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llvm-6502/lib/CodeGen/SelectionDAG/StatepointLowering.cpp

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//===-- StatepointLowering.cpp - SDAGBuilder's statepoint code -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file includes support code use by SelectionDAGBuilder when lowering a
// statepoint sequence in SelectionDAG IR.
//
//===----------------------------------------------------------------------===//
#include "StatepointLowering.h"
#include "SelectionDAGBuilder.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/GCMetadata.h"
#include "llvm/CodeGen/GCStrategy.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Statepoint.h"
#include "llvm/Target/TargetLowering.h"
#include <algorithm>
using namespace llvm;
#define DEBUG_TYPE "statepoint-lowering"
STATISTIC(NumSlotsAllocatedForStatepoints,
"Number of stack slots allocated for statepoints");
STATISTIC(NumOfStatepoints, "Number of statepoint nodes encountered");
STATISTIC(StatepointMaxSlotsRequired,
"Maximum number of stack slots required for a singe statepoint");
void
StatepointLoweringState::startNewStatepoint(SelectionDAGBuilder &Builder) {
// Consistency check
assert(PendingGCRelocateCalls.empty() &&
"Trying to visit statepoint before finished processing previous one");
Locations.clear();
RelocLocations.clear();
NextSlotToAllocate = 0;
// Need to resize this on each safepoint - we need the two to stay in
// sync and the clear patterns of a SelectionDAGBuilder have no relation
// to FunctionLoweringInfo.
AllocatedStackSlots.resize(Builder.FuncInfo.StatepointStackSlots.size());
for (size_t i = 0; i < AllocatedStackSlots.size(); i++) {
AllocatedStackSlots[i] = false;
}
}
void StatepointLoweringState::clear() {
Locations.clear();
RelocLocations.clear();
AllocatedStackSlots.clear();
assert(PendingGCRelocateCalls.empty() &&
"cleared before statepoint sequence completed");
}
SDValue
StatepointLoweringState::allocateStackSlot(EVT ValueType,
SelectionDAGBuilder &Builder) {
NumSlotsAllocatedForStatepoints++;
// The basic scheme here is to first look for a previously created stack slot
// which is not in use (accounting for the fact arbitrary slots may already
// be reserved), or to create a new stack slot and use it.
// If this doesn't succeed in 40000 iterations, something is seriously wrong
for (int i = 0; i < 40000; i++) {
assert(Builder.FuncInfo.StatepointStackSlots.size() ==
AllocatedStackSlots.size() &&
"broken invariant");
const size_t NumSlots = AllocatedStackSlots.size();
assert(NextSlotToAllocate <= NumSlots && "broken invariant");
if (NextSlotToAllocate >= NumSlots) {
assert(NextSlotToAllocate == NumSlots);
// record stats
if (NumSlots + 1 > StatepointMaxSlotsRequired) {
StatepointMaxSlotsRequired = NumSlots + 1;
}
SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType);
const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
Builder.FuncInfo.StatepointStackSlots.push_back(FI);
AllocatedStackSlots.push_back(true);
return SpillSlot;
}
if (!AllocatedStackSlots[NextSlotToAllocate]) {
const int FI = Builder.FuncInfo.StatepointStackSlots[NextSlotToAllocate];
AllocatedStackSlots[NextSlotToAllocate] = true;
return Builder.DAG.getFrameIndex(FI, ValueType);
}
// Note: We deliberately choose to advance this only on the failing path.
// Doing so on the suceeding path involes a bit of complexity that caused a
// minor bug previously. Unless performance shows this matters, please
// keep this code as simple as possible.
NextSlotToAllocate++;
}
llvm_unreachable("infinite loop?");
}
/// Try to find existing copies of the incoming values in stack slots used for
/// statepoint spilling. If we can find a spill slot for the incoming value,
/// mark that slot as allocated, and reuse the same slot for this safepoint.
