On 22/03/2023 13:56, Richard Biener wrote:
Basically, the -ffast-math instructions will always be the fastest way,
but the goal is that the default optimization shouldn't just disable
vectorization entirely for any loop that has a divide in it.
We try to express division as multiplication, but yes, I think there's
currently no way to tell the vectorizer that vectorized division is
available as libcall (nor for any other arithmetic operator that is not
a call in the first place).
I have considered creating a new builtin code, similar to the libm
functions, that would be enabled by a backend hook, or maybe just if
TARGET_VECTORIZE_BUILTIN_VECTORIZED_FUNCTION doesn't return NULL. The
vectorizer would then use that, somehow. To treat it just like any other
builtin it would have to be set before the vectorizer pass encounters
it, which is probably not ideal for all the other passes that want to
handle divide operators. Alternatively, the vectorizable_operation
function could detect and introduce the builtin where appropriate.
Would this be acceptable, or am I wasting my time planning something
that would get rejected?
Thanks
Andrew
