On Fri, 6 Dec 2019, Richard Biener wrote:
nop_convert sees that 'a' comes from a conversion, and only returns d
(unlike 'convert?' which would try both a and d).
Maybe I should have formulated it as: nop_convert works kind of like a
strip_nops.
If use gets more and more we can make nop_convert a first class citizen and
allow a? Variant.
One reason I did not specifically push for that is that nop_convert is
seldom the right condition. It is convenient because it is usually easy
enough to check that it is correct, but in most cases one of narrowing /
zero-extension / sign-extension also works. Still, it is better to handle
just NOPs than no conversion at all, so I guess making that easy is still
good.
Like the attached (need to adjust docs & rename some functions still)
which generalizes
[digit]? parsing. This allows you to write (nop_convert? ...)
I guess once this is in, we should replace all (most?) 'nop_convert' with
'nop_convert?' (and possibly a digit in some places) and remove the last
alternative in the definition of nop_convert.
Although that will increase the code size. In case, we could still have
both a nop_convert and a strip_nop predicates. Just thinking:
(match (nop_convert @0)
(convert @0)
(if (tree_nop_conversion_p (type, TREE_TYPE (@0)))))
(match (nop_convert @0)
(view_convert @0)
(if (VECTOR_TYPE_P (type) && VECTOR_TYPE_P (TREE_TYPE (@0))
&& known_eq (TYPE_VECTOR_SUBPARTS (type),
TYPE_VECTOR_SUBPARTS (TREE_TYPE (@0)))
&& tree_nop_conversion_p (TREE_TYPE (type), TREE_TYPE (TREE_TYPE (@0))))))
(match (strip_nops @0)
(nop_convert? @0))
but that relies on the fact that when there is an optional operation, the
machinery first tries with the operation, and then without, the order
matters. Maybe being explicit on the priorities is safer
(match (strip_nops @0)
(nop_convert @0))
(match (strip_nops @0)
@0)
It works (generated files are unchanged), so I guess I'll push it
after polishing.
It also extends the 1/2/3 grouping to be able to group like (plus
(nop_convert2? @0) (convert2? @1))
so either both will be present or none (meaning that when grouping you
can choose the "cheaper"
test for one in case you know the conversions will be the same).
Nice.
--
Marc Glisse
