On Wed, Feb 20, 2019 at 06:29:06PM +0000, Joseph Myers wrote:
> On Wed, 20 Feb 2019, Jakub Jelinek wrote:
>
> > + /* mpc_norm assumes it can square a number without bothering with
> > + with range scaling, so until that is fixed, double the minimum
> > + and maximum exponents, plus add some buffer for arithmetics
> > + on the squared numbers. */
>
> Note that I think such issues are pervasive in MPC; it's not just that one
> function. MPFR is generally careful about using a larger exponent range
> internally (there might still be issues with very big exponents where they
> aren't handled specially to avoid internal overflow, but the maximum MPFR
> exponent range is very large); MPC doesn't generally try to handle
> restricted exponent ranges.
I've added E.g. to the comment, is that sufficient, or are you aware of some
mpc computation that will misbehave even with those 2 * max_exp + 2 etc.
ranges?
Bootstrapped/regtested now on x86_64-linux and i686-linux successfully and
various people tested it on other targets, ok for trunk?
2019-02-20 Jakub Jelinek <ja...@redhat.com>
PR middle-end/88074
PR middle-end/89415
* toplev.c (do_compile): Double the emin/emax exponents to workaround
buggy mpc_norm.
* gcc.dg/pr88074-2.c: New test.
--- gcc/toplev.c.jj 2019-02-20 10:00:49.290492694 +0100
+++ gcc/toplev.c 2019-02-20 14:04:27.037769362 +0100
@@ -2173,8 +2173,12 @@ do_compile ()
max_exp = fmt->emax;
}
}
- if (mpfr_set_emin (min_exp)
- || mpfr_set_emax (max_exp))
+ /* E.g. mpc_norm assumes it can square a number without bothering with
+ with range scaling, so until that is fixed, double the minimum
+ and maximum exponents, plus add some buffer for arithmetics
+ on the squared numbers. */
+ if (mpfr_set_emin (2 * (min_exp - 1))
+ || mpfr_set_emax (2 * (max_exp + 1)))
sorry ("mpfr not configured to handle all float modes");
/* Set up the back-end if requested. */
--- gcc/testsuite/gcc.dg/pr88074-2.c.jj 2019-02-20 14:10:07.109140297 +0100
+++ gcc/testsuite/gcc.dg/pr88074-2.c 2019-02-20 14:09:46.696478179 +0100
@@ -0,0 +1,17 @@
+/* PR middle-end/88074 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-add-options float128 } */
+/* { dg-require-effective-target float128 } */
+/* { dg-final { scan-tree-dump-not "link_error " "optimized" } } */
+
+extern void link_error (void);
+int
+main ()
+{
+ if (((__FLT128_MAX__ * 0.5 + __FLT128_MAX__ * 0.5i)
+ / (__FLT128_MAX__ * 0.25 + __FLT128_MAX__ * 0.25i))
+ != (_Complex _Float128) 2)
+ link_error ();
+ return 0;
+}
Jakub
