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/SelectionDAG.h"
21 #include "llvm/CodeGen/StackMaps.h"
22 #include "llvm/IR/CallingConv.h"
23 #include "llvm/IR/Instructions.h"
24 #include "llvm/IR/IntrinsicInst.h"
25 #include "llvm/IR/Intrinsics.h"
26 #include "llvm/IR/Statepoint.h"
27 #include "llvm/Target/TargetLowering.h"
31 #define DEBUG_TYPE "statepoint-lowering"
33 STATISTIC(NumSlotsAllocatedForStatepoints,
34 "Number of stack slots allocated for statepoints");
35 STATISTIC(NumOfStatepoints, "Number of statepoint nodes encountered");
36 STATISTIC(StatepointMaxSlotsRequired,
37 "Maximum number of stack slots required for a singe statepoint");
40 StatepointLoweringState::startNewStatepoint(SelectionDAGBuilder &Builder) {
42 assert(PendingGCRelocateCalls.empty() &&
43 "Trying to visit statepoint before finished processing previous one");
45 RelocLocations.clear();
46 NextSlotToAllocate = 0;
47 // Need to resize this on each safepoint - we need the two to stay in
48 // sync and the clear patterns of a SelectionDAGBuilder have no relation
49 // to FunctionLoweringInfo.
50 AllocatedStackSlots.resize(Builder.FuncInfo.StatepointStackSlots.size());
51 for (size_t i = 0; i < AllocatedStackSlots.size(); i++) {
52 AllocatedStackSlots[i] = false;
55 void StatepointLoweringState::clear() {
57 RelocLocations.clear();
58 AllocatedStackSlots.clear();
59 assert(PendingGCRelocateCalls.empty() &&
60 "cleared before statepoint sequence completed");
64 StatepointLoweringState::allocateStackSlot(EVT ValueType,
65 SelectionDAGBuilder &Builder) {
67 NumSlotsAllocatedForStatepoints++;
69 // The basic scheme here is to first look for a previously created stack slot
70 // which is not in use (accounting for the fact arbitrary slots may already
71 // be reserved), or to create a new stack slot and use it.
73 // If this doesn't succeed in 40000 iterations, something is seriously wrong
74 for (int i = 0; i < 40000; i++) {
75 assert(Builder.FuncInfo.StatepointStackSlots.size() ==
76 AllocatedStackSlots.size() &&
78 const size_t NumSlots = AllocatedStackSlots.size();
79 assert(NextSlotToAllocate <= NumSlots && "broken invariant");
81 if (NextSlotToAllocate >= NumSlots) {
82 assert(NextSlotToAllocate == NumSlots);
84 if (NumSlots + 1 > StatepointMaxSlotsRequired) {
85 StatepointMaxSlotsRequired = NumSlots + 1;
88 SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType);
89 const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
90 Builder.FuncInfo.StatepointStackSlots.push_back(FI);
91 AllocatedStackSlots.push_back(true);
94 if (!AllocatedStackSlots[NextSlotToAllocate]) {
95 const int FI = Builder.FuncInfo.StatepointStackSlots[NextSlotToAllocate];
96 AllocatedStackSlots[NextSlotToAllocate] = true;
97 return Builder.DAG.getFrameIndex(FI, ValueType);
99 // Note: We deliberately choose to advance this only on the failing path.
100 // Doing so on the suceeding path involes a bit of complexity that caused a
101 // minor bug previously. Unless performance shows this matters, please
102 // keep this code as simple as possible.
103 NextSlotToAllocate++;
105 llvm_unreachable("infinite loop?");
108 /// Try to find existing copies of the incoming values in stack slots used for
109 /// statepoint spilling. If we can find a spill slot for the incoming value,
110 /// mark that slot as allocated, and reuse the same slot for this safepoint.
111 /// This helps to avoid series of loads and stores that only serve to resuffle
112 /// values on the stack between calls.
113 static void reservePreviousStackSlotForValue(SDValue Incoming,
114 SelectionDAGBuilder &Builder) {
116 if (isa<ConstantSDNode>(Incoming) || isa<FrameIndexSDNode>(Incoming)) {
117 // We won't need to spill this, so no need to check for previously
118 // allocated stack slots
122 SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);
124 // duplicates in input
128 // Search back for the load from a stack slot pattern to find the original
129 // slot we allocated for this value. We could extend this to deal with
130 // simple modification patterns, but simple dealing with trivial load/store
131 // sequences helps a lot already.
