1 //===-- StatepointLowering.cpp - SDAGBuilder's statepoint code -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file includes support code use by SelectionDAGBuilder when lowering a
11 // statepoint sequence in SelectionDAG IR.
13 //===----------------------------------------------------------------------===//
15 #include "StatepointLowering.h"
16 #include "SelectionDAGBuilder.h"
17 #include "llvm/ADT/SmallSet.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/CodeGen/FunctionLoweringInfo.h"
20 #include "llvm/CodeGen/GCStrategy.h"
21 #include "llvm/CodeGen/SelectionDAG.h"
22 #include "llvm/CodeGen/StackMaps.h"
23 #include "llvm/IR/CallingConv.h"
24 #include "llvm/IR/Instructions.h"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/IR/Intrinsics.h"
27 #include "llvm/IR/Statepoint.h"
28 #include "llvm/Target/TargetLowering.h"
32 #define DEBUG_TYPE "statepoint-lowering"
34 STATISTIC(NumSlotsAllocatedForStatepoints,
35 "Number of stack slots allocated for statepoints");
36 STATISTIC(NumOfStatepoints, "Number of statepoint nodes encountered");
37 STATISTIC(StatepointMaxSlotsRequired,
38 "Maximum number of stack slots required for a singe statepoint");
41 StatepointLoweringState::startNewStatepoint(SelectionDAGBuilder &Builder) {
43 assert(PendingGCRelocateCalls.empty() &&
44 "Trying to visit statepoint before finished processing previous one");
46 RelocLocations.clear();
47 NextSlotToAllocate = 0;
48 // Need to resize this on each safepoint - we need the two to stay in
49 // sync and the clear patterns of a SelectionDAGBuilder have no relation
50 // to FunctionLoweringInfo.
51 AllocatedStackSlots.resize(Builder.FuncInfo.StatepointStackSlots.size());
52 for (size_t i = 0; i < AllocatedStackSlots.size(); i++) {
53 AllocatedStackSlots[i] = false;
56 void StatepointLoweringState::clear() {
58 RelocLocations.clear();
59 AllocatedStackSlots.clear();
60 assert(PendingGCRelocateCalls.empty() &&
61 "cleared before statepoint sequence completed");
65 StatepointLoweringState::allocateStackSlot(EVT ValueType,
66 SelectionDAGBuilder &Builder) {
68 NumSlotsAllocatedForStatepoints++;
70 // The basic scheme here is to first look for a previously created stack slot
71 // which is not in use (accounting for the fact arbitrary slots may already
72 // be reserved), or to create a new stack slot and use it.
74 // If this doesn't succeed in 40000 iterations, something is seriously wrong
75 for (int i = 0; i < 40000; i++) {
76 assert(Builder.FuncInfo.StatepointStackSlots.size() ==
77 AllocatedStackSlots.size() &&
79 const size_t NumSlots = AllocatedStackSlots.size();
80 assert(NextSlotToAllocate <= NumSlots && "broken invariant");
82 if (NextSlotToAllocate >= NumSlots) {
83 assert(NextSlotToAllocate == NumSlots);
85 if (NumSlots + 1 > StatepointMaxSlotsRequired) {
86 StatepointMaxSlotsRequired = NumSlots + 1;
89 SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType);
90 const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
91 Builder.FuncInfo.StatepointStackSlots.push_back(FI);
92 AllocatedStackSlots.push_back(true);
95 if (!AllocatedStackSlots[NextSlotToAllocate]) {
96 const int FI = Builder.FuncInfo.StatepointStackSlots[NextSlotToAllocate];
97 AllocatedStackSlots[NextSlotToAllocate] = true;
98 return Builder.DAG.getFrameIndex(FI, ValueType);
100 // Note: We deliberately choose to advance this only on the failing path.
101 // Doing so on the suceeding path involes a bit of complexity that caused a
102 // minor bug previously. Unless performance shows this matters, please
103 // keep this code as simple as possible.