/// This helps to avoid series of loads and stores that only serve to resuffle
/// values on the stack between calls.
static void reservePreviousStackSlotForValue(SDValue Incoming,
SelectionDAGBuilder &Builder) {
if (isa<ConstantSDNode>(Incoming) || isa<FrameIndexSDNode>(Incoming)) {
// We won't need to spill this, so no need to check for previously
// allocated stack slots
return;
}
SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);
if (Loc.getNode()) {
// duplicates in input
return;
}
// Search back for the load from a stack slot pattern to find the original
// slot we allocated for this value. We could extend this to deal with
// simple modification patterns, but simple dealing with trivial load/store
// sequences helps a lot already.
if (LoadSDNode *Load = dyn_cast<LoadSDNode>(Incoming)) {
if (auto *FI = dyn_cast<FrameIndexSDNode>(Load->getBasePtr())) {
const int Index = FI->getIndex();
auto Itr = std::find(Builder.FuncInfo.StatepointStackSlots.begin(),
Builder.FuncInfo.StatepointStackSlots.end(), Index);
if (Itr == Builder.FuncInfo.StatepointStackSlots.end()) {
// not one of the lowering stack slots, can't reuse!
// TODO: Actually, we probably could reuse the stack slot if the value
// hasn't changed at all, but we'd need to look for intervening writes
return;
} else {
// This is one of our dedicated lowering slots
const int Offset =
std::distance(Builder.FuncInfo.StatepointStackSlots.begin(), Itr);
if (Builder.StatepointLowering.isStackSlotAllocated(Offset)) {
// stack slot already assigned to someone else, can't use it!
// TODO: currently we reserve space for gc arguments after doing
// normal allocation for deopt arguments. We should reserve for
// _all_ deopt and gc arguments, then start allocating. This
// will prevent some moves being inserted when vm state changes,
// but gc state doesn't between two calls.
return;
}
// Reserve this stack slot
Builder.StatepointLowering.reserveStackSlot(Offset);
}
// Cache this slot so we find it when going through the normal
// assignment loop.
SDValue Loc =
Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType());
Builder.StatepointLowering.setLocation(Incoming, Loc);
}
}
// TODO: handle case where a reloaded value flows through a phi to
// another safepoint. e.g.
// bb1:
// a' = relocated...
// bb2: % pred: bb1, bb3, bb4, etc.
// a_phi = phi(a', ...)
// statepoint ... a_phi
// NOTE: This will require reasoning about cross basic block values. This is
// decidedly non trivial and this might not be the right place to do it. We
// don't really have the information we need here...
// TODO: handle simple updates. If a value is modified and the original
// value is no longer live, it would be nice to put the modified value in the
// same slot. This allows folding of the memory accesses for some
// instructions types (like an increment).
// statepoint (i)
// i1 = i+1
// statepoint (i1)
}
/// Remove any duplicate (as SDValues) from the derived pointer pairs. This
/// is not required for correctness. It's purpose is to reduce the size of
/// StackMap section. It has no effect on the number of spill slots required
/// or the actual lowering.
static void removeDuplicatesGCPtrs(SmallVectorImpl<const Value *> &Bases,
SmallVectorImpl<const Value *> &Ptrs,
SmallVectorImpl<const Value *> &Relocs,
SelectionDAGBuilder &Builder) {
// This is horribly ineffecient, but I don't care right now
SmallSet<SDValue, 64> Seen;
SmallVector<const Value *, 64> NewBases, NewPtrs, NewRelocs;
for (size_t i = 0; i < Ptrs.size(); i++) {
SDValue SD = Builder.getValue(Ptrs[i]);
// Only add non-duplicates
if (Seen.count(SD) == 0) {
NewBases.push_back(Bases[i]);
NewPtrs.push_back(Ptrs[i]);
NewRelocs.push_back(Relocs[i]);
}
Seen.insert(SD);
}
assert(Bases.size() >= NewBases.size());
assert(Ptrs.size() >= NewPtrs.size());
assert(Relocs.size() >= NewRelocs.size());
Bases = NewBases;
Ptrs = NewPtrs;
Relocs = NewRelocs;
assert(Ptrs.size() == Bases.size());
assert(Ptrs.size() == Relocs.size());
}
/// Extract call from statepoint, lower it and return pointer to the
/// call node. Also update NodeMap so that getValue(statepoint) will
/// reference lowered call result
static SDNode *lowerCallFromStatepoint(ImmutableStatepoint StatepointSite,
SelectionDAGBuilder &Builder) {
ImmutableCallSite CS(StatepointSite.getCallSite());
// Lower the actual call itself - This is a bit of a hack, but we want to
// avoid modifying the actual lowering code. This is similiar in intent to
// the LowerCallOperands mechanism used by PATCHPOINT, but is structured
// differently. Hopefully, this is slightly more robust w.r.t. calling
// convention, return values, and other function attributes.
