On 11/11/06, Revital1 Eres <[EMAIL PROTECTED]> wrote:
Hello, -fno-rounding-math enables the transformation of (-(X - Y)) -> (Y - X) in simplify-rtx.c which seems to be the same transformation that enabled by -funsafe-math-optimizations in fold-const.c. If I understand currently -frounding-math means that the rounding mode is important. In that case should there be correlation between -funsafe-math-optimizations and -fno-rounding-math (which currently does not exist)?
I think the simplify-rtx.c code is partly wrong, as it changes behavior with signed zeros. I don't know off-hand if -(X - Y) and Y - X behave the same in rounding if the rounding mode is round to nearest, but certainly for round to +Inf it will differ. So HONOR_SIGNED_ZEROS (mode) && !flag_rounding_math might be the correct predicate here (and in the fold-const.c case). But floating point rounding scares me ;) Richard.
