[mlir] Implement inferResultRanges for vector.step op (#151536)

Implements the `inferResultRanges` method from the
`InferIntRangeInterface` interface for `vector.step`. The implementation
is similar to that of arith.constant, since the exact result values are
statically known.

Signed-off-by: Max Dawkins <[email protected]>

Author: Max191

mlir/include/mlir/Dialect/Vector/IR/VectorOps.td

@@ -2877,7 +2877,10 @@ def Vector_ScanOp :
 // VectorStepOp
 //===----------------------------------------------------------------------===//
 
-def Vector_StepOp : Vector_Op<"step", [Pure]> {
+def Vector_StepOp : Vector_Op<"step", [
+    Pure,
+    DeclareOpInterfaceMethods<InferIntRangeInterface, ["inferResultRanges"]>
+  ]> {
   let summary = "A linear sequence of values from 0 to N";
   let description = [{
     A `step` operation produces an index vector, i.e. a 1-D vector of values of

mlir/lib/Dialect/Vector/IR/VectorOps.cpp

@@ -7202,6 +7202,23 @@ Value mlir::vector::makeArithReduction(OpBuilder &b, Location loc,
   return selectPassthru(b, mask, result, acc);
 }
 
+//===----------------------------------------------------------------------===//
+// StepOp
+//===----------------------------------------------------------------------===//
+
+void StepOp::inferResultRanges(ArrayRef<ConstantIntRanges> argRanges,
+                               SetIntRangeFn setResultRanges) {
+  auto resultType = cast<VectorType>(getType());
+  if (resultType.isScalable()) {
+    return;
+  }
+  unsigned bitwidth = ConstantIntRanges::getStorageBitwidth(resultType);
+  APInt zero(bitwidth, 0);
+  APInt high(bitwidth, resultType.getDimSize(0) - 1);
+  ConstantIntRanges result = {zero, high, zero, high};
+  setResultRanges(getResult(), result);
+}
+
 //===----------------------------------------------------------------------===//
 // Vector Masking Utilities
 //===----------------------------------------------------------------------===//

mlir/test/Dialect/Vector/int-range-interface.mlir

@@ -108,3 +108,11 @@ func.func @test_vector_extsi() -> vector<2xi32> {
   %2 = test.reflect_bounds %1 : vector<2xi32>
   func.return %2 : vector<2xi32>
 }
+
+// CHECK-LABEL: func @vector_step
+// CHECK: test.reflect_bounds {smax = 7 : index, smin = 0 : index, umax = 7 : index, umin = 0 : index}
+func.func @vector_step() -> vector<8xindex> {
+  %0 = vector.step : vector<8xindex>
+  %1 = test.reflect_bounds %0 : vector<8xindex>
+  func.return %1 : vector<8xindex>
+}