[llvm] [DAG] SelectionDAG.computeKnownBits - add NSW/NUW flags support to ISD::SHL handling (PR #89877)

[Matt Arsenault via llvm-commits]

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@@ -3492,16 +3492,23 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
       Known.Zero.setBitsFrom(1);
     break;
   }
-  case ISD::SHL:
+  case ISD::SHL: {
     Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
     Known2 = computeKnownBits(Op.getOperand(1), DemandedElts, Depth + 1);
-    Known = KnownBits::shl(Known, Known2);
+
+    bool NUW = Op.getNode()->Flags.hasNoUnsignedWrap();
+    bool NSW = Op.getNode()->Flags.hasNoSignedWrap();
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arsenm wrote:

Think you can do Op->getFlags instead of getNode()->Flags 

https://github.com/llvm/llvm-project/pull/89877