------- Comment #2 from fxcoudert at gcc dot gnu dot org 2007-03-20 09:27
-------
Here's a patch:
Index: trans-const.c
===================================================================
--- trans-const.c (revision 123017)
+++ trans-const.c (working copy)
@@ -165,23 +165,31 @@
}
else
{
- unsigned HOST_WIDE_INT words[2];
- size_t count;
+ unsigned HOST_WIDE_INT *words;
+ size_t count, numb;
+ /* Determine the number of unsigned HOST_WIDE_INT that are required
+ for represent the value. */
+ numb = 8*sizeof(HOST_WIDE_INT);
+ count = (mpz_sizeinbase (i, 2) + numb-1) / numb;
+ if (count < 2)
+ count = 2;
+ words = (unsigned HOST_WIDE_INT *) alloca (count *
sizeof(HOST_WIDE_INT));
+
/* Since we know that the value is not zero (mpz_fits_slong_p),
we know that at least one word will be written, but we don't know
about the second. It's quicker to zero the second word before
than conditionally clear it later. */
words[1] = 0;
-
+
/* Extract the absolute value into words. */
- mpz_export (words, &count, -1, sizeof (HOST_WIDE_INT), 0, 0, i);
+ mpz_export (words, &count, -1, sizeof(HOST_WIDE_INT), 0, 0, i);
- /* We assume that all numbers are in range for its type, and that
- we never create a type larger than 2*HWI, which is the largest
- that the middle-end can handle. */
- gcc_assert (count == 1 || count == 2);
-
+ /* We don't assume that all numbers are in range for its type.
+ However, we never create a type larger than 2*HWI, which is the
+ largest that the middle-end can handle. So, we only take the
+ first two elements of words, which is equivalent to wrapping the
+ value if it's larger than the type range. */
low = words[0];
high = words[1];
And there's a small testcase, to see that the constant trees created for
overflowing values have the same value than the naturally overflowing
calculation done at run-time:
$ cat uu.f90
integer :: a
integer(kind=8) :: b
a = -3
b = -huge(b) / 7
a = a ** 73
b = 7894_8 * b - 78941_8
print *, (-3)**73, a
print *, 7894_8 * (-huge(b) / 7) - 78941_8, b
end
$ gfortran -fno-range-check uu.f90 && ./a.out
-1534976995 -1534976995
2635249153387000989 2635249153387000989
--
fxcoudert at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |patch
Known to fail| |4.1.3 4.2.0 4.3.0
Summary|-fno-range-check can trigger|-fno-range-check with large
|ICE |integer values triggers ICE
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31262
