[SelectionDAG] Better ISD::ANY_EXTEND/ISD::ANY_EXTEND_VECTOR_INREG ComputeKnownBits support

Add DemandedElts handling to ISD::ANY_EXTEND and add missing ISD::ANY_EXTEND_VECTOR_INREG handling. Despite the lack of test changes this code IS being used - its just that the ANY_EXTEND ops are legalized later on (typically to ZERO_EXTEND equivalents) so we typically manage to combine later on.

Author: RKSimon

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -3099,8 +3099,15 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     Known = Known.sext(BitWidth);
     break;
   }
+  case ISD::ANY_EXTEND_VECTOR_INREG: {
+    EVT InVT = Op.getOperand(0).getValueType();
+    APInt InDemandedElts = DemandedElts.zextOrSelf(InVT.getVectorNumElements());
+    Known = computeKnownBits(Op.getOperand(0), InDemandedElts, Depth + 1);
+    Known = Known.zext(BitWidth, false /* ExtendedBitsAreKnownZero */);
+    break;
+  }
   case ISD::ANY_EXTEND: {
-    Known = computeKnownBits(Op.getOperand(0), Depth+1);
+    Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
     Known = Known.zext(BitWidth, false /* ExtendedBitsAreKnownZero */);
     break;
   }