Add -Wtautological-value-range-compare warning.

Authored by rsmith on Aug 4 2020, 3:33 PM.


Add -Wtautological-value-range-compare warning.

This warning diagnoses cases where an expression is compared to a
constant, and the comparison is tautological due to the form of the
expression (but not merely due to its type). This applies in cases such
as comparisons of bit-fields and the result of bit-masks.

The new warning is added to the Clang diagnostic group
-Wtautological-constant-in-range-compare but not to the
formerly-equivalent GCC-compatibility diagnostic group -Wtype-limits,
which retains its old meaning of diagnosing only tautological
comparisons to extremal values of a type (eg, int > INT_MAX).

Reviewed By: rtrieu

Differential Revision: https://reviews.llvm.org/D85256