nir: skip opt_loop_peel_initial_break if continue block only has phis

Doing that optimization wouldn't do anything useful in this case.

nir_block_has_non_copy() is used by opt_loop_peel_initial_break().

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31002>

src/compiler/nir/nir.c

@@ -3507,6 +3507,8 @@ nir_block_contains_work(nir_block *block)
       return true;
 
    nir_foreach_instr(instr, block) {
+      if (instr->type == nir_instr_type_phi)
+         continue;
       if (instr->type != nir_instr_type_alu ||
           !nir_op_is_vec_or_mov(nir_instr_as_alu(instr)->op))
          return true;