104 NextSlotToAllocate++;
106 llvm_unreachable("infinite loop?");
109 /// Try to find existing copies of the incoming values in stack slots used for
110 /// statepoint spilling. If we can find a spill slot for the incoming value,
111 /// mark that slot as allocated, and reuse the same slot for this safepoint.
112 /// This helps to avoid series of loads and stores that only serve to resuffle
113 /// values on the stack between calls.
114 static void reservePreviousStackSlotForValue(SDValue Incoming,
115 SelectionDAGBuilder &Builder) {
117 if (isa<ConstantSDNode>(Incoming) || isa<FrameIndexSDNode>(Incoming)) {
118 // We won't need to spill this, so no need to check for previously
119 // allocated stack slots
123 SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);
125 // duplicates in input
129 // Search back for the load from a stack slot pattern to find the original
130 // slot we allocated for this value. We could extend this to deal with
131 // simple modification patterns, but simple dealing with trivial load/store
132 // sequences helps a lot already.
133 if (LoadSDNode *Load = dyn_cast<LoadSDNode>(Incoming)) {
134 if (auto *FI = dyn_cast<FrameIndexSDNode>(Load->getBasePtr())) {
135 const int Index = FI->getIndex();
136 auto Itr = std::find(Builder.FuncInfo.StatepointStackSlots.begin(),
137 Builder.FuncInfo.StatepointStackSlots.end(), Index);
138 if (Itr == Builder.FuncInfo.StatepointStackSlots.end()) {
139 // not one of the lowering stack slots, can't reuse!
140 // TODO: Actually, we probably could reuse the stack slot if the value
141 // hasn't changed at all, but we'd need to look for intervening writes
144 // This is one of our dedicated lowering slots
146 std::distance(Builder.FuncInfo.StatepointStackSlots.begin(), Itr);
147 if (Builder.StatepointLowering.isStackSlotAllocated(Offset)) {
148 // stack slot already assigned to someone else, can't use it!
149 // TODO: currently we reserve space for gc arguments after doing
150 // normal allocation for deopt arguments. We should reserve for
151 // _all_ deopt and gc arguments, then start allocating. This
152 // will prevent some moves being inserted when vm state changes,
153 // but gc state doesn't between two calls.
156 // Reserve this stack slot
157 Builder.StatepointLowering.reserveStackSlot(Offset);
160 // Cache this slot so we find it when going through the normal
163 Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType());
165 Builder.StatepointLowering.setLocation(Incoming, Loc);
169 // TODO: handle case where a reloaded value flows through a phi to
170 // another safepoint. e.g.
173 // bb2: % pred: bb1, bb3, bb4, etc.
174 // a_phi = phi(a', ...)
175 // statepoint ... a_phi
176 // NOTE: This will require reasoning about cross basic block values. This is
177 // decidedly non trivial and this might not be the right place to do it. We
178 // don't really have the information we need here...
180 // TODO: handle simple updates. If a value is modified and the original
181 // value is no longer live, it would be nice to put the modified value in the
182 // same slot. This allows folding of the memory accesses for some
183 // instructions types (like an increment).
189 /// Remove any duplicate (as SDValues) from the derived pointer pairs. This
190 /// is not required for correctness. It's purpose is to reduce the size of
191 /// StackMap section. It has no effect on the number of spill slots required
192 /// or the actual lowering.
