nir/algebraic: support for power-of-two optimizations

Some optimizations, like converting integer multiply/divide into left/
right shifts, have additional constraints on the search expression.
Like requiring that a variable is a constant power of two.  Support
these cases by allowing a fxn name to be appended to the search var
expression (ie. "a#32(is_power_of_two)").

Signed-off-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir_search.c

@@ -127,6 +127,9 @@ match_value(const nir_search_value *value, nir_alu_instr *instr, unsigned src,
              instr->src[src].src.ssa->parent_instr->type != nir_instr_type_load_const)
             return false;
 
+         if (var->cond && !var->cond(instr, src, num_components, new_swizzle))
+            return false;
+
          if (var->type != nir_type_invalid) {
             if (instr->src[src].src.ssa->parent_instr->type != nir_instr_type_alu)
                return false;