap size optimizations we could do1060 // here if we wished.1061 // 1) If we've encountered a derived pair {B, D}, we don't need to actually1062 // record {B,B} if it's seen later.1063 // 2) Due to rematerialization, actual derived pointers are somewhat rare;1064 // given that, we could change the format to record base pointer relocations1065 // separately with half the space. This would require a format rev and a1066 // fairly major rework of the STATEPOINT node though.1067 SmallSet<SDValue, 8> Seen;1068 for (const GCRelocateInst *Relocate : I.getGCRelocates()) {1069 SI.GCRelocates.push_back(Relocate);1070 1071 SDValue DerivedSD = getValue(Relocate->getDerivedPtr());1072 if (Seen.insert(DerivedSD).second) {1073 SI.Bases.push_back(Relocate->getBasePtr());1074 SI.Ptrs.push_back(Relocate->getDerivedPtr());1075 }1076 }1077 1078 // If we find a deopt value which isn't explicitly added, we need to1079 // ensure it gets lowered such that gc cycles occurring before the1080 // deoptimization event during the lifetime of the call don't invalidate1081 // the pointer we're deopting with. Note that we assume that all1082 // pointers passed to deopt are base pointers; relaxing that assumption1083 // would require relatively large changes to how we represent relocations.1084 for (Value *V : I.deopt_operands()) {1085 if (!isGCValue(V, *this))1086 continue;1087 if (Seen.insert(getValue(V)).second) {1088 SI.Bases.push_back(V);1089 SI.Ptrs.push_back(V);1090 }1091 }1092 1093 SI.GCLives = ArrayRef<const Use>(I.gc_live_begin(), I.gc_live_end());1094 SI.StatepointInstr = &I;1095 SI.ID = I.getID();1096 1097 SI.DeoptState = ArrayRef<const Use>(I.deopt_begin(), I.deopt_end());1098 SI.GCTransitionArgs = ArrayRef<const Use>(I.gc_transition_args_begin(),1099 I.gc_transition_args_end());1100 1101 SI.StatepointFlags = I.getFlags();1102 SI.NumPatchBytes = I.getNumPatchBytes();1103 SI.EHPadBB = EHPadBB;1104 1105 SDValue ReturnValue = LowerAsSTATEPOINT(SI);1106 1107 // Export the result value if needed1108 if (!GCResultLocality.first && !GCResultLocality.second) {1109 // The return value is not needed, just generate a poison value.1110 // Note: This covers the void return case.1111 setValue(&I, DAG.getIntPtrConstant(-1, getCurSDLoc()));1112 return;1113 }1114 1115 if (GCResultLocality.first) {1116 // Result value will be used in a same basic block. Don't export it or1117 // perform any explicit register copies. The gc_result will simply grab1118 // this value. 1119 setValue(&I, ReturnValue);1120 }1121 1122 if (!GCResultLocality.second)1123 return;1124 // Result value will be used in a different basic block so we need to export1125 // it now. Default exporting mechanism will not work here because statepoint1126 // call has a different type than the actual call. It means that by default1127 // llvm will create export register of the wrong type (always i32 in our1128 // case). So instead we need to create export register with correct type1129 // manually.1130 // TODO: To eliminate this problem we can remove gc.result intrinsics1131 // completely and make statepoint call to return a tuple.1132 Type *RetTy = GCResultLocality.second->getType();1133 Register Reg = FuncInfo.CreateRegs(RetTy);1134 RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(),1135 DAG.getDataLayout(), Reg, RetTy,1136 I.getCallingConv());1137 SDValue Chain = DAG.getEntryNode();1138 1139 RFV.getCopyToRegs(ReturnValue, DAG, getCurSDLoc(), Chain, nullptr);1140 PendingExports.push_back(Chain);1141 FuncInfo.ValueMap[&I] = Reg;1142}1143 1144void SelectionDAGBuilder::LowerCallSiteWithDeoptBundleImpl(1145 const CallBase *Call, SDValue Callee, const BasicBlock *EHPadBB,1146 bool VarArgDisallowed, bool ForceVoidReturnTy) {1147 StatepointLoweringInfo SI(DAG);1148 unsigned