[llvm-branch-commits] [llvm] DAG: Handle AssertNoFPClass in computeKnownBits (PR #167289)

[Yingwei Zheng via llvm-branch-commits]

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@@ -4121,6 +4121,27 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     Known.One.clearLowBits(LogOfAlign);
     break;
   }
+  case ISD::AssertNoFPClass: {
+    Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
+
+    FPClassTest NoFPClass =
+        static_cast<FPClassTest>(Op.getConstantOperandVal(1));
+    const FPClassTest NegativeTestMask = fcNan | fcNegative;
+    if ((NoFPClass & NegativeTestMask) == NegativeTestMask) {
+      // Cannot be negative.
+      Known.Zero.setSignBit();
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dtcxzyw wrote:

Use `makeNegative/makeNonNegative`. If there are conflict bits the value is poison.

https://github.com/llvm/llvm-project/pull/167289