On 12/09/2013 10:01 AM, Richard Biener wrote:
On Mon, Dec 9, 2013 at 3:49 PM, Kenneth Zadeck <zad...@naturalbridge.com> wrote:
On 12/08/2013 05:35 AM, Richard Biener wrote:
Richard Sandiford <rdsandif...@googlemail.com> wrote:
Kenneth Zadeck <zad...@naturalbridge.com> writes:
#define WIDE_INT_MAX_ELTS \
- ((4 * MAX_BITSIZE_MODE_ANY_INT + HOST_BITS_PER_WIDE_INT - 1) \
- / HOST_BITS_PER_WIDE_INT)
+ (((MAX_BITSIZE_MODE_ANY_INT + HOST_BITS_PER_WIDE_INT - 1) \
+ / HOST_BITS_PER_WIDE_INT) + 1)
I think this should be:
(MAX_BITSIZE_MODE_ANY_INT / HOST_BITS_PER_WIDE_INT + 1)
We only need an extra HWI if MAX_BITSIZE_MODE_ANY_INT is an exact
multiple
of HOST_BITS_PER_WIDE_INT.
we will do this later when some other issues that Eric B raised are
settled.
I think you're talking about defining MAX_BITSIZE_MODE_ANY_INT as
MAX_SIZE_MODE_ANY_INT * BITS_PER_UNIT, but that's orthogonal to the
change above. IMO it doesn't make sense to both round up the
division
and also add 1 to the result. So I think we should make this change
regardless of whatever follows.
Looks good to me otherwise, thanks.
Richard
so this one works the way you want. While it is true the the
problems
are disjoint, the solution will likely evolving change the same lines
of
source in two different ways.
Well, if we're changing the definition of WIDE_INT_MAX_ELTS now (and we
are)
I think we should change it to something that makes sense. All we want
is
1 extra bit. We don't need to round up the size and then add a whole
HWI on top. Doing that will potentially pessimise targets that don't
need anything beyond SImode.
I agree.
Richard.
Done, ok to commit?
+ early examination of the target's mode file. The WIDE_INT_MAX_ELTS
+ can accomodate at least 1 more bit so that unsigned numbers of that
+ mode can be represented. Note that it is still possible to create
+ fixed_wide_ints that have precisions greater than
+ MAX_BITSIZE_MODE_ANY_INT. This can be useful when representing a
+ double-width multiplication result, for example. */
#define WIDE_INT_MAX_ELTS \
- ((4 * MAX_BITSIZE_MODE_ANY_INT + HOST_BITS_PER_WIDE_INT - 1) \
- / HOST_BITS_PER_WIDE_INT)
+ (((MAX_BITSIZE_MODE_ANY_INT + HOST_BITS_PER_WIDE_INT - 1) \
+ / HOST_BITS_PER_WIDE_INT))
+
that doesn't reserve 1 more bit, it just rounds up. For one more bit you
need to add 1, so
#define WIDE_INT_MAX_ELTS \
+ (((MAX_BITSIZE_MODE_ANY_INT + 1 + HOST_BITS_PER_WIDE_INT - 1) \
+ / HOST_BITS_PER_WIDE_INT))
no?
oops? i am testing it correctly this time. Will report back in an hour.
kenny
Otherwise ok.
Thanks,
Richard.
kenny
It's not like I can approve the patch anyway though, so I'll leave it
there.
Thanks,
Richard
