[PATCH][4.3] Deprecate -ftrapv

[Robert Dewar]

Joern Rennecke wrote:

> Considering the trouble that you get when you try to generate branches in
> a non-branch expander, we should probably have alternate named patterns
> to be used in ports to processors that have no conditional trap facility,
> or where a conditional trap is more expensive than a well predictable
> conditional branch.

Note that even if this is the case (conditional trap more expensive), it
may be appropriate in -Os mode. A one-byte INTO instruction after every
add takes less space than conditional jump to trapping code. Of course
it is always interesting that less code = less i-cache pressure, and
so you get something back for that in practice, YMMV.