nir: Recognize a pattern for doing b2f without the opcode.

Since we have patterns based on b2f, generate them if we see the b2f
equivalent using an iand.  This is common when generating NIR from TGSI.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

src/glsl/nir/nir_opt_algebraic.py

@@ -99,6 +99,7 @@ optimizations = [
    # Emulating booleans
    (('fmul', ('b2f', a), ('b2f', b)), ('b2f', ('iand', a, b))),
    (('fsat', ('fadd', ('b2f', a), ('b2f', b))), ('b2f', ('ior', a, b))),
+   (('iand', 'a@bool', 1.0), ('b2f', a)),
    # Comparison with the same args.  Note that these are not done for
    # the float versions because NaN always returns false on float
    # inequalities.