193 static void removeDuplicatesGCPtrs(SmallVectorImpl<const Value *> &Bases,
194 SmallVectorImpl<const Value *> &Ptrs,
195 SmallVectorImpl<const Value *> &Relocs,
196 SelectionDAGBuilder &Builder) {
198 // This is horribly ineffecient, but I don't care right now
199 SmallSet<SDValue, 64> Seen;
201 SmallVector<const Value *, 64> NewBases, NewPtrs, NewRelocs;
202 for (size_t i = 0; i < Ptrs.size(); i++) {
203 SDValue SD = Builder.getValue(Ptrs[i]);
204 // Only add non-duplicates
205 if (Seen.count(SD) == 0) {
206 NewBases.push_back(Bases[i]);
207 NewPtrs.push_back(Ptrs[i]);
208 NewRelocs.push_back(Relocs[i]);
212 assert(Bases.size() >= NewBases.size());
213 assert(Ptrs.size() >= NewPtrs.size());
214 assert(Relocs.size() >= NewRelocs.size());
218 assert(Ptrs.size() == Bases.size());
219 assert(Ptrs.size() == Relocs.size());
222 /// Extract call from statepoint, lower it and return pointer to the
223 /// call node. Also update NodeMap so that getValue(statepoint) will
224 /// reference lowered call result
225 static SDNode *lowerCallFromStatepoint(const CallInst &CI,
226 SelectionDAGBuilder &Builder) {
228 assert(Intrinsic::experimental_gc_statepoint ==
229 dyn_cast<IntrinsicInst>(&CI)->getIntrinsicID() &&
230 "function called must be the statepoint function");
232 ImmutableStatepoint StatepointOperands(&CI);
234 // Lower the actual call itself - This is a bit of a hack, but we want to
235 // avoid modifying the actual lowering code. This is similiar in intent to
236 // the LowerCallOperands mechanism used by PATCHPOINT, but is structured
237 // differently. Hopefully, this is slightly more robust w.r.t. calling
238 // convention, return values, and other function attributes.
239 Value *ActualCallee = const_cast<Value *>(StatepointOperands.actualCallee());
241 std::vector<Value *> Args;
242 CallInst::const_op_iterator arg_begin = StatepointOperands.call_args_begin();
243 CallInst::const_op_iterator arg_end = StatepointOperands.call_args_end();
244 Args.insert(Args.end(), arg_begin, arg_end);
245 // TODO: remove the creation of a new instruction! We should not be
246 // modifying the IR (even temporarily) at this point.
247 CallInst *Tmp = CallInst::Create(ActualCallee, Args);
248 Tmp->setTailCall(CI.isTailCall());
249 Tmp->setCallingConv(CI.getCallingConv());
250 Tmp->setAttributes(CI.getAttributes());
251 Builder.LowerCallTo(Tmp, Builder.getValue(ActualCallee), false);
253 // Handle the return value of the call iff any.
254 const bool HasDef = !Tmp->getType()->isVoidTy();
256 // The value of the statepoint itself will be the value of call itself.
257 // We'll replace the actually call node shortly. gc_result will grab
259 Builder.setValue(&CI, Builder.getValue(Tmp));
261 // The token value is never used from here on, just generate a poison value
262 Builder.setValue(&CI, Builder.DAG.getIntPtrConstant(-1));
264 // Remove the fake entry we created so we don't have a hanging reference
265 // after we delete this node.
266 Builder.removeValue(Tmp);
270 // Search for the call node
271 // The following code is essentially reverse engineering X86's
273 SDNode *CallNode = nullptr;
275 // We just emitted a call, so it should be last thing generated
276 SDValue Chain = Builder.DAG.getRoot();
278 // Find closest CALLSEQ_END walking back through lowered nodes if needed
279 SDNode *CallEnd = Chain.getNode();
281 while (CallEnd->getOpcode() != ISD::CALLSEQ_END) {
282 CallEnd = CallEnd->getGluedNode();
283 assert(CallEnd && "Can not find call node");
284 assert(Sanity < 20 && "should have found call end already");
287 assert(CallEnd->getOpcode() == ISD::CALLSEQ_END &&
288 "Expected a callseq node.");
289 assert(CallEnd->getGluedNode());
291 // Step back inside the CALLSEQ
292 CallNode = CallEnd->getGluedNode();
296 /// Callect all gc pointers coming into statepoint intrinsic, clean them up,
297 /// and return two arrays:
298 /// Bases - base pointers incoming to this statepoint
299 /// Ptrs - derived pointers incoming to this statepoint
300 /// Relocs - the gc_relocate corresponding to each base/ptr pair
301 /// Elements of this arrays should be in one-to-one correspondence with each
302 /// other i.e Bases[i], Ptrs[i] are from the same gcrelocate call
304 getIncomingStatepointGCValues(SmallVectorImpl<const Value *> &Bases,
305 SmallVectorImpl<const Value *> &Ptrs,
306 SmallVectorImpl<const Value *> &Relocs,
307 ImmutableCallSite Statepoint,
308 SelectionDAGBuilder &Builder) {
309 // Search for relocated pointers. Note that working backwards from the
310 // gc_relocates ensures that we only get pairs which are actually relocated
311 // and used after the statepoint.