132 if (LoadSDNode *Load = dyn_cast<LoadSDNode>(Incoming)) {
133 if (auto *FI = dyn_cast<FrameIndexSDNode>(Load->getBasePtr())) {
134 const int Index = FI->getIndex();
135 auto Itr = std::find(Builder.FuncInfo.StatepointStackSlots.begin(),
136 Builder.FuncInfo.StatepointStackSlots.end(), Index);
137 if (Itr == Builder.FuncInfo.StatepointStackSlots.end()) {
138 // not one of the lowering stack slots, can't reuse!
139 // TODO: Actually, we probably could reuse the stack slot if the value
140 // hasn't changed at all, but we'd need to look for intervening writes
143 // This is one of our dedicated lowering slots
145 std::distance(Builder.FuncInfo.StatepointStackSlots.begin(), Itr);
146 if (Builder.StatepointLowering.isStackSlotAllocated(Offset)) {
147 // stack slot already assigned to someone else, can't use it!
148 // TODO: currently we reserve space for gc arguments after doing
149 // normal allocation for deopt arguments. We should reserve for
150 // _all_ deopt and gc arguments, then start allocating. This
151 // will prevent some moves being inserted when vm state changes,
152 // but gc state doesn't between two calls.
155 // Reserve this stack slot
156 Builder.StatepointLowering.reserveStackSlot(Offset);
159 // Cache this slot so we find it when going through the normal
162 Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType());
164 Builder.StatepointLowering.setLocation(Incoming, Loc);
168 // TODO: handle case where a reloaded value flows through a phi to
169 // another safepoint. e.g.
172 // bb2: % pred: bb1, bb3, bb4, etc.
173 // a_phi = phi(a', ...)
174 // statepoint ... a_phi
175 // NOTE: This will require reasoning about cross basic block values. This is
176 // decidedly non trivial and this might not be the right place to do it. We
177 // don't really have the information we need here...
179 // TODO: handle simple updates. If a value is modified and the original
180 // value is no longer live, it would be nice to put the modified value in the
181 // same slot. This allows folding of the memory accesses for some
182 // instructions types (like an increment).
188 /// Remove any duplicate (as SDValues) from the derived pointer pairs. This
189 /// is not required for correctness. It's purpose is to reduce the size of
190 /// StackMap section. It has no effect on the number of spill slots required
191 /// or the actual lowering.
192 static void removeDuplicatesGCPtrs(SmallVectorImpl<const Value *> &Bases,
193 SmallVectorImpl<const Value *> &Ptrs,
194 SmallVectorImpl<const Value *> &Relocs,
195 SelectionDAGBuilder &Builder) {
197 // This is horribly ineffecient, but I don't care right now
198 SmallSet<SDValue, 64> Seen;
200 SmallVector<const Value *, 64> NewBases, NewPtrs, NewRelocs;
201 for (size_t i = 0; i < Ptrs.size(); i++) {
202 SDValue SD = Builder.getValue(Ptrs[i]);
203 // Only add non-duplicates
204 if (Seen.count(SD) == 0) {
205 NewBases.push_back(Bases[i]);
206 NewPtrs.push_back(Ptrs[i]);
207 NewRelocs.push_back(Relocs[i]);
211 assert(Bases.size() >= NewBases.size());
212 assert(Ptrs.size() >= NewPtrs.size());
213 assert(Relocs.size() >= NewRelocs.size());
217 assert(Ptrs.size() == Bases.size());
218 assert(Ptrs.size() == Relocs.size());
221 /// Extract call from statepoint, lower it and return pointer to the
222 /// call node. Also update NodeMap so that getValue(statepoint) will
223 /// reference lowered call result
224 static SDNode *lowerCallFromStatepoint(const CallInst &CI,
225 SelectionDAGBuilder &Builder) {
227 assert(Intrinsic::experimental_gc_statepoint ==
228 dyn_cast<IntrinsicInst>(&CI)->getIntrinsicID() &&
229 "function called must be the statepoint function");
231 ImmutableStatepoint StatepointOperands(&CI);
233 // Lower the actual call itself - This is a bit of a hack, but we want to
234 // avoid modifying the actual lowering code. This is similiar in intent to
235 // the LowerCallOperands mechanism used by PATCHPOINT, but is structured
236 // differently. Hopefully, this is slightly more robust w.r.t. calling
237 // convention, return values, and other function attributes.
