[LLVMdev] Floating-Point Overflow check

[me22]

On 23 July 2010 07:20, Steffen Geißinger
<steffen.geissinger at googlemail.com> wrote:
>
> i need to check if an overflow of an floating-point arithmetic operation
> occured.
> Currently I'm doing something like this (for addition):
>
> (LHS > 0 && RHS > 0 && sum <= 0)  || (LHS < 0 && RHS < 0 && sum >= 0)
>

Two things:
1) Have you tried adding 2 float-max values together to see what you
get?  It's not a negative (on most platforms, at least).  IEEE
floating-point has "infinities".
2) That method doesn't even work for integers, since overflow in
signed addition is undefined, and compilers will, correctly, remove
the check as impossible.