312 // TODO: This logic should probably become a utility function in Statepoint.h
313 for (const User *U : cast<CallInst>(Statepoint.getInstruction())->users()) {
314 if (!isGCRelocate(U)) {
317 GCRelocateOperands relocateOpers(U);
318 Relocs.push_back(cast<Value>(U));
319 Bases.push_back(relocateOpers.basePtr());
320 Ptrs.push_back(relocateOpers.derivedPtr());
323 // Remove any redundant llvm::Values which map to the same SDValue as another
324 // input. Also has the effect of removing duplicates in the original
325 // llvm::Value input list as well. This is a useful optimization for
326 // reducing the size of the StackMap section. It has no other impact.
327 removeDuplicatesGCPtrs(Bases, Ptrs, Relocs, Builder);
329 assert(Bases.size() == Ptrs.size() && Ptrs.size() == Relocs.size());
332 /// Spill a value incoming to the statepoint. It might be either part of
334 /// or gcstate. In both cases unconditionally spill it on the stack unless it
335 /// is a null constant. Return pair with first element being frame index
336 /// containing saved value and second element with outgoing chain from the
338 static std::pair<SDValue, SDValue>
339 spillIncomingStatepointValue(SDValue Incoming, SDValue Chain,
340 SelectionDAGBuilder &Builder) {
341 SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);
343 // Emit new store if we didn't do it for this ptr before
344 if (!Loc.getNode()) {
345 Loc = Builder.StatepointLowering.allocateStackSlot(Incoming.getValueType(),
347 assert(isa<FrameIndexSDNode>(Loc));
348 int Index = cast<FrameIndexSDNode>(Loc)->getIndex();
349 // We use TargetFrameIndex so that isel will not select it into LEA
350 Loc = Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType());
352 // TODO: We can create TokenFactor node instead of
353 // chaining stores one after another, this may allow
354 // a bit more optimal scheduling for them
355 Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc,
356 MachinePointerInfo::getFixedStack(Index),
359 Builder.StatepointLowering.setLocation(Incoming, Loc);
362 assert(Loc.getNode());
363 return std::make_pair(Loc, Chain);
366 /// Lower a single value incoming to a statepoint node. This value can be
367 /// either a deopt value or a gc value, the handling is the same. We special
368 /// case constants and allocas, then fall back to spilling if required.
369 static void lowerIncomingStatepointValue(SDValue Incoming,
370 SmallVectorImpl<SDValue> &Ops,
371 SelectionDAGBuilder &Builder) {
372 SDValue Chain = Builder.getRoot();
374 if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) {
375 // If the original value was a constant, make sure it gets recorded as
376 // such in the stackmap. This is required so that the consumer can
377 // parse any internal format to the deopt state. It also handles null
378 // pointers and other constant pointers in GC states
380 Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
381 Ops.push_back(Builder.DAG.getTargetConstant(C->getSExtValue(), MVT::i64));
382 } else if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) {
383 // This handles allocas as arguments to the statepoint
384 const TargetLowering &TLI = Builder.DAG.getTargetLoweringInfo();
386 Builder.DAG.getTargetFrameIndex(FI->getIndex(), TLI.getPointerTy()));
388 // Otherwise, locate a spill slot and explicitly spill it so it
389 // can be found by the runtime later. We currently do not support
390 // tracking values through callee saved registers to their eventual
391 // spill location. This would be a useful optimization, but would
392 // need to be optional since it requires a lot of complexity on the
393 // runtime side which not all would support.
