> I just noticed something very surprising. There's a clause in > general_operand (recog.c): > > if (! volatile_ok && MEM_VOLATILE_P (op)) > return 0; > > Oh... so, a MEM_VOLATILE_P is _not_ a general operand? Why? This is also > not referred to in the documentation of general operand so it kind of > caught me by surprise.
It's more of the other way around: MEM_VOLATILE_P is a general operand unless explicitly requested via init_recog_no_volatile. Some passes, like combine, don't track the volatileness of operands precisely, so they disable their manipulation altogether to avoid generating wrong code. -- Eric Botcazou
