Should -fcross-jumping be part of -O1?

[Ian Lance Taylor]

Robert Dewar <dewar@gnat.com> writes:

> Ian Lance Taylor wrote:
> 
> > Granted.  I was thinking of the ability to prove algorithm
> > characteristics based on the IEEE spec, which is something I've done
> > in the past.  To me that is accurate floating point.  But I can see
> > that others may think that accurate floating point means something
> > else.
> 
> You don't really mean what you are saying here. The IEEE spec is a
> hardware/software spec about the behavior of certain floating-point
> operations. It has hardly anything to say about the relationship
> between these operations and semantics of high level languages.

No, I do mean what I am saying.  Of course C doesn't give you any
useful guarantees (I haven't looked at the latest standard).  But you
can prove the algorithm in the abstract.  Then you can use gcc
-fno-fast-math -ffloat-store and get what you want--you don't even
need -ffloat-store if you are using software floating point.  So to me
accurate floating point means -fno-fast-math -ffloat-store.

But you are quite right that that is not what most people want, and
probably not what many people would expect.

Ian