394 std::pair<SDValue, SDValue> Res =
395 spillIncomingStatepointValue(Incoming, Chain, Builder);
396 Ops.push_back(Res.first);
400 Builder.DAG.setRoot(Chain);
403 /// Lower deopt state and gc pointer arguments of the statepoint. The actual
404 /// lowering is described in lowerIncomingStatepointValue. This function is
405 /// responsible for lowering everything in the right position and playing some
406 /// tricks to avoid redundant stack manipulation where possible. On
407 /// completion, 'Ops' will contain ready to use operands for machine code
408 /// statepoint. The chain nodes will have already been created and the DAG root
409 /// will be set to the last value spilled (if any were).
410 static void lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,
411 ImmutableStatepoint Statepoint,
412 SelectionDAGBuilder &Builder) {
414 // Lower the deopt and gc arguments for this statepoint. Layout will
415 // be: deopt argument length, deopt arguments.., gc arguments...
417 SmallVector<const Value *, 64> Bases, Ptrs, Relocations;
418 getIncomingStatepointGCValues(Bases, Ptrs, Relocations,
419 Statepoint.getCallSite(), Builder);
422 // Check that each of the gc pointer and bases we've gotten out of the
423 // safepoint is something the strategy thinks might be a pointer into the GC
424 // heap. This is basically just here to help catch errors during statepoint
425 // insertion. TODO: This should actually be in the Verifier, but we can't get
426 // to the GCStrategy from there (yet).
428 GCStrategy &S = Builder.GFI->getStrategy();
429 for (const Value *V : Bases) {
430 auto Opt = S.isGCManagedPointer(V);
431 if (Opt.hasValue()) {
432 assert(Opt.getValue() &&
433 "non gc managed base pointer found in statepoint");
436 for (const Value *V : Ptrs) {
437 auto Opt = S.isGCManagedPointer(V);
438 if (Opt.hasValue()) {
439 assert(Opt.getValue() &&
440 "non gc managed derived pointer found in statepoint");
443 for (const Value *V : Relocations) {
444 auto Opt = S.isGCManagedPointer(V);
445 if (Opt.hasValue()) {
446 assert(Opt.getValue() && "non gc managed pointer relocated");
454 // Before we actually start lowering (and allocating spill slots for values),
455 // reserve any stack slots which we judge to be profitable to reuse for a
456 // particular value. This is purely an optimization over the code below and
457 // doesn't change semantics at all. It is important for performance that we
458 // reserve slots for both deopt and gc values before lowering either.
459 for (auto I = Statepoint.vm_state_begin() + 1, E = Statepoint.vm_state_end();
462 SDValue Incoming = Builder.getValue(V);
463 reservePreviousStackSlotForValue(Incoming, Builder);
465 for (unsigned i = 0; i < Bases.size() * 2; ++i) {
466 // Even elements will contain base, odd elements - derived ptr
467 const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2];
468 SDValue Incoming = Builder.getValue(V);
469 reservePreviousStackSlotForValue(Incoming, Builder);
472 // First, prefix the list with the number of unique values to be
473 // lowered. Note that this is the number of *Values* not the
474 // number of SDValues required to lower them.
