message: reduce num_nonlocals to take just src instrs
  tgt instructions can either return a repeated pointer or poison if they want to create an extra ptr
diff: @@ -667,14 +667,7 @@ static void calculateAndInitConstants(Transform &t) {
  has_null_block = num_ptrinputs > 0 || nullptr_is_used || has_malloc ||
  has_ptr_load || has_fncall;
  - // + 1 is sufficient to give 1 degree of freedom for the target to trigger UB
  - // in case a different pointer from source is produced.
  - auto num_max_nonlocals_inst
  - = max(num_nonlocals_inst_src, num_nonlocals_inst_tgt);
  - if (num_nonlocals_inst_src && num_nonlocals_inst_tgt)
  - ++num_max_nonlocals_inst;
  -
  - num_nonlocals_src = num_globals_src + num_ptrinputs + num_max_nonlocals_inst +
  + num_nonlocals_src = num_globals_src + num_ptrinputs + num_nonlocals_inst_src +
  has_null_block;
  // Allow at least one non-const global for calls to change
  