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Re: wide-int branch updated.
- From: Kenneth Zadeck <zadeck at naturalbridge dot com>
- To: Richard Biener <rguenther at suse dot de>
- Cc: Richard Sandiford <r dot sandiford at uk dot ibm dot com>, Mike Stump <mrs at mrs dot kithrup dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 28 Aug 2013 08:04:33 -0400
- Subject: Re: wide-int branch updated.
- Authentication-results: sourceware.org; auth=none
- References: <521CE56E dot 5010605 at naturalbridge dot com> <alpine dot LNX dot 2 dot 00 dot 1308280940340 dot 20077 at zhemvz dot fhfr dot qr>
On 08/28/2013 03:45 AM, Richard Biener wrote:
no, because anything that comes in at precision 0 is a canonized sign
extended number already. the precision 0 just means that it is safe to
be any precision.
On Tue, 27 Aug 2013, Kenneth Zadeck wrote:
removed all knowledge of SHIFT_COUNT_TRUNCATED from wide-int
both Richard Biener and Richard Sandiford had commented negatively about
fixed bug with wide-int::fits_uhwi_p.
wide_int_ro::fits_uhwi_p () const
- return (len == 1 && val >= 0) || (len == 2 && val == 0);
+ return (precision <= HOST_BITS_PER_WIDE_INT)
+ || (len == 1 && val >= 0)
+ || (len == 2 && (precision >= 2 * HOST_BITS_PER_WIDE_INT) && (val
+ || (len == 2 && (sext_hwi (val, precision &
- 1)) == 0));
it now get's scary ;) Still wrong for precision == 0?
I wonder what it's semantic is ... in double_int we simply require
high == 0 (thus, negative numbers are not allowed). with
precision <= HOST_BITS_PER_WIDE_INT you allow negative numbers.
Matching what double-int fits_uhwi does would be
(len == 1 && ((signed HOST_WIDE_INT)val) >= 0)
it is signed so i am matching this part.
so this does not work. say i had a precision 70 bit wide-int. The bits
above the precision are undefined, so i have to clear it out. This is
what the two lines at len 2 are for. However if the precision is
greater than 2 hwi's then we can do something this simple.
|| (len == 2 && val == 0)
(I don't remember off-hand the signedness of val, but eventually
you missed the conversion to signed)
Now, what double-int does is supposed to match
host_integerp (..., 1) which I think it does.