[llvm-branch-commits] [llvm] [SelectionDAG] Deal with POISON for INSERT_VECTOR_ELT/INSERT_SUBVECTOR (part 2) (PR #143103)

[Björn Pettersson via llvm-branch-commits]

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@@ -5454,6 +5454,59 @@ bool SelectionDAG::isGuaranteedNotToBeUndefOrPoison(SDValue Op,
     }
     return true;
 
+  case ISD::INSERT_SUBVECTOR: {
+    if (Op.getValueType().isScalableVector())
+      break;
+    SDValue Src = Op.getOperand(0);
+    SDValue Sub = Op.getOperand(1);
+    uint64_t Idx = Op.getConstantOperandVal(2);
+    unsigned NumSubElts = Sub.getValueType().getVectorNumElements();
+    APInt DemandedSubElts = DemandedElts.extractBits(NumSubElts, Idx);
+    APInt DemandedSrcElts = DemandedElts;
+    DemandedSrcElts.clearBits(Idx, Idx + NumSubElts);
+
+    if (!!DemandedSubElts && !isGuaranteedNotToBeUndefOrPoison(
+                                 Sub, DemandedSubElts, PoisonOnly, Depth + 1))
+      return false;
+    if (!!DemandedSrcElts && !isGuaranteedNotToBeUndefOrPoison(
+                                 Src, DemandedSrcElts, PoisonOnly, Depth + 1))
+      return false;
+    return true;
+  }
+
+  case ISD::INSERT_VECTOR_ELT: {
+    SDValue InVec = Op.getOperand(0);
+    SDValue InVal = Op.getOperand(1);
+    SDValue EltNo = Op.getOperand(2);
+    EVT VT = InVec.getValueType();
+    auto *IndexC = dyn_cast<ConstantSDNode>(EltNo);
+    if (IndexC && VT.isFixedLengthVector() &&
+        IndexC->getZExtValue() < VT.getVectorNumElements()) {
+      if (DemandedElts[IndexC->getZExtValue()] &&
+          !isGuaranteedNotToBeUndefOrPoison(InVal, PoisonOnly, Depth + 1))
+        return false;
+      APInt InVecDemandedElts = DemandedElts;
+      InVecDemandedElts.clearBit(IndexC->getZExtValue());
+      if (!!InVecDemandedElts &&
+          !isGuaranteedNotToBeUndefOrPoison(
+              peekThroughInsertVectorElt(InVec, InVecDemandedElts),
+              InVecDemandedElts, PoisonOnly, Depth + 1))
+        return false;
+      return true;
+    }
+    break;
+  }
+
+  case ISD::SCALAR_TO_VECTOR:
+    // If only demanding upper (undef) elements.
+    if (DemandedElts.ugt(1))
+      return PoisonOnly;
+    // If only demanding element 0, or only considering poison.
+    if (PoisonOnly || DemandedElts == 0)
----------------
bjope wrote:

Should be DemandedElts == 1 here.

https://github.com/llvm/llvm-project/pull/143103