ArgBeginIndex = Call->arg_begin() - Call->op_begin();1149 populateCallLoweringInfo(1150 SI.CLI, Call, ArgBeginIndex, Call->arg_size(), Callee,1151 ForceVoidReturnTy ? Type::getVoidTy(*DAG.getContext()) : Call->getType(),1152 Call->getAttributes().getRetAttrs(), /*IsPatchPoint=*/false);1153 if (!VarArgDisallowed)1154 SI.CLI.IsVarArg = Call->getFunctionType()->isVarArg();1155 1156 auto DeoptBundle = *Call->getOperandBundle(LLVMContext::OB_deopt);1157 1158 unsigned DefaultID = StatepointDirectives::DeoptBundleStatepointID;1159 1160 auto SD = parseStatepointDirectivesFromAttrs(Call->getAttributes());1161 SI.ID = SD.StatepointID.value_or(DefaultID);1162 SI.NumPatchBytes = SD.NumPatchBytes.value_or(0);1163 1164 SI.DeoptState =1165 ArrayRef<const Use>(DeoptBundle.Inputs.begin(), DeoptBundle.Inputs.end());1166 SI.StatepointFlags = static_cast<uint64_t>(StatepointFlags::None);1167 SI.EHPadBB = EHPadBB;1168 1169 // NB! The GC arguments are deliberately left empty.1170 1171 LLVM_DEBUG(dbgs() << "Lowering call with deopt bundle " << *Call << "\n");1172 if (SDValue ReturnVal = LowerAsSTATEPOINT(SI)) {1173 ReturnVal = lowerRangeToAssertZExt(DAG, *Call, ReturnVal);1174 setValue(Call, ReturnVal);1175 }1176}1177 1178void SelectionDAGBuilder::LowerCallSiteWithDeoptBundle(1179 const CallBase *Call, SDValue Callee, const BasicBlock *EHPadBB) {1180 LowerCallSiteWithDeoptBundleImpl(Call, Callee, EHPadBB,1181 /* VarArgDisallowed = */ false,1182 /* ForceVoidReturnTy = */ false);1183}1184 1185void SelectionDAGBuilder::visitGCResult(const GCResultInst &CI) {1186 // The result value of the gc_result is simply the result of the actual1187 // call. We've already emitted this, so just grab the value.1188 const Value *SI = CI.getStatepoint();1189 assert((isa<GCStatepointInst>(SI) || isa<UndefValue>(SI)) &&1190 "GetStatepoint must return one of two types");1191 if (isa<UndefValue>(SI))1192 return;1193 1194 if (cast<GCStatepointInst>(SI)->getParent() == CI.getParent()) {1195 setValue(&CI, getValue(SI));1196 return;1197 }1198 // Statepoint is in different basic block so we should have stored call1199 // result in a virtual register.1200 // We can not use default getValue() functionality to copy value from this1201 // register because statepoint and actual call return types can be1202 // different, and getValue() will use CopyFromReg of the wrong type,1203 // which is always i32 in our case.1204 Type *RetTy = CI.getType();1205 SDValue CopyFromReg = getCopyFromRegs(SI, RetTy);1206 1207 assert(CopyFromReg.getNode());1208 setValue(&CI, CopyFromReg);1209}1210 1211void SelectionDAGBuilder::visitGCRelocate(const GCRelocateInst &Relocate) {1212 const Value *Statepoint = Relocate.getStatepoint();1213#ifndef NDEBUG1214 // Consistency check1215 // We skip this check for relocates not in the same basic block as their1216 // statepoint. It would be too expensive to preserve validation info through1217 // different basic blocks.1218 assert((isa<GCStatepointInst>(Statepoint) || isa<UndefValue>(Statepoint)) &&1219 "GetStatepoint must return one of two types");1220 if (isa<UndefValue>(Statepoint))1221 return;1222 1223 if (cast<GCStatepointInst>(Statepoint)->getParent() == Relocate.getParent())1224 StatepointLowering.relocCallVisited(Relocate);1225#endif1226 1227 const Value *DerivedPtr = Relocate.getDerivedPtr();1228 auto &RelocationMap =1229 FuncInfo.StatepointRelocationMaps[cast<GCStatepointInst>(Statepoint)];1230 auto SlotIt = RelocationMap.find(&Relocate);1231 assert(SlotIt != RelocationMap.end() && "Relocating not lowered gc value");1232 const RecordType &Record = SlotIt->second;1233 1234 // If relocation was done via virtual register..1235 if (Record.type == RecordType::SDValueNode) {1236 assert(cast<GCStatepointInst>(Statepoint)->getParent() ==1237 