238 Value *ActualCallee = const_cast<Value *>(StatepointOperands.actualCallee());
240 std::vector<Value *> Args;
241 CallInst::const_op_iterator arg_begin = StatepointOperands.call_args_begin();
242 CallInst::const_op_iterator arg_end = StatepointOperands.call_args_end();
243 Args.insert(Args.end(), arg_begin, arg_end);
244 // TODO: remove the creation of a new instruction! We should not be
245 // modifying the IR (even temporarily) at this point.
246 CallInst *Tmp = CallInst::Create(ActualCallee, Args);
247 Tmp->setTailCall(CI.isTailCall());
248 Tmp->setCallingConv(CI.getCallingConv());
249 Tmp->setAttributes(CI.getAttributes());
250 Builder.LowerCallTo(Tmp, Builder.getValue(ActualCallee), false);
252 // Handle the return value of the call iff any.
253 const bool HasDef = !Tmp->getType()->isVoidTy();
255 // The value of the statepoint itself will be the value of call itself.
256 // We'll replace the actually call node shortly. gc_result will grab
258 Builder.setValue(&CI, Builder.getValue(Tmp));
260 // The token value is never used from here on, just generate a poison value
261 Builder.setValue(&CI, Builder.DAG.getIntPtrConstant(-1));
263 // Remove the fake entry we created so we don't have a hanging reference
264 // after we delete this node.
265 Builder.removeValue(Tmp);
269 // Search for the call node
270 // The following code is essentially reverse engineering X86's
272 SDNode *CallNode = nullptr;
274 // We just emitted a call, so it should be last thing generated
275 SDValue Chain = Builder.DAG.getRoot();
277 // Find closest CALLSEQ_END walking back through lowered nodes if needed
278 SDNode *CallEnd = Chain.getNode();
280 while (CallEnd->getOpcode() != ISD::CALLSEQ_END) {
281 CallEnd = CallEnd->getGluedNode();
282 assert(CallEnd && "Can not find call node");
283 assert(Sanity < 20 && "should have found call end already");
286 assert(CallEnd->getOpcode() == ISD::CALLSEQ_END &&
287 "Expected a callseq node.");
288 assert(CallEnd->getGluedNode());
290 // Step back inside the CALLSEQ
291 CallNode = CallEnd->getGluedNode();
295 /// Callect all gc pointers coming into statepoint intrinsic, clean them up,
296 /// and return two arrays:
297 /// Bases - base pointers incoming to this statepoint
298 /// Ptrs - derived pointers incoming to this statepoint
299 /// Relocs - the gc_relocate corresponding to each base/ptr pair
300 /// Elements of this arrays should be in one-to-one correspondence with each
301 /// other i.e Bases[i], Ptrs[i] are from the same gcrelocate call
303 getIncomingStatepointGCValues(SmallVectorImpl<const Value *> &Bases,
304 SmallVectorImpl<const Value *> &Ptrs,
305 SmallVectorImpl<const Value *> &Relocs,
306 ImmutableCallSite Statepoint,
307 SelectionDAGBuilder &Builder) {
308 // Search for relocated pointers. Note that working backwards from the
309 // gc_relocates ensures that we only get pairs which are actually relocated
310 // and used after the statepoint.
311 // TODO: This logic should probably become a utility function in Statepoint.h
312 for (const User *U : cast<CallInst>(Statepoint.getInstruction())->users()) {
313 if (!isGCRelocate(U)) {
316 GCRelocateOperands relocateOpers(U);
317 Relocs.push_back(cast<Value>(U));
318 Bases.push_back(relocateOpers.basePtr());
319 Ptrs.push_back(relocateOpers.derivedPtr());
322 // Remove any redundant llvm::Values which map to the same SDValue as another
323 // input. Also has the effect of removing duplicates in the original
324 // llvm::Value input list as well. This is a useful optimization for
325 // reducing the size of the StackMap section. It has no other impact.
