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Re: wide-int branch updated.


On 08/28/2013 03:45 AM, Richard Biener wrote:
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
this.

fixed bug with wide-int::fits_uhwi_p.
  inline bool
  wide_int_ro::fits_uhwi_p () const
  {
-  return (len == 1 && val[0] >= 0) || (len == 2 && val[1] == 0);
+  return (precision <= HOST_BITS_PER_WIDE_INT)
+    || (len == 1 && val[0] >= 0)
+    || (len == 2 && (precision >= 2 * HOST_BITS_PER_WIDE_INT) && (val[1]
==
0))
+    || (len == 2 && (sext_hwi (val[1], precision &
(HOST_BITS_PER_WIDE_INT
- 1)) == 0));
  }

it now get's scary ;)  Still wrong for precision == 0?
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.
;)

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]) >= 0)
it is signed so i am matching this part.
|| (len == 2 && val[1] == 0)
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.

kenny
(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.

Richard.


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