[llvm] [SelectionDAG] Support integer promotion for VP_LOAD and VP_STORE (PR #81299)

[Lei Huang via llvm-commits]

================
@@ -2216,6 +2242,50 @@ SDValue DAGTypeLegalizer::PromoteIntOp_STORE(StoreSDNode *N, unsigned OpNo){
                            N->getMemoryVT(), N->getMemOperand());
 }
 
+SDValue DAGTypeLegalizer::PromoteIntOp_VP_STORE(VPStoreSDNode *N,
+                                                unsigned OpNo) {
+  SDValue DataOp = N->getValue();
+  SDValue Operand = N->getOperand(OpNo);
+
+  if (OpNo >= 4) {
+    // The Mask or EVL. Update in place.
+    EVT DataVT = DataOp.getValueType();
+    SDValue PromotedOperand = OpNo == 4 ? PromoteTargetBoolean(Operand, DataVT)
+                                        : ZExtPromotedInteger(Operand);
+    SmallVector<SDValue, 6> NewOps(N->op_begin(), N->op_end());
+    NewOps[OpNo] = PromotedOperand;
+    return SDValue(DAG.UpdateNodeOperands(N, NewOps), 0);
+  }
+
+  assert(OpNo == 1 && "Unexpected operand for promotion");
+  DataOp = GetPromotedInteger(DataOp);
+
+  assert(!N->isIndexed() && "expecting unindexed vp_store!");
+
+  return DAG.getTruncStoreVP(N->getChain(), SDLoc(N), DataOp, N->getBasePtr(),
+                             N->getMask(), N->getVectorLength(),
+                             N->getMemoryVT(), N->getMemOperand(),
+                             N->isCompressingStore());
+}
+
+SDValue DAGTypeLegalizer::PromoteIntOp_VP_LOAD(VPLoadSDNode *N, unsigned OpNo) {
+  assert(OpNo >= 3 && "Only know how to promote the mask or length!");
----------------
lei137 wrote:

But this function is meant to be used to promote either mask for length so the assert need to be 3 no?  Since:
* If `OpNo == 3` promote mask.
* If `OpNo ==4` promote length.

https://github.com/llvm/llvm-project/pull/81299