It's currently useless, when there is a failure we drop out of
sm6_parser_function_init() before even checking what the current
instruction or value looks like.
They do not represent the raw Vulkan resource limits, but the
emulated d3d12 limits depending on the Vulkan limits. Therefore
name them according to d3d12.
I think the main argument for preallocating instructions and
passing them to helpers is that this simplifies error handling.
However it seems that the simplification is close to negligible,
while the current solution makes it harder to use the iterator
abstraction layer for the instruction array, and it also makes
the code harder to read and check.
It's main advantage over vkd3d_shader_message_context_copy_messages() is
that it can't fail. The original issue this addresses is that
vkd3d_shader_compile() should free its output when
vkd3d_shader_message_context_copy_messages() fails, as spotted by
Giovanni; that likely would have applied to a number of the other uses
of vkd3d_shader_message_context_copy_messages() as well.
Loads of components of vectors (i.e. functionally a subset of SWIZZLE
instructions, but expressed using LOAD) are legal, and generated elsewhere.
Due to circumstances they never reach this point currently, but we shouldn't use
vkd3d_unreachable() here.
