[X86] Use nneg flag when trying to convert uitofp -> sitofp

Author: goldsteinn

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -48267,7 +48267,7 @@ static SDValue combineAndShuffleNot(SDNode *N, SelectionDAG &DAG,
 
   // We do not split for SSE at all, but we need to split vectors for AVX1 and
   // AVX2.
-  if (!Subtarget.useAVX512Regs() && VT.is512BitVector() && 
+  if (!Subtarget.useAVX512Regs() && VT.is512BitVector() &&
       TLI.isTypeLegal(VT.getHalfNumVectorElementsVT(*DAG.getContext()))) {
     SDValue LoX, HiX;
     std::tie(LoX, HiX) = splitVector(X, DAG, DL);
@@ -54062,7 +54062,8 @@ static SDValue combineUIntToFP(SDNode *N, SelectionDAG &DAG,
   // Since UINT_TO_FP is legal (it's marked custom), dag combiner won't
   // optimize it to a SINT_TO_FP when the sign bit is known zero. Perform
   // the optimization here.
-  if (DAG.SignBitIsZero(Op0)) {
+  SDNodeFlags Flags = N->getFlags();
+  if (Flags.hasNonNeg() || DAG.SignBitIsZero(Op0)) {
     if (IsStrict)
       return DAG.getNode(ISD::STRICT_SINT_TO_FP, SDLoc(N), {VT, MVT::Other},
                          {N->getOperand(0), Op0});