Re: Should -fcross-jumping be part of -O1?

[Gabriel Dos Reis <gdr at integrable-solutions dot net>]

Robert Dewar <dewar@gnat.com> writes:

| Gabriel Dos Reis wrote:
| 
| > Robert Dewar <dewar@gnat.com> writes:
| > | Scott Robert Ladd wrote:
| > | | > And then you have the IEEE-754/IEC-60559 purists who insistent
| > that
| > | > using the 80-bit registers is a platform-specific optimization that
| > | > destroys reproducibility.
| > | | Yes, and they are right but:
| > | | a) there is nothing in most language standards that requires
| > | reproducibility.
| > And that is a language lawyer point of the view that they usually
| > think completely useless for their tasks.  At some point, I think they
| > are right.

[...]

| Indeed if someone took that attitude that optimization must never affect
| floating-point accuracy, I would say that *this* is the language-lawyer
| position that ignores pragmatic reality!

I'm talking of the attitude that rejects outright reproducibility on
the ground that there is nothing in most language standards that requires
reproducibility.  In fact, nothing in most language standards requires
useful implementations.  So should usefulness be rejected outright?  
The answer should be no.  Usefulness includes many things, and depends
on the application.  If an application requires some degree of
reproducibility, it would be quite pointless to argue that nothing in
most language  standards require reproducibility.

| We are not talking minor slow downs here, but slow downs by a
| significant factor (which can easily be 2 or 3). Many users of fpt
| cannot even consider this level of inefficiency.

I know.  There are many and many. Many users of fpt also can't
understand why someone would value speed over correctness when
correctness is the purpose of the computation.

-- Gaby