[mlir] IntegerRangeAnalysis: don't loop over splat attr (#115229)

If the `DenseIntElementsAttr` is a splat value, there is no need to loop
over the entire attr. Instead, just update with the splat value.

Author: IanWood1

mlir/lib/Dialect/Arith/IR/InferIntRangeInterfaceImpls.cpp

@@ -40,6 +40,11 @@ void arith::ConstantOp::inferResultRanges(ArrayRef<ConstantIntRanges> argRanges,
     setResultRange(getResult(), ConstantIntRanges::constant(value));
     return;
   }
+  if (auto splatAttr = llvm::dyn_cast_or_null<SplatElementsAttr>(getValue())) {
+    setResultRange(getResult(), ConstantIntRanges::constant(
+                                    splatAttr.getSplatValue<APInt>()));
+    return;
+  }
   if (auto arrayCstAttr =
           llvm::dyn_cast_or_null<DenseIntElementsAttr>(getValue())) {
     std::optional<ConstantIntRanges> result;