475 const int NumVMSArgs = Statepoint.numTotalVMSArgs();
477 Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
478 Ops.push_back(Builder.DAG.getTargetConstant(NumVMSArgs, MVT::i64));
480 assert(NumVMSArgs + 1 == std::distance(Statepoint.vm_state_begin(),
481 Statepoint.vm_state_end()));
483 // The vm state arguments are lowered in an opaque manner. We do
484 // not know what type of values are contained within. We skip the
485 // first one since that happens to be the total number we lowered
486 // explicitly just above. We could have left it in the loop and
487 // not done it explicitly, but it's far easier to understand this
489 for (auto I = Statepoint.vm_state_begin() + 1, E = Statepoint.vm_state_end();
492 SDValue Incoming = Builder.getValue(V);
493 lowerIncomingStatepointValue(Incoming, Ops, Builder);
496 // Finally, go ahead and lower all the gc arguments. There's no prefixed
497 // length for this one. After lowering, we'll have the base and pointer
498 // arrays interwoven with each (lowered) base pointer immediately followed by
499 // it's (lowered) derived pointer. i.e
500 // (base[0], ptr[0], base[1], ptr[1], ...)
501 for (unsigned i = 0; i < Bases.size() * 2; ++i) {
502 // Even elements will contain base, odd elements - derived ptr
503 const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2];
504 SDValue Incoming = Builder.getValue(V);
505 lowerIncomingStatepointValue(Incoming, Ops, Builder);
508 void SelectionDAGBuilder::visitStatepoint(const CallInst &CI) {
509 // The basic scheme here is that information about both the original call and
510 // the safepoint is encoded in the CallInst. We create a temporary call and
511 // lower it, then reverse engineer the calling sequence.
513 // Check some preconditions for sanity
514 assert(isStatepoint(&CI) &&
515 "function called must be the statepoint function");
518 StatepointLowering.startNewStatepoint(*this);
522 for (const User *U : CI.users()) {
523 const CallInst *Call = cast<CallInst>(U);
524 if (isGCRelocate(Call))
525 StatepointLowering.scheduleRelocCall(*Call);
529 ImmutableStatepoint ISP(&CI);
531 // If this is a malformed statepoint, report it early to simplify debugging.
532 // This should catch any IR level mistake that's made when constructing or
533 // transforming statepoints.
536 // Check that the associated GCStrategy expects to encounter statepoints.
537 // TODO: This if should become an assert. For now, we allow the GCStrategy
538 // to be optional for backwards compatibility. This will only last a short
539 // period (i.e. a couple of weeks).
541 assert(GFI->getStrategy().useStatepoints() &&
542 "GCStrategy does not expect to encounter statepoints");
547 // Lower statepoint vmstate and gcstate arguments
548 SmallVector<SDValue, 10> LoweredArgs;
549 lowerStatepointMetaArgs(LoweredArgs, ISP, *this);
551 // Get call node, we will replace it later with statepoint
552 SDNode *CallNode = lowerCallFromStatepoint(CI, *this);
554 // Construct the actual STATEPOINT node with all the appropriate arguments
555 // and return values.
557 // TODO: Currently, all of these operands are being marked as read/write in
558 // PrologEpilougeInserter.cpp, we should special case the VMState arguments
559 // and flags to be read-only.
