More SSE infrastructure

Richard Henderson rth@cygnus.com
Wed Jul 5 00:16:00 GMT 2000


On Tue, Jul 04, 2000 at 02:19:58AM +0200, Mark Kettenis wrote:
> It would make some sense though to make the __m128 type similar to the
> SSE registers.

I don't agree.  If you wanted v4sf, you can use v4sf in the source.
Though not, admittedly, with Intel's interface.  But you can get it
from GCC easily enough.

In any case, the question at hand has absolutely nothing to do with
SSE specifically, but rather what we should give GDB for describing
a 128-bit integer.

The GCC infrastructure currently prohibits representing full 
arithmetic on items larger than twice the host word size.  If you
take away the actual arithmetic, and just manipulate the things as
data (movement and such), then the only thing left in GCC that 
appears to have problems is debugging.

The current solution in the Cygnus tree is to force the use of
long long as the `host' word size.  Which slows down the compiler
significantly.  We're trying to figure a way out of that.

So, the object being, fix the debugging code to cope with integer
objects larger than twice the host word size.  And in order to do
that, we need to know what GDB needs to do its job.

In the original message I sent, perhaps only to the GCC list (oops),
I quoted a fragment from the stabs emitter, wherein we look to see
if it's easy to print the upper bound for the type.  If it isn't
easy, we just print -1.

So the question is, do we really have to print the correct upper
and lower bounds for the 128-bit type, or can we just use 0 and -1,
as the existing code would suggest.


r~


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