Value *ActualCallee = const_cast<Value *>(StatepointSite.actualCallee());
std::vector<Value *> Args;
CallInst::const_op_iterator arg_begin = StatepointSite.call_args_begin();
CallInst::const_op_iterator arg_end = StatepointSite.call_args_end();
Args.insert(Args.end(), arg_begin, arg_end);
// TODO: remove the creation of a new instruction! We should not be
// modifying the IR (even temporarily) at this point.
CallInst *Tmp = CallInst::Create(ActualCallee, Args);
Tmp->setTailCall(CS.isTailCall());
Tmp->setCallingConv(CS.getCallingConv());
Tmp->setAttributes(CS.getAttributes());
Builder.LowerCallTo(Tmp, Builder.getValue(ActualCallee), false);
// Handle the return value of the call iff any.
const bool HasDef = !Tmp->getType()->isVoidTy();
if (HasDef) {
// The value of the statepoint itself will be the value of call itself.
// We'll replace the actually call node shortly. gc_result will grab
// this value.
Builder.setValue(CS.getInstruction(), Builder.getValue(Tmp));
} else {
// The token value is never used from here on, just generate a poison value
Builder.setValue(CS.getInstruction(), Builder.DAG.getIntPtrConstant(-1));
}
// Remove the fake entry we created so we don't have a hanging reference
// after we delete this node.
Builder.removeValue(Tmp);
delete Tmp;
Tmp = nullptr;
// Search for the call node
// The following code is essentially reverse engineering X86's
// LowerCallTo.
SDNode *CallNode = nullptr;
// We just emitted a call, so it should be last thing generated
SDValue Chain = Builder.DAG.getRoot();
// Find closest CALLSEQ_END walking back through lowered nodes if needed
SDNode *CallEnd = Chain.getNode();
int Sanity = 0;
while (CallEnd->getOpcode() != ISD::CALLSEQ_END) {
CallEnd = CallEnd->getGluedNode();
assert(CallEnd && "Can not find call node");
assert(Sanity < 20 && "should have found call end already");
Sanity++;
}
assert(CallEnd->getOpcode() == ISD::CALLSEQ_END &&
"Expected a callseq node.");
assert(CallEnd->getGluedNode());
// Step back inside the CALLSEQ
CallNode = CallEnd->getGluedNode();
return CallNode;
}
/// Callect all gc pointers coming into statepoint intrinsic, clean them up,
/// and return two arrays:
/// Bases - base pointers incoming to this statepoint
/// Ptrs - derived pointers incoming to this statepoint
/// Relocs - the gc_relocate corresponding to each base/ptr pair
/// Elements of this arrays should be in one-to-one correspondence with each
/// other i.e Bases[i], Ptrs[i] are from the same gcrelocate call
static void
getIncomingStatepointGCValues(SmallVectorImpl<const Value *> &Bases,
SmallVectorImpl<const Value *> &Ptrs,
SmallVectorImpl<const Value *> &Relocs,
ImmutableStatepoint StatepointSite,
SelectionDAGBuilder &Builder) {
for (GCRelocateOperands relocateOpers :
StatepointSite.getRelocates(StatepointSite)) {
Relocs.push_back(relocateOpers.getUnderlyingCallSite().getInstruction());
Bases.push_back(relocateOpers.basePtr());
Ptrs.push_back(relocateOpers.derivedPtr());
}
// Remove any redundant llvm::Values which map to the same SDValue as another
// input. Also has the effect of removing duplicates in the original
// llvm::Value input list as well. This is a useful optimization for
// reducing the size of the StackMap section. It has no other impact.