Relocate.getParent() &&1238 "Nonlocal gc.relocate mapped via SDValue");1239 SDValue SDV = StatepointLowering.getLocation(getValue(DerivedPtr));1240 assert(SDV.getNode() && "empty SDValue");1241 setValue(&Relocate, SDV);1242 return;1243 }1244 if (Record.type == RecordType::VReg) {1245 Register InReg = Record.payload.Reg;1246 RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(),1247 DAG.getDataLayout(), InReg, Relocate.getType(),1248 std::nullopt); // This is not an ABI copy.1249 // We generate copy to/from regs even for local uses, hence we must1250 // chain with current root to ensure proper ordering of copies w.r.t.1251 // statepoint.1252 SDValue Chain = DAG.getRoot();1253 SDValue Relocation = RFV.getCopyFromRegs(DAG, FuncInfo, getCurSDLoc(),1254 Chain, nullptr, nullptr);1255 setValue(&Relocate, Relocation);1256 return;1257 }1258 1259 if (Record.type == RecordType::Spill) {1260 unsigned Index = Record.payload.FI;1261 SDValue SpillSlot = DAG.getFrameIndex(Index, getFrameIndexTy());1262 1263 // All the reloads are independent and are reading memory only modified by1264 // statepoints (i.e. no other aliasing stores); informing SelectionDAG of1265 // this lets CSE kick in for free and allows reordering of1266 // instructions if possible. The lowering for statepoint sets the root,1267 // so this is ordering all reloads with the either1268 // a) the statepoint node itself, or1269 // b) the entry of the current block for an invoke statepoint.1270 const SDValue Chain = DAG.getRoot(); // != Builder.getRoot()1271 1272 auto &MF = DAG.getMachineFunction();1273 auto &MFI = MF.getFrameInfo();1274 auto PtrInfo = MachinePointerInfo::getFixedStack(MF, Index);1275 auto *LoadMMO = MF.getMachineMemOperand(PtrInfo, MachineMemOperand::MOLoad,1276 MFI.getObjectSize(Index),1277 MFI.getObjectAlign(Index));1278 1279 auto LoadVT = DAG.getTargetLoweringInfo().getValueType(DAG.getDataLayout(),1280 Relocate.getType());1281 1282 SDValue SpillLoad =1283 DAG.getLoad(LoadVT, getCurSDLoc(), Chain, SpillSlot, LoadMMO);1284 PendingLoads.push_back(SpillLoad.getValue(1));1285 1286 assert(SpillLoad.getNode());1287 setValue(&Relocate, SpillLoad);1288 return;1289 }1290 1291 assert(Record.type == RecordType::NoRelocate);1292 SDValue SD = getValue(DerivedPtr);1293 1294 if (SD.isUndef() && SD.getValueType().getSizeInBits() <= 64) {1295 // Lowering relocate(undef) as arbitrary constant. Current constant value1296 // is chosen such that it's unlikely to be a valid pointer.1297 setValue(&Relocate, DAG.getConstant(0xFEFEFEFE, SDLoc(SD), MVT::i64));1298 return;1299 }1300 1301 // We didn't need to spill these special cases (constants and allocas).1302 // See the handling in spillIncomingValueForStatepoint for detail.1303 setValue(&Relocate, SD);1304}1305 1306void SelectionDAGBuilder::LowerDeoptimizeCall(const CallInst *CI) {1307 const auto &TLI = DAG.getTargetLoweringInfo();1308 SDValue Callee = DAG.getExternalSymbol(TLI.getLibcallName(RTLIB::DEOPTIMIZE),1309 TLI.getPointerTy(DAG.getDataLayout()));1310 1311 // We don't lower calls to __llvm_deoptimize as varargs, but as a regular1312 // call. We also do not lower the return value to any virtual register, and1313 // change the immediately following return to a trap instruction.1314 LowerCallSiteWithDeoptBundleImpl(CI, Callee, /* EHPadBB = */ nullptr,1315 /* VarArgDisallowed = */ true,1316 /* ForceVoidReturnTy = */ true);1317}1318 1319void SelectionDAGBuilder::LowerDeoptimizingReturn() {1320 // We do not lower the return value from llvm.deoptimize to any virtual1321 // register, and change the immediately following return to a trap1322 // instruction.1323 if (DAG.getTarget().Options.TrapUnreachable)1324 DAG.setRoot(1325 DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot()));1326}1327