326 removeDuplicatesGCPtrs(Bases, Ptrs, Relocs, Builder);
328 assert(Bases.size() == Ptrs.size() && Ptrs.size() == Relocs.size());
331 /// Spill a value incoming to the statepoint. It might be either part of
333 /// or gcstate. In both cases unconditionally spill it on the stack unless it
334 /// is a null constant. Return pair with first element being frame index
335 /// containing saved value and second element with outgoing chain from the
337 static std::pair<SDValue, SDValue>
338 spillIncomingStatepointValue(SDValue Incoming, SDValue Chain,
339 SelectionDAGBuilder &Builder) {
340 SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);
342 // Emit new store if we didn't do it for this ptr before
343 if (!Loc.getNode()) {
344 Loc = Builder.StatepointLowering.allocateStackSlot(Incoming.getValueType(),
346 assert(isa<FrameIndexSDNode>(Loc));
347 int Index = cast<FrameIndexSDNode>(Loc)->getIndex();
348 // We use TargetFrameIndex so that isel will not select it into LEA
349 Loc = Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType());
351 // TODO: We can create TokenFactor node instead of
352 // chaining stores one after another, this may allow
353 // a bit more optimal scheduling for them
354 Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc,
355 MachinePointerInfo::getFixedStack(Index),
358 Builder.StatepointLowering.setLocation(Incoming, Loc);
361 assert(Loc.getNode());
362 return std::make_pair(Loc, Chain);
365 /// Lower a single value incoming to a statepoint node. This value can be
366 /// either a deopt value or a gc value, the handling is the same. We special
367 /// case constants and allocas, then fall back to spilling if required.
368 static void lowerIncomingStatepointValue(SDValue Incoming,
369 SmallVectorImpl<SDValue> &Ops,
370 SelectionDAGBuilder &Builder) {
371 SDValue Chain = Builder.getRoot();
373 if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) {
374 // If the original value was a constant, make sure it gets recorded as
375 // such in the stackmap. This is required so that the consumer can
376 // parse any internal format to the deopt state. It also handles null
377 // pointers and other constant pointers in GC states
379 Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
380 Ops.push_back(Builder.DAG.getTargetConstant(C->getSExtValue(), MVT::i64));
381 } else if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) {
382 // This handles allocas as arguments to the statepoint
383 const TargetLowering &TLI = Builder.DAG.getTargetLoweringInfo();
385 Builder.DAG.getTargetFrameIndex(FI->getIndex(), TLI.getPointerTy()));
387 // Otherwise, locate a spill slot and explicitly spill it so it
388 // can be found by the runtime later. We currently do not support
389 // tracking values through callee saved registers to their eventual
390 // spill location. This would be a useful optimization, but would
391 // need to be optional since it requires a lot of complexity on the
392 // runtime side which not all would support.
393 std::pair<SDValue, SDValue> Res =
394 spillIncomingStatepointValue(Incoming, Chain, Builder);
395 Ops.push_back(Res.first);
399 Builder.DAG.setRoot(Chain);
402 /// Lower deopt state and gc pointer arguments of the statepoint. The actual
403 /// lowering is described in lowerIncomingStatepointValue. This function is
404 /// responsible for lowering everything in the right position and playing some
405 /// tricks to avoid redundant stack manipulation where possible. On
406 /// completion, 'Ops' will contain ready to use operands for machine code
407 /// statepoint. The chain nodes will have already been created and the DAG root
408 /// will be set to the last value spilled (if any were).
409 static void lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,
410 ImmutableStatepoint Statepoint,
411 SelectionDAGBuilder &Builder) {
413 // Lower the deopt and gc arguments for this statepoint. Layout will
414 // be: deopt argument length, deopt arguments.., gc arguments...
416 SmallVector<const Value *, 64> Bases, Ptrs, Relocations;
417 getIncomingStatepointGCValues(Bases, Ptrs, Relocations,
418 Statepoint.getCallSite(), Builder);
420 // Before we actually start lowering (and allocating spill slots for values),
421 // reserve any stack slots which we judge to be profitable to reuse for a
422 // particular value. This is purely an optimization over the code below and
423 // doesn't change semantics at all. It is important for performance that we
424 // reserve slots for both deopt and gc values before lowering either.