removeDuplicatesGCPtrs(Bases, Ptrs, Relocs, Builder);
assert(Bases.size() == Ptrs.size() && Ptrs.size() == Relocs.size());
}
/// Spill a value incoming to the statepoint. It might be either part of
/// vmstate
/// or gcstate. In both cases unconditionally spill it on the stack unless it
/// is a null constant. Return pair with first element being frame index
/// containing saved value and second element with outgoing chain from the
/// emitted store
static std::pair<SDValue, SDValue>
spillIncomingStatepointValue(SDValue Incoming, SDValue Chain,
SelectionDAGBuilder &Builder) {
SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);
// Emit new store if we didn't do it for this ptr before
if (!Loc.getNode()) {
Loc = Builder.StatepointLowering.allocateStackSlot(Incoming.getValueType(),
Builder);
assert(isa<FrameIndexSDNode>(Loc));
int Index = cast<FrameIndexSDNode>(Loc)->getIndex();
// We use TargetFrameIndex so that isel will not select it into LEA
Loc = Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType());
// TODO: We can create TokenFactor node instead of
// chaining stores one after another, this may allow
// a bit more optimal scheduling for them
Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc,
MachinePointerInfo::getFixedStack(Index),
false, false, 0);
Builder.StatepointLowering.setLocation(Incoming, Loc);
}
assert(Loc.getNode());
return std::make_pair(Loc, Chain);
}
/// Lower a single value incoming to a statepoint node. This value can be
/// either a deopt value or a gc value, the handling is the same. We special
/// case constants and allocas, then fall back to spilling if required.
static void lowerIncomingStatepointValue(SDValue Incoming,
SmallVectorImpl<SDValue> &Ops,
SelectionDAGBuilder &Builder) {
SDValue Chain = Builder.getRoot();
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) {
// If the original value was a constant, make sure it gets recorded as
// such in the stackmap. This is required so that the consumer can
// parse any internal format to the deopt state. It also handles null
// pointers and other constant pointers in GC states
Ops.push_back(
Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
Ops.push_back(Builder.DAG.getTargetConstant(C->getSExtValue(), MVT::i64));
} else if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) {
// This handles allocas as arguments to the statepoint
const TargetLowering &TLI = Builder.DAG.getTargetLoweringInfo();
Ops.push_back(
Builder.DAG.getTargetFrameIndex(FI->getIndex(), TLI.getPointerTy()));
} else {
// Otherwise, locate a spill slot and explicitly spill it so it
// can be found by the runtime later. We currently do not support
// tracking values through callee saved registers to their eventual
// spill location. This would be a useful optimization, but would
// need to be optional since it requires a lot of complexity on the
// runtime side which not all would support.
std::pair<SDValue, SDValue> Res =
spillIncomingStatepointValue(Incoming, Chain, Builder);
Ops.push_back(Res.first);
Chain = Res.second;
}
Builder.DAG.setRoot(Chain);
}
/// Lower deopt state and gc pointer arguments of the statepoint. The actual
/// lowering is described in lowerIncomingStatepointValue. This function is
/// responsible for lowering everything in the right position and playing some
/// tricks to avoid redundant stack manipulation where possible. On
/// completion, 'Ops' will contain ready to use operands for machine code
/// statepoint. The chain nodes will have already been created and the DAG root
/// will be set to the last value spilled (if any were).
static void lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops,
ImmutableStatepoint StatepointSite,
SelectionDAGBuilder &Builder) {
// Lower the deopt and gc arguments for this statepoint. Layout will
// be: deopt argument length, deopt arguments.., gc arguments...
SmallVector<const Value *, 64> Bases, Ptrs, Relocations;
getIncomingStatepointGCValues(Bases, Ptrs, Relocations,
StatepointSite, Builder);
#ifndef NDEBUG
// Check that each of the gc pointer and bases we've gotten out of the
// safepoint is something the strategy thinks might be a pointer into the GC
// heap. This is basically just here to help catch errors during statepoint
// insertion. TODO: This should actually be in the Verifier, but we can't get
// to the GCStrategy from there (yet).
if (Builder.GFI) {
GCStrategy &S = Builder.GFI->getStrategy();
for (const Value *V : Bases) {
auto Opt = S.isGCManagedPointer(V);
if (Opt.hasValue()) {
assert(Opt.getValue() &&
"non gc managed base pointer found in statepoint");
}
}
for (const Value *V : Ptrs) {
auto Opt = S.isGCManagedPointer(V);
if (Opt.hasValue()) {
assert(Opt.getValue() &&
"non gc managed derived pointer found in statepoint");
}
}
for (const Value *V : Relocations) {
auto Opt = S.isGCManagedPointer(V);
if (Opt.hasValue()) {
assert(Opt.getValue() && "non gc managed pointer relocated");
}
}
}
#endif
// Before we actually start lowering (and allocating spill slots for values),
// reserve any stack slots which we judge to be profitable to reuse for a
// particular value. This is purely an optimization over the code below and
// doesn't change semantics at all. It is important for performance that we
// reserve slots for both deopt and gc values before lowering either.
