[llvm] [DAG] Define computeConstantRange for VSCALE folding (PR #176027)

[Craig Topper via llvm-commits]

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@@ -4563,6 +4563,42 @@ SelectionDAG::computeOverflowForSignedMul(SDValue N0, SDValue N1) const {
   return OFK_Sometime;
 }
 
+ConstantRange SelectionDAG::computeConstantRange(SDValue Op,
+                                                 const APInt &DemandedElts,
+                                                 unsigned Depth) const {
+  EVT VT = Op.getValueType();
+  unsigned BitWidth = VT.getScalarSizeInBits();
+
+  if (Depth >= MaxRecursionDepth)
+    return ConstantRange::getFull(BitWidth);
+
+  if (ConstantSDNode *C = isConstOrConstSplat(Op, DemandedElts))
+    return ConstantRange(C->getAPIntValue());
+
+  unsigned Opcode = Op.getOpcode();
+  switch (Opcode) {
+  case ISD::VSCALE: {
+    const Function &F = getMachineFunction().getFunction();
+    const APInt &Multiplier = Op.getConstantOperandAPInt(0);
+    return getVScaleRange(&F, BitWidth).multiply(Multiplier);
+  }
+  default:
+    break;
+  }
+
+  return ConstantRange::getFull(BitWidth);
+}
+
+ConstantRange SelectionDAG::computeConstantRangeIncludingKnownBits(
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topperc wrote:

So the test cases don't test this patch?

https://github.com/llvm/llvm-project/pull/176027