[Bug rtl-optimization/323] optimized code gives strange floating point results

[guillaume dot melquiond at ens-lyon dot fr]

------- Comment #95 from guillaume dot melquiond at ens-lyon dot fr  2007-04-03 17:51 -------
> I think that Uros' patch to add a -mpc switch for precision control would
> "fix" this.
> The real fix would be to automatically insert fldcw instructions before
> float/double operations, in order to limit the precision of the operations.
> But I think that it would kill speed even more than -ffloat-store.

Unfortunately, it is not that simple. The -mpc switch and the fldcw
instructions control the size of the significant, but they don't control the
range of the exponent. So it will solve the issue with the first testcase of
this bug-report, but you could still build examples where two execution paths
that perform the same floating-point computations produce completely different
results.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=323