nir_algebraic_pattern_test can validate shaders with the following
structure:
%0 = @provide(base = 0)
...
%N = @provide(base = input_count)
// multiple equivalent expressions
a = ...
b = ...
valid = ieq(a, b)
@use(valid)
Expressions are evaluated by emulating the shader using
nir_eval_const_opcode.
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39076>
