On 12/18/2013 03:23 PM, Diggory Hardy wrote:
Is this a known issue?
Yes, it's the excess precision problem on i386: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=323
Is it the same with later GCC versions?
GCC 4.5 has some fixes.
Is there a way I can turn on most optimisations while still getting exactly the same results as without optimisation?
You could compile with -mfpmath=sse -msse2, or you could set the floating point control word to restrict precision to 53 bits. The latter will cover doubles only, the issue can still surface with floats.
-- Florian Weimer / Red Hat Product Security Team
