[PATCH][4.3] Deprecate -ftrapv

[Paolo Bonzini]

>> Well presumably one would want to use target dependent stuff for
>> detecting overflow where it exists (sticky overflow bits on
>> power, O flag on PC, trapping add on MIPS etc).
> 
> On the whole I think you'd want to benefit from tree-ssa optimizing 
> overflow checks where possible (including optimizing them away with VRP), 
> if you hope for a -ftrapv that could be turned on by default for Ada with 
> performance impact as small as possible.  That would suggest back ends 
> matching overflow-check patterns and converting them into such
> instructions.

Yes, fully fully agreed.

Paolo