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Re: ix86_data_alignment: bad defaults?
> It is to improve performance of string functions on larger chunks of
> data. x86-64 specify this, for x86 it is optional. I don't think we
> should end up warning here - it is done only for static variables where
> the alignment can be higher than what BIGGEST_ALIGNMENT promise.
Higher than BIGGEST_ALIGNMENT? So, maybe we should rename it
ALMOST_BIGGEST_ALIGNMENT? I'm confused.
The alignment warning came from varasm.c align_variable():
/* Some object file formats have a maximum alignment which they support.
In particular, a.out format supports a maximum alignment of 4. */
if (align > MAX_OFILE_ALIGNMENT)
{
warning (0, "alignment of %q+D (%d) is greater than maximum object "
"file alignment. Using %d", decl,
align / BITS_PER_UNIT,
MAX_OFILE_ALIGNMENT/BITS_PER_UNIT);
align = MAX_OFILE_ALIGNMENT;
}
In the failing case, MAX_OFILE_ALIGNMENT is 128 (it defaults to
BIGGEST_ALIGNMENT).
Failing code looks like this:
unsigned short __dj_ctype_flags[] = {
0, /* CTRL+?, 0xffff */
__dj_ISCNTRL, /* CTRL+@, 0x00 */
. . .
};