It is certainly reasonable, but if it is true it means that the
compiler is capable on linux, x86_64 to impose a 16 byte alignment on
some object for all type of allocations. Then I would expect an
__attribute__ ((aligned (16)) for a user defined type to be obeyed as
well.
I haven't tested whether long doubles are actually allocated on 16
byte boundaries in all case (global, auto and dynamic), mainly
because the tests would be inconclusive, unless you see an alignment
< 16.
I just mentioned the data point to see if it did say anything to GCC
developers.
On Dec 21, 2006, at 4:23 PM, Tim Prince wrote:
Maurizio Vitale wrote:
Thanks. Now to add to my confusion, on my system __alignof(long
double) returns 16, which I presume means that all allocation,
static, dynamic and automatic for long double objects are 16 byte
aligned.
This is a reasonable choice, that long doubles would be aligned for
good performance, unless the alignment is over-ridden by a packed
or reduced alignment specification.
