This PR forces the external definition of SV_GroupID variables to 3-vectors.
The conversion process between the shader-declared type and the external type
happens in wrapped main IO variable conversion.
The same applies to SV_DispatchThreadID and SV_GroupThreadID.
Fixes: #1371
Set type to r-value resulting from indexing vector, to prevent
float->uint conversion when source is already uint. Resulting
OpConvertFToU would otherwise fail validation because source is
already uint.
For LoadN, incorrect uint->float->uint can be avoided; fixing
potential truncation of big integer values.
This continues to prevent writing output buffers (out from a function),
but fixes the problem where the copy-in/out was not getting done.
Making everything work will require knowing both in/out-ness and bufferness,
but these are currently mutually exclusive, because both are storage
qualifiers.
Also, remove assumption that if something is opaque that it
must be in the UniformConstant storage class.
This allows function declarations to know all parameters will
be in the Function storage class.
Byte address buffers were failing to detect that they were byte address
buffers when used as fn parameters.
Note: this detection is a little awkward, and could be simplified if
it was easy to obtain the declared builtin type for an object.
