Re: [PATCH] Merging Cilk Plus into Trunk (Patch 1 of approximately 22)

[Richard Henderson <rth at redhat dot com>]

On 09/10/2012 09:09 AM, Iyer, Balaji V wrote:
>> >If that's the case, what's the point in defining an external ABI and defining what
>> >__attribute__((vector)) placed on a function declaration means?

> When you have __attribute__((vector)) you are asking the compiler to
> create a vector AND a scalar version of the function. The advantage
> is that if the function is used, for example, in 2 loops where 1 can
> be vectorized and another cannot, the vectorizable loop won't suffer
> (i.e. suffer from being not-vectorized).

You've totally mis-understood my point.

Whether or not the compiler creates a clone COULD BE totally up to the
compiler, based on whether or not vectorization is enabled, whether the
loop has been analyzed such that vectorization may proceed, or indeed
the phase of the moon.

But in order for that to happen, the clone must be totally private to
the module for which we are generating code (in the LTO sense, this is
the entire program or dll; without LTO, this is just the object file).
It means that we never attempt to generate clones for functions for
which the body of the function is not visible.

On the other hand, if you insist on assuming a clone exists merely
because a declaration bears an attribute, then you must address ALL
of the problems with respect to defining a stable ABI in the face of
different cpu revisions, different ISAs, and different vector lengths.

I've not seen you address ANY of these problems, despite having the
problem pointed out multiple times.


r~