Note that we still have to preempt the propagation to SM1 pixel shader
uniforms. Otherwise this will turn the many constant derefs that appear
from the <index-val> copy generated in lower_index_loads() into a single
non-constant deref, causing it to allocate all the registers instead of
up until the last one used.
Some SM1 src registers have idx_count = 0, in which case we have to
respect that instead of always reading reg->reg.idx[0].offset even when
it is invalid.
Here, a vertex shader version of the previous test by Shaun is
introduced. Note that in this case the uniform allocates all 4 registers
instead of 3 because it is indirectly addressed.
Note that, for indexes with a decimal part, the behavior is different
depending on whether it is a temp load or a direct uniform load (which
can only happen on vertex shaders). The former rounds to the
closest-to-zero, while the latter rounds to the nearest even.
On MoltenVK it seems that all draws are always executed,
independently of the early depth stencil test. The problem doesn't
seem to belong to vkd3d or MoltenVK, because the generated Metal
commands look correct. I tried looking at a GPU capture with Xcode,
which was not very conclusive because it doesn't state clearly
whether early fragment tests were passed or not. Sometimes it
says that a fragment shader execution had no thread execution
data, which I interpret as the early fragment tests having
prevented the fragment shader from running, but it's not really
consistent, and it's never clear which results are based on
software simulation and which on the hardware run.
However taking everything into account I think the most likely
explanation is some incorrect optimization at the Metal level.
The graphics pipeline triggers an internal error in the Metal
pipeline compiler, with a completely generic error message. I have
no idea what the actual problem is.
This makes it more similar to the MSL and GLSL generators. It also looks
like a cleaner design, the backend is supposed to get access to the vsir
program after it has gone through the pipeline.
