http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50904
--- Comment #26 from rguenther at suse dot de <rguenther at suse dot de> 2011-12-02 15:02:27 UTC --- On Fri, 2 Dec 2011, burnus at gcc dot gnu.org wrote: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50904 > > Tobias Burnus <burnus at gcc dot gnu.org> changed: > > What |Removed |Added > ---------------------------------------------------------------------------- > CC|bur...@net-b.de |dominiq at lps dot ens.fr > > --- Comment #25 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-12-02 > 14:40:48 UTC --- > (In reply to comment #24) > > Every program that would break with non honoring explicit parantheses > > would also break if the bracketed expression would be explicitely > > computed into a temporary (without explicit parantheses). So it > > should be easy to construct a testcase if you have one that breaks > > without -fno-protect-parens. > > I vaguely recall that one of the Polyhedron benchmarks gets minutely out of > the > correctness-check tolerance range with -fno-protect-parens while it stays > within without. I think Dominique has a program where the effect is more > disastrous. The trivial example is (x + 2**52) - 2**52 which rounds x to an integer. Without parens we optimize away that rounding effect. Thus, real*8 x, tem x = 1.3d tem = x + 2.d**52 x = tem - 2.d**52 if (x.ne.1.0d) call abort should not fail (minus my fortran coding errors ;)) with -fprotect-parens
