Now, if a struct member has an explicit 'uniform' or 'varying'
qualifier, then that member has that variability, regardless of
the variability of the struct's variability. Members without
'uniform' or 'varying' have unbound variability, and in turn
inherit the variability of the struct.
As a result of this, now structs can properly be 'varying' by default,
just like all the other types, while still having sensible semantics.
Previously, it was only in the GatherScatterFlattenOpt optimization pass that
we added the per-lane offsets when we were indexing into varying data.
(Specifically, the case of float foo[]; int index; foo[index], where foo
is an array of varying elements rather than uniform elements.) Now, this
is done in the front-end as we're first emitting code.
In addition to the basic ugliness of doing this in an optimization pass,
it was also error-prone to do it there, since we no longer have access
to all of the type information that's around in the front-end.
No functionality or performance change.
scalar values (that ispc used to smear across the array/struct
elements). Now, initializers in variable declarations must be
{ }-delimited lists, with one element per struct member or array
element, respectively.
There were a few problems with the previous implementation of the
functionality to initialize from scalars. First, the expression
would be evaluated once per value initialized, so if it had side-effects,
the wrong thing would happen. Next, for large multidimensional arrays,
the generated code would be a long series of move instructions, rather
than loops (and this in turn made LLVM take a long time.)
While both of these problems are fixable, it's a non-trivial
amount of re-plumbing for a questionable feature anyway.
Fixes issue #50.
