[mlir][polynomial] verify from_tensor coeff type

Use the coefficient type to verify if a tensor fits in a polynomial
ring. Downstream we had originally not specified the coefficient type
and just used the implied bit width of the coefficient modulus.  Now
that we specify the type, this is simpler.

Author: j2kun

mlir/lib/Dialect/Polynomial/IR/PolynomialOps.cpp

@@ -47,11 +47,8 @@ LogicalResult FromTensorOp::verify() {
     return diag;
   }
 
-  APInt coefficientModulus = ring.getCoefficientModulus().getValue();
-  unsigned cmodBitWidth = coefficientModulus.ceilLogBase2();
   unsigned inputBitWidth = getInput().getType().getElementTypeBitWidth();
-
-  if (inputBitWidth > cmodBitWidth) {
+  if (inputBitWidth > ring.getCoefficientType().getIntOrFloatBitWidth()) {
     InFlightDiagnostic diag = emitOpError()
                               << "input tensor element type "
                               << getInput().getType().getElementType()

mlir/test/Dialect/Polynomial/ops_errors.mlir

@@ -1,7 +1,7 @@
 // RUN: mlir-opt --split-input-file --verify-diagnostics %s
 
 #my_poly = #polynomial.int_polynomial<1 + x**1024>
-#ring = #polynomial.ring<coefficientType=i16, coefficientModulus=256:i32, polynomialModulus=#my_poly>
+#ring = #polynomial.ring<coefficientType=i16>
 !ty = !polynomial.polynomial<ring=#ring>
 
 func.func @test_from_tensor_too_large_coeffs() {