On a target with a 16-bit mask (for example), we would choose the type
of an integer literal "1024" to be an int16. Previously, we used an int32,
which is a worse fit and leads to less efficient code than an int16
on a 16-bit mask target. (However, we'd still give an integer literal
1000000 the type int32, even in a 16-bit target.)
Updated the tests to still pass with 8 and 16-bit targets, given this
change.
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
For associative atomic ops (add, and, or, xor), we can take advantage of
their associativity to do just a single hardware atomic instruction,
rather than one for each of the running program instances (as the previous
implementation did.)
The basic approach is to locally compute a reduction across the active
program instances with the given op and to then issue a single HW atomic
with that reduced value as the operand. We then take the old value that
was stored in the location that is returned from the HW atomic op and
use that to compute the values to return to each of the program instances
(conceptually representing the cumulative effect of each of the preceding
program instances having performed their atomic operation.)
Issue #56.
