Jeff Law wrote:
> + if (required_align > MAX_SUPPORTED_STACK_ALIGNMENT)
> + {
> + extra = (required_align - MAX_SUPPORTED_STACK_ALIGNMENT)
> + / BITS_PER_UNIT;
> + size = plus_constant (Pmode, size, extra);
> + size = force_operand (size, NULL_RTX);
>
> - if (extra && size_align > BITS_PER_UNIT)
> - size_align = BITS_PER_UNIT;
> + if (flag_stack_usage_info && pstack_usage_size)
> + *pstack_usage_size += extra;
> + }
> So it's unclear to me why you increase the size iff REQUIRED_ALIGN is
> greater than MAX_SUPPORTED_STACK_ALIGNMENT.
>
> ISTM the safe assumption we can make in this code is that the stack is
> aligned to STACK_BOUNDARY. If so, isn't the right test
>
> (required_align > STACK_BOUNDARY)?
>
> And once we decide to make an adjustment, isn't the right adjustment to
> make (required_align - STACK_BOUNDARY) / BITS_PER_UNIT?
>
> I feel like I must be missing something really important here.
Yes I think you're right that if STACK_BOUNDARY is the guaranteed stack
alignment, it should check against STACK_BOUNDARY indeed.
But then the check size_align % MAX_SUPPORTED_STACK_ALIGNMENT != 0
seems wrong too given that round_push uses a different alignment to align to.
Wilco