425 for (auto I = Statepoint.vm_state_begin() + 1, E = Statepoint.vm_state_end();
428 SDValue Incoming = Builder.getValue(V);
429 reservePreviousStackSlotForValue(Incoming, Builder);
431 for (unsigned i = 0; i < Bases.size() * 2; ++i) {
432 // Even elements will contain base, odd elements - derived ptr
433 const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2];
434 SDValue Incoming = Builder.getValue(V);
435 reservePreviousStackSlotForValue(Incoming, Builder);
438 // First, prefix the list with the number of unique values to be
439 // lowered. Note that this is the number of *Values* not the
440 // number of SDValues required to lower them.
441 const int NumVMSArgs = Statepoint.numTotalVMSArgs();
443 Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
444 Ops.push_back(Builder.DAG.getTargetConstant(NumVMSArgs, MVT::i64));
446 assert(NumVMSArgs + 1 == std::distance(Statepoint.vm_state_begin(),
447 Statepoint.vm_state_end()));
449 // The vm state arguments are lowered in an opaque manner. We do
450 // not know what type of values are contained within. We skip the
451 // first one since that happens to be the total number we lowered
452 // explicitly just above. We could have left it in the loop and
453 // not done it explicitly, but it's far easier to understand this
455 for (auto I = Statepoint.vm_state_begin() + 1, E = Statepoint.vm_state_end();
458 SDValue Incoming = Builder.getValue(V);
459 lowerIncomingStatepointValue(Incoming, Ops, Builder);
462 // Finally, go ahead and lower all the gc arguments. There's no prefixed
463 // length for this one. After lowering, we'll have the base and pointer
464 // arrays interwoven with each (lowered) base pointer immediately followed by
465 // it's (lowered) derived pointer. i.e
466 // (base[0], ptr[0], base[1], ptr[1], ...)
467 for (unsigned i = 0; i < Bases.size() * 2; ++i) {
468 // Even elements will contain base, odd elements - derived ptr
469 const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2];
470 SDValue Incoming = Builder.getValue(V);
471 lowerIncomingStatepointValue(Incoming, Ops, Builder);
474 void SelectionDAGBuilder::visitStatepoint(const CallInst &CI) {
475 // The basic scheme here is that information about both the original call and
476 // the safepoint is encoded in the CallInst. We create a temporary call and
477 // lower it, then reverse engineer the calling sequence.
479 // Check some preconditions for sanity
480 assert(isStatepoint(&CI) &&
481 "function called must be the statepoint function");
484 StatepointLowering.startNewStatepoint(*this);
488 for (const User *U : CI.users()) {
489 const CallInst *Call = cast<CallInst>(U);
490 if (isGCRelocate(Call))
491 StatepointLowering.scheduleRelocCall(*Call);
495 ImmutableStatepoint ISP(&CI);
497 // If this is a malformed statepoint, report it early to simplify debugging.
498 // This should catch any IR level mistake that's made when constructing or
499 // transforming statepoints.
504 // Lower statepoint vmstate and gcstate arguments
505 SmallVector<SDValue, 10> LoweredArgs;
506 lowerStatepointMetaArgs(LoweredArgs, ISP, *this);
508 // Get call node, we will replace it later with statepoint
509 SDNode *CallNode = lowerCallFromStatepoint(CI, *this);
511 // Construct the actual STATEPOINT node with all the appropriate arguments
512 // and return values.
514 // TODO: Currently, all of these operands are being marked as read/write in
515 // PrologEpilougeInserter.cpp, we should special case the VMState arguments
516 // and flags to be read-only.