560 SmallVector<SDValue, 40> Ops;
562 // Calculate and push starting position of vmstate arguments
563 // Call Node: Chain, Target, {Args}, RegMask, [Glue]
565 if (CallNode->getGluedNode()) {
566 // Glue is always last operand
567 Glue = CallNode->getOperand(CallNode->getNumOperands() - 1);
569 // Get number of arguments incoming directly into call node
570 unsigned NumCallRegArgs =
571 CallNode->getNumOperands() - (Glue.getNode() ? 4 : 3);
572 Ops.push_back(DAG.getTargetConstant(NumCallRegArgs, MVT::i32));
575 SDValue CallTarget = SDValue(CallNode->getOperand(1).getNode(), 0);
576 Ops.push_back(CallTarget);
578 // Add call arguments
579 // Get position of register mask in the call
580 SDNode::op_iterator RegMaskIt;
582 RegMaskIt = CallNode->op_end() - 2;
584 RegMaskIt = CallNode->op_end() - 1;
585 Ops.insert(Ops.end(), CallNode->op_begin() + 2, RegMaskIt);
587 // Add a leading constant argument with the Flags and the calling convention
589 CallingConv::ID CallConv = CI.getCallingConv();
590 int Flags = dyn_cast<ConstantInt>(CI.getArgOperand(2))->getZExtValue();
591 assert(Flags == 0 && "not expected to be used");
592 Ops.push_back(DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
594 DAG.getTargetConstant(Flags | ((unsigned)CallConv << 1), MVT::i64));
596 // Insert all vmstate and gcstate arguments
597 Ops.insert(Ops.end(), LoweredArgs.begin(), LoweredArgs.end());
599 // Add register mask from call node
600 Ops.push_back(*RegMaskIt);
603 Ops.push_back(CallNode->getOperand(0));
605 // Same for the glue, but we add it only if original call had it
609 // Compute return values
610 SmallVector<EVT, 21> ValueVTs;
611 ValueVTs.push_back(MVT::Other);
612 ValueVTs.push_back(MVT::Glue); // provide a glue output since we consume one
613 // as input. This allows someone else to chain
615 SDVTList NodeTys = DAG.getVTList(ValueVTs);
617 SDNode *StatepointMCNode = DAG.getMachineNode(TargetOpcode::STATEPOINT,
618 getCurSDLoc(), NodeTys, Ops);
620 // Replace original call
621 DAG.ReplaceAllUsesWith(CallNode, StatepointMCNode); // This may update Root
622 // Remove originall call node
623 DAG.DeleteNode(CallNode);
625 // DON'T set the root - under the assumption that it's already set past the
626 // inserted node we created.
628 // TODO: A better future implementation would be to emit a single variable
629 // argument, variable return value STATEPOINT node here and then hookup the
630 // return value of each gc.relocate to the respective output of the
631 // previously emitted STATEPOINT value. Unfortunately, this doesn't appear
632 // to actually be possible today.
635 void SelectionDAGBuilder::visitGCResult(const CallInst &CI) {
636 // The result value of the gc_result is simply the result of the actual
637 // call. We've already emitted this, so just grab the value.
638 Instruction *I = cast<Instruction>(CI.getArgOperand(0));
639 assert(isStatepoint(I) &&
640 "first argument must be a statepoint token");
642 setValue(&CI, getValue(I));
645 void SelectionDAGBuilder::visitGCRelocate(const CallInst &CI) {
648 StatepointLowering.relocCallVisited(CI);
651 GCRelocateOperands relocateOpers(&CI);
652 SDValue SD = getValue(relocateOpers.derivedPtr());
654 if (isa<ConstantSDNode>(SD) || isa<FrameIndexSDNode>(SD)) {
655 // We didn't need to spill these special cases (constants and allocas).
656 // See the handling in spillIncomingValueForStatepoint for detail.
661 SDValue Loc = StatepointLowering.getRelocLocation(SD);
662 // Emit new load if we did not emit it before
663 if (!Loc.getNode()) {
664 SDValue SpillSlot = StatepointLowering.getLocation(SD);
665 int FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
667 // Be conservative: flush all pending loads
668 // TODO: Probably we can be less restrictive on this,
669 // it may allow more scheduling opprtunities
670 SDValue Chain = getRoot();
672 Loc = DAG.getLoad(SpillSlot.getValueType(), getCurSDLoc(), Chain,
673 SpillSlot, MachinePointerInfo::getFixedStack(FI), false,
676 StatepointLowering.setRelocLocation(SD, Loc);
678 // Again, be conservative, don't emit pending loads
679 DAG.setRoot(Loc.getValue(1));
682 assert(Loc.getNode());