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Extend the statepoint intrinsic to allow statepoints to be marked as transitions from GC-aware code to code that is not GC-aware.

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This changes the shape of the statepoint intrinsic from:

  @llvm.experimental.gc.statepoint(anyptr target, i32 # call args, i32 unused, ...call args, i32 # deopt args, ...deopt args, ...gc args)

to:

  @llvm.experimental.gc.statepoint(anyptr target, i32 # call args, i32 flags, ...call args, i32 # transition args, ...transition args, i32 # deopt args, ...deopt args, ...gc args)

This extension offers the backend the opportunity to insert (somewhat) arbitrary code to manage the transition from GC-aware code to code that is not GC-aware and back.

In order to support the injection of transition code, this extension wraps the STATEPOINT ISD node generated by the usual lowering lowering with two additional nodes: GC_TRANSITION_START and GC_TRANSITION_END. The transition arguments that were passed passed to the intrinsic (if any) are lowered and provided as operands to these nodes and may be used by the backend during code generation.

Eventually, the lowering of the GC_TRANSITION_{START,END} nodes should be informed by the GC strategy in use for the function containing the intrinsic call; for now, these nodes are instead replaced with no-ops.

Differential Revision: http://reviews.llvm.org/D9501

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236888 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Pat Gavlin
2015-05-08 18:07:42 +00:00
parent c417f302cb
commit 5c7f7462e4
43 changed files with 616 additions and 180 deletions
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102
lib/CodeGen/SelectionDAG/StatepointLowering.cpp
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@@ -585,24 +585,66 @@ void SelectionDAGBuilder::LowerStatepoint(
SDNode *CallNode =
lowerCallFromStatepoint(ISP, LandingPad, *this, PendingExports);
// Construct the actual STATEPOINT node with all the appropriate arguments
// and return values.
// Construct the actual GC_TRANSITION_START, STATEPOINT, and GC_TRANSITION_END
// nodes 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 Chain = CallNode->getOperand(0);
SDValue Glue;
if (CallNode->getGluedNode()) {
bool CallHasIncomingGlue = CallNode->getGluedNode();
if (CallHasIncomingGlue) {
// Glue is always last operand
Glue = CallNode->getOperand(CallNode->getNumOperands() - 1);
}
// Build the GC_TRANSITION_START node if necessary.
//
// The operands to the GC_TRANSITION_{START,END} nodes are laid out in the
// order in which they appear in the call to the statepoint intrinsic. If
// any of the operands is a pointer-typed, that operand is immediately
// followed by a SRCVALUE for the pointer that may be used during lowering
// (e.g. to form MachinePointerInfo values for loads/stores).
const bool IsGCTransition =
(ISP.getFlags() & (uint64_t)StatepointFlags::GCTransition) ==
(uint64_t)StatepointFlags::GCTransition;
if (IsGCTransition) {
SmallVector<SDValue, 8> TSOps;
// Add chain
TSOps.push_back(Chain);
// Add GC transition arguments
for (auto I = ISP.gc_transition_args_begin() + 1,
E = ISP.gc_transition_args_end();
I != E; ++I) {
TSOps.push_back(getValue(*I));
if ((*I)->getType()->isPointerTy())
TSOps.push_back(DAG.getSrcValue(*I));
}
// Add glue if necessary
if (CallHasIncomingGlue)
TSOps.push_back(Glue);
SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
SDValue GCTransitionStart =
DAG.getNode(ISD::GC_TRANSITION_START, getCurSDLoc(), NodeTys, TSOps);
Chain = GCTransitionStart.getValue(0);
Glue = GCTransitionStart.getValue(1);
}
// Calculate and push starting position of vmstate arguments
// Get number of arguments incoming directly into call node
unsigned NumCallRegArgs =
CallNode->getNumOperands() - (Glue.getNode() ? 4 : 3);
CallNode->getNumOperands() - (CallHasIncomingGlue ? 4 : 3);
Ops.push_back(DAG.getTargetConstant(NumCallRegArgs, getCurSDLoc(), MVT::i32));
// Add call target
@@ -612,7 +654,7 @@ void SelectionDAGBuilder::LowerStatepoint(
// Add call arguments
// Get position of register mask in the call
SDNode::op_iterator RegMaskIt;
if (Glue.getNode())
if (CallHasIncomingGlue)
RegMaskIt = CallNode->op_end() - 2;
else
RegMaskIt = CallNode->op_end() - 1;
@@ -621,11 +663,17 @@ void SelectionDAGBuilder::LowerStatepoint(
// Add a leading constant argument with the Flags and the calling convention
// masked together
CallingConv::ID CallConv = CS.getCallingConv();
int Flags = cast<ConstantInt>(CS.getArgument(2))->getZExtValue();
assert(Flags == 0 && "not expected to be used");
uint64_t Flags = cast<ConstantInt>(CS.getArgument(2))->getZExtValue();
assert(
((Flags & ~(uint64_t)StatepointFlags::MaskAll) == 0)
&& "unknown flag used");
const int Shift = 1;
static_assert(
((~(uint64_t)0 << Shift) & (uint64_t)StatepointFlags::MaskAll) == 0,
"shift width too small");
Ops.push_back(DAG.getTargetConstant(StackMaps::ConstantOp, getCurSDLoc(),
MVT::i64));
Ops.push_back(DAG.getTargetConstant(Flags | ((unsigned)CallConv << 1),
Ops.push_back(DAG.getTargetConstant(Flags | ((unsigned)CallConv << Shift),
getCurSDLoc(), MVT::i64));
// Insert all vmstate and gcstate arguments
@@ -635,7 +683,7 @@ void SelectionDAGBuilder::LowerStatepoint(
Ops.push_back(*RegMaskIt);
// Add chain
Ops.push_back(CallNode->getOperand(0));
Ops.push_back(Chain);
// Same for the glue, but we add it only if original call had it
if (Glue.getNode())
@@ -648,8 +696,40 @@ void SelectionDAGBuilder::LowerStatepoint(
SDNode *StatepointMCNode =
DAG.getMachineNode(TargetOpcode::STATEPOINT, getCurSDLoc(), NodeTys, Ops);
SDNode *SinkNode = StatepointMCNode;
// Build the GC_TRANSITION_END node if necessary.
//
// See the comment above regarding GC_TRANSITION_START for the layout of
// the operands to the GC_TRANSITION_END node.
if (IsGCTransition) {
SmallVector<SDValue, 8> TEOps;
// Add chain
TEOps.push_back(SDValue(StatepointMCNode, 0));
// Add GC transition arguments
for (auto I = ISP.gc_transition_args_begin() + 1,
E = ISP.gc_transition_args_end();
I != E; ++I) {
TEOps.push_back(getValue(*I));
if ((*I)->getType()->isPointerTy())
TEOps.push_back(DAG.getSrcValue(*I));
}
// Add glue
TEOps.push_back(SDValue(StatepointMCNode, 1));
SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
SDValue GCTransitionStart =
DAG.getNode(ISD::GC_TRANSITION_END, getCurSDLoc(), NodeTys, TEOps);
SinkNode = GCTransitionStart.getNode();
}
// Replace original call
DAG.ReplaceAllUsesWith(CallNode, StatepointMCNode); // This may update Root
DAG.ReplaceAllUsesWith(CallNode, SinkNode); // This may update Root
// Remove originall call node
DAG.DeleteNode(CallNode);