[PATCH] D141891: [VP][DAGCombiner] Introduce generalized pattern match for vp sdnodes.

[Yeting Kuo via Phabricator via llvm-commits]

fakepaper56 added inline comments.


================
Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:854
+  SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT, SDValue Operand,
+                  Optional<SDNodeFlags> Flags = std::nullopt) {
+      if (Flags)
----------------
craig.topper wrote:
> fakepaper56 wrote:
> > craig.topper wrote:
> > > We don't usually use Optional for Flags. We just default it to SDNodeFlags()
> > I think using Optional is to represent both DAG.getCode() w/ SDNodeFlags and DAG.getCode()  w/o SDNodeFlags.
> The SelectionDAG::getNode functions being called always take an SDNodeFlags they just default construct one if it isn't passed explicitly. Why can't we do the same in the context?
I think  `SelectionDAG::getNode` uses `FlagInserter` when not having `SDNodeFlags` argument. The below code is the reason why I think so,
```
SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
                              SDValue Operand) {
  SDNodeFlags Flags;
  if (Inserter)
    Flags = Inserter->getFlags();
  return getNode(Opcode, DL, VT, Operand, Flags);
}
```


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  https://reviews.llvm.org/D141891/new/

https://reviews.llvm.org/D141891