Hi Richard,
Great to see that you're addressing this issue. If I understand
correctly,
for RTL all operations are always wrapping, right?
I have been considering adding "V" variants for operations that trap on
overflow. The main reason I have not (yet) pursued this, is the daunting
task of teaching the folders about all these new codes. initially I'd
like to lower the "V" operations to explicit checks (calling abort() or
raising an exception, depending on the language) during gimplification,
but with the idea of eventually delaying expansion as more code learns
how to handle the new expressions. I already have most of the code
necessary
for the expansions, as I now do them during translation of Ada trees to
GENERIC trees. Actually, the new and saner wrapping semantics for
{PLUS,MINUS,MULT}_EXPR simplify these a bit, by avoiding the need to use
unsigned types.
As you obviously doing something very similar now by introducing "NV"
variants,
do you think this would fit in with your scheme? If so, I'd be happy
to try
and expand on your work to have, wrapping, no-overflow and overflow-
checking
variants for basic arithmetic.
-Geert
