Previously, we uniqued AtomicTypes, so that they could be compared
by pointer equality, but with forthcoming SOA variability changes,
this would become too unwieldy (lacking a more general / ubiquitous
type uniquing implementation.)
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.
Now, when a type is declared without an explicit "uniform" or "varying"
qualifier, its variability is unbound; depending on the context of the
declaration, the variability is later finalized.
Currently, in almost all cases, types with unbound variability are
resolved to varying types; the one exception is typecasts like:
"(int)1"; in this case, the fact that (int) has unbound variability
carries through to the TypeCastExpr, which in turn notices that the
expression being type cast has uniform type and in turn will resolve
(int) to (uniform int).
Fixes issue #127.
Pointers can be either uniform or varying, and behave correspondingly.
e.g.: "uniform float * varying" is a varying pointer to uniform float
data in memory, and "float * uniform" is a uniform pointer to varying
data in memory. Like other types, pointers are varying by default.
Pointer-based expressions, & and *, sizeof, ->, pointer arithmetic,
and the array/pointer duality all bahave as in C. Array arguments
to functions are converted to pointers, also like C.
There is a built-in NULL for a null pointer value; conversion from
compile-time constant 0 values to NULL still needs to be implemented.
Other changes:
- Syntax for references has been updated to be C++ style; a useful
warning is now issued if the "reference" keyword is used.
- It is now illegal to pass a varying lvalue as a reference parameter
to a function; references are essentially uniform pointers.
This case had previously been handled via special case call by value
return code. That path has been removed, now that varying pointers
are available to handle this use case (and much more).
- Some stdlib routines have been updated to take pointers as
arguments where appropriate (e.g. prefetch and the atomics).
A number of others still need attention.
- All of the examples have been updated
- Many new tests
TODO: documentation
Added support for resolving dimensions of multi-dimensional unsized arrays
from their initializer exprerssions (previously, only the first dimension
would be resolved.)
Added checks to make sure that no unsized array dimensions remain after
doing this (except for the first dimensision of array parameters to
functions.)
Substantial improvements and generalizations to the parsing and
declaration handling code to properly parse declarations involving
pointers. (No change to user-visible functionality, but this
lays groundwork for supporting a more general pointer model.)
Both uniform and varying function pointers are supported; when a function
is called through a varying function pointer, each unique function pointer
value across the running program instances is called once for the set of
active program instances that want to call it.
This code previously lived in FunctionCallExpr but is now part
of FunctionSymbolExpr. This change doesn't change any current
functionality, but lays groundwork for function pointers in
the language, where we'll want to do function call overload
resolution at other times besides when a function call is
actually being made.