for (auto I = StatepointSite.vm_state_begin() + 1,
E = StatepointSite.vm_state_end();
I != E; ++I) {
Value *V = *I;
SDValue Incoming = Builder.getValue(V);
reservePreviousStackSlotForValue(Incoming, Builder);
}
for (unsigned i = 0; i < Bases.size() * 2; ++i) {
// Even elements will contain base, odd elements - derived ptr
const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2];
SDValue Incoming = Builder.getValue(V);
reservePreviousStackSlotForValue(Incoming, Builder);
}
// First, prefix the list with the number of unique values to be
// lowered. Note that this is the number of *Values* not the
// number of SDValues required to lower them.
const int NumVMSArgs = StatepointSite.numTotalVMSArgs();
Ops.push_back(
Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
Ops.push_back(Builder.DAG.getTargetConstant(NumVMSArgs, MVT::i64));
assert(NumVMSArgs + 1 == std::distance(StatepointSite.vm_state_begin(),
StatepointSite.vm_state_end()));
// The vm state arguments are lowered in an opaque manner. We do
// not know what type of values are contained within. We skip the
// first one since that happens to be the total number we lowered
// explicitly just above. We could have left it in the loop and
// not done it explicitly, but it's far easier to understand this
// way.
for (auto I = StatepointSite.vm_state_begin() + 1,
E = StatepointSite.vm_state_end();
I != E; ++I) {
const Value *V = *I;
SDValue Incoming = Builder.getValue(V);
lowerIncomingStatepointValue(Incoming, Ops, Builder);
}
// Finally, go ahead and lower all the gc arguments. There's no prefixed
// length for this one. After lowering, we'll have the base and pointer
// arrays interwoven with each (lowered) base pointer immediately followed by
// it's (lowered) derived pointer. i.e
// (base[0], ptr[0], base[1], ptr[1], ...)
for (unsigned i = 0; i < Bases.size() * 2; ++i) {
// Even elements will contain base, odd elements - derived ptr
const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2];
SDValue Incoming = Builder.getValue(V);
lowerIncomingStatepointValue(Incoming, Ops, Builder);
}
}
void SelectionDAGBuilder::visitStatepoint(const CallInst &CI) {
// Check some preconditions for sanity
assert(isStatepoint(&CI) &&
"function called must be the statepoint function");
LowerStatepoint(ImmutableStatepoint(&CI));
}
void SelectionDAGBuilder::LowerStatepoint(ImmutableStatepoint ISP) {
// The basic scheme here is that information about both the original call and
// the safepoint is encoded in the CallInst. We create a temporary call and
// lower it, then reverse engineer the calling sequence.
NumOfStatepoints++;
// Clear state
StatepointLowering.startNewStatepoint(*this);
ImmutableCallSite CS(ISP.getCallSite());
#ifndef NDEBUG
// Consistency check
for (const User *U : CS->users()) {
const CallInst *Call = cast<CallInst>(U);
if (isGCRelocate(Call))
StatepointLowering.scheduleRelocCall(*Call);
}
#endif
#ifndef NDEBUG
// If this is a malformed statepoint, report it early to simplify debugging.
// This should catch any IR level mistake that's made when constructing or
// transforming statepoints.
ISP.verify();
// Check that the associated GCStrategy expects to encounter statepoints.
// TODO: This if should become an assert. For now, we allow the GCStrategy
// to be optional for backwards compatibility. This will only last a short
// period (i.e. a couple of weeks).
if (GFI) {
assert(GFI->getStrategy().useStatepoints() &&
"GCStrategy does not expect to encounter statepoints");
}
#endif
// Lower statepoint vmstate and gcstate arguments
SmallVector<SDValue, 10> LoweredArgs;
lowerStatepointMetaArgs(LoweredArgs, ISP, *this);
// Get call node, we will replace it later with statepoint
SDNode *CallNode = lowerCallFromStatepoint(ISP, *this);
// Construct the actual STATEPOINT node with all the appropriate arguments
// and return values.
// TODO: Currently, all of these operands are being marked as read/write in
// PrologEpilougeInserter.cpp, we should special case the VMState arguments
// and flags to be read-only.
