[SDAG] Remove the reliance on MI's allocation strategy for
`MachineMemOperand` pointers attached to `MachineSDNodes` and instead
have the `SelectionDAG` fully manage the memory for this array.
Prior to this change, the memory management was deeply confusing here --
The way the MI was built relied on the `SelectionDAG` allocating memory
for these arrays of pointers using the `MachineFunction`'s allocator so
that the raw pointer to the array could be blindly copied into an
eventual `MachineInstr`. This creates a hard coupling between how
`MachineInstr`s allocate their array of `MachineMemOperand` pointers and
how the `MachineSDNode` does.
This change is motivated in large part by a change I am making to how
`MachineFunction` allocates these pointers, but it seems like a layering
improvement as well.
This would run the risk of increasing allocations overall, but I've
implemented an optimization that should avoid that by storing a single
`MachineMemOperand` pointer directly instead of allocating anything.
This is expected to be a net win because the vast majority of uses of
these only need a single pointer.
As a side-effect, this makes the API for updating a `MachineSDNode` and
a `MachineInstr` reasonably different which seems nice to avoid
unexpected coupling of these two layers. We can map between them, but we
shouldn't be *surprised* at where that occurs. =]
Differential Revision: https://reviews.llvm.org/D50680
llvm-svn: 339740
diff --git a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
index 6cec664..54239c2 100644
--- a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
@@ -4045,9 +4045,8 @@
void PPCDAGToDAGISel::transferMemOperands(SDNode *N, SDNode *Result) {
// Transfer memoperands.
- MachineSDNode::mmo_iterator MemOp = MF->allocateMemRefsArray(1);
- MemOp[0] = cast<MemSDNode>(N)->getMemOperand();
- cast<MachineSDNode>(Result)->setMemRefs(MemOp, MemOp + 1);
+ MachineMemOperand *MemOp = cast<MemSDNode>(N)->getMemOperand();
+ CurDAG->setNodeMemRefs(cast<MachineSDNode>(Result), {MemOp});
}
/// This method returns a node after flipping the MSB of each element
@@ -4683,11 +4682,10 @@
SelectAddrIdxOnly(LD->getBasePtr(), Base, Offset)) {
SDValue Chain = LD->getChain();
SDValue Ops[] = { Base, Offset, Chain };
- MachineSDNode::mmo_iterator MemOp = MF->allocateMemRefsArray(1);
- MemOp[0] = LD->getMemOperand();
+ MachineMemOperand *MemOp = LD->getMemOperand();
SDNode *NewN = CurDAG->SelectNodeTo(N, PPC::LXVDSX,
N->getValueType(0), Ops);
- cast<MachineSDNode>(NewN)->setMemRefs(MemOp, MemOp + 1);
+ CurDAG->setNodeMemRefs(cast<MachineSDNode>(NewN), {MemOp});
return;
}
}