517 SmallVector<SDValue, 40> Ops;
519 // Calculate and push starting position of vmstate arguments
520 // Call Node: Chain, Target, {Args}, RegMask, [Glue]
522 if (CallNode->getGluedNode()) {
523 // Glue is always last operand
524 Glue = CallNode->getOperand(CallNode->getNumOperands() - 1);
526 // Get number of arguments incoming directly into call node
527 unsigned NumCallRegArgs =
528 CallNode->getNumOperands() - (Glue.getNode() ? 4 : 3);
529 Ops.push_back(DAG.getTargetConstant(NumCallRegArgs, MVT::i32));
532 SDValue CallTarget = SDValue(CallNode->getOperand(1).getNode(), 0);
533 Ops.push_back(CallTarget);
535 // Add call arguments
536 // Get position of register mask in the call
537 SDNode::op_iterator RegMaskIt;
539 RegMaskIt = CallNode->op_end() - 2;
541 RegMaskIt = CallNode->op_end() - 1;
542 Ops.insert(Ops.end(), CallNode->op_begin() + 2, RegMaskIt);
544 // Add a leading constant argument with the Flags and the calling convention
546 CallingConv::ID CallConv = CI.getCallingConv();
547 int Flags = dyn_cast<ConstantInt>(CI.getArgOperand(2))->getZExtValue();
548 assert(Flags == 0 && "not expected to be used");
549 Ops.push_back(DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
551 DAG.getTargetConstant(Flags | ((unsigned)CallConv << 1), MVT::i64));
553 // Insert all vmstate and gcstate arguments
554 Ops.insert(Ops.end(), LoweredArgs.begin(), LoweredArgs.end());
556 // Add register mask from call node
557 Ops.push_back(*RegMaskIt);
560 Ops.push_back(CallNode->getOperand(0));
562 // Same for the glue, but we add it only if original call had it
566 // Compute return values
567 SmallVector<EVT, 21> ValueVTs;
568 ValueVTs.push_back(MVT::Other);
569 ValueVTs.push_back(MVT::Glue); // provide a glue output since we consume one
570 // as input. This allows someone else to chain
572 SDVTList NodeTys = DAG.getVTList(ValueVTs);
574 SDNode *StatepointMCNode = DAG.getMachineNode(TargetOpcode::STATEPOINT,
575 getCurSDLoc(), NodeTys, Ops);
577 // Replace original call
578 DAG.ReplaceAllUsesWith(CallNode, StatepointMCNode); // This may update Root
579 // Remove originall call node
580 DAG.DeleteNode(CallNode);
582 // DON'T set the root - under the assumption that it's already set past the
583 // inserted node we created.
585 // TODO: A better future implementation would be to emit a single variable
586 // argument, variable return value STATEPOINT node here and then hookup the
587 // return value of each gc.relocate to the respective output of the
588 // previously emitted STATEPOINT value. Unfortunately, this doesn't appear
589 // to actually be possible today.
592 void SelectionDAGBuilder::visitGCResult(const CallInst &CI) {
593 // The result value of the gc_result is simply the result of the actual
594 // call. We've already emitted this, so just grab the value.
595 Instruction *I = cast<Instruction>(CI.getArgOperand(0));
596 assert(isStatepoint(I) &&
597 "first argument must be a statepoint token");
599 setValue(&CI, getValue(I));
602 void SelectionDAGBuilder::visitGCRelocate(const CallInst &CI) {
605 StatepointLowering.relocCallVisited(CI);
608 GCRelocateOperands relocateOpers(&CI);
609 SDValue SD = getValue(relocateOpers.derivedPtr());
611 if (isa<ConstantSDNode>(SD) || isa<FrameIndexSDNode>(SD)) {
612 // We didn't need to spill these special cases (constants and allocas).
613 // See the handling in spillIncomingValueForStatepoint for detail.
618 SDValue Loc = StatepointLowering.getRelocLocation(SD);
619 // Emit new load if we did not emit it before
620 if (!Loc.getNode()) {
621 SDValue SpillSlot = StatepointLowering.getLocation(SD);
622 int FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
624 // Be conservative: flush all pending loads
625 // TODO: Probably we can be less restrictive on this,
626 // it may allow more scheduling opprtunities
627 SDValue Chain = getRoot();
629 Loc = DAG.getLoad(SpillSlot.getValueType(), getCurSDLoc(), Chain,
630 SpillSlot, MachinePointerInfo::getFixedStack(FI), false,
633 StatepointLowering.setRelocLocation(SD, Loc);
635 // Again, be conservative, don't emit pending loads
636 DAG.setRoot(Loc.getValue(1));
639 assert(Loc.getNode());