SmallVector<SDValue, 40> Ops;
// Calculate and push starting position of vmstate arguments
// Call Node: Chain, Target, {Args}, RegMask, [Glue]
SDValue Glue;
if (CallNode->getGluedNode()) {
// Glue is always last operand
Glue = CallNode->getOperand(CallNode->getNumOperands() - 1);
}
// Get number of arguments incoming directly into call node
unsigned NumCallRegArgs =
CallNode->getNumOperands() - (Glue.getNode() ? 4 : 3);
Ops.push_back(DAG.getTargetConstant(NumCallRegArgs, MVT::i32));
// Add call target
SDValue CallTarget = SDValue(CallNode->getOperand(1).getNode(), 0);
Ops.push_back(CallTarget);
// Add call arguments
// Get position of register mask in the call
SDNode::op_iterator RegMaskIt;
if (Glue.getNode())
RegMaskIt = CallNode->op_end() - 2;
else
RegMaskIt = CallNode->op_end() - 1;
Ops.insert(Ops.end(), CallNode->op_begin() + 2, RegMaskIt);
// Add a leading constant argument with the Flags and the calling convention
// masked together
CallingConv::ID CallConv = CS.getCallingConv();
int Flags = dyn_cast<ConstantInt>(CS.getArgument(2))->getZExtValue();
assert(Flags == 0 && "not expected to be used");
Ops.push_back(DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64));
Ops.push_back(
DAG.getTargetConstant(Flags | ((unsigned)CallConv << 1), MVT::i64));
// Insert all vmstate and gcstate arguments
Ops.insert(Ops.end(), LoweredArgs.begin(), LoweredArgs.end());
// Add register mask from call node
Ops.push_back(*RegMaskIt);
// Add chain
Ops.push_back(CallNode->getOperand(0));
// Same for the glue, but we add it only if original call had it
if (Glue.getNode())
Ops.push_back(Glue);
// Compute return values. Provide a glue output since we consume one as
// input. This allows someone else to chain off us as needed.
SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
SDNode *StatepointMCNode = DAG.getMachineNode(TargetOpcode::STATEPOINT,
getCurSDLoc(), NodeTys, Ops);
// Replace original call
DAG.ReplaceAllUsesWith(CallNode, StatepointMCNode); // This may update Root
// Remove originall call node
DAG.DeleteNode(CallNode);
// DON'T set the root - under the assumption that it's already set past the
// inserted node we created.
// TODO: A better future implementation would be to emit a single variable
// argument, variable return value STATEPOINT node here and then hookup the
// return value of each gc.relocate to the respective output of the
// previously emitted STATEPOINT value. Unfortunately, this doesn't appear
// to actually be possible today.
}
void SelectionDAGBuilder::visitGCResult(const CallInst &CI) {
// The result value of the gc_result is simply the result of the actual
// call. We've already emitted this, so just grab the value.
Instruction *I = cast<Instruction>(CI.getArgOperand(0));
assert(isStatepoint(I) &&
"first argument must be a statepoint token");
setValue(&CI, getValue(I));
}
void SelectionDAGBuilder::visitGCRelocate(const CallInst &CI) {
#ifndef NDEBUG
// Consistency check
StatepointLowering.relocCallVisited(CI);
#endif
GCRelocateOperands relocateOpers(&CI);
SDValue SD = getValue(relocateOpers.derivedPtr());
if (isa<ConstantSDNode>(SD) || isa<FrameIndexSDNode>(SD)) {
// We didn't need to spill these special cases (constants and allocas).
// See the handling in spillIncomingValueForStatepoint for detail.
setValue(&CI, SD);
return;
}
SDValue Loc = StatepointLowering.getRelocLocation(SD);
// Emit new load if we did not emit it before
if (!Loc.getNode()) {
SDValue SpillSlot = StatepointLowering.getLocation(SD);
int FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
// Be conservative: flush all pending loads
// TODO: Probably we can be less restrictive on this,
// it may allow more scheduling opprtunities
SDValue Chain = getRoot();
Loc = DAG.getLoad(SpillSlot.getValueType(), getCurSDLoc(), Chain,
SpillSlot, MachinePointerInfo::getFixedStack(FI), false,
false, false, 0);
StatepointLowering.setRelocLocation(SD, Loc);
// Again, be conservative, don't emit pending loads
DAG.setRoot(Loc.getValue(1));
}
assert(Loc.getNode());
setValue(&CI, Loc);
}
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