With these changes, the tests/stencil_twoside test now works.
- Eliminate blending from the stencil_twoside test, as it produces an
unneeded dependency on having blending working
- The spe_splat() function will now work if the register being splatted
and the destination register are the same
- Separate fragment code generated for front-facing and back-facing
fragments. Often these are the same; if two-sided stenciling is on,
they can be different. This is easier and faster than generating
code that does both tests and merges the results.
- Fixed a cut/paste bug where if the back Z-pass stencil operation
were different from all the other operations, the back Z-fail
results were incorrect.
Two definitive bugs in stenciling were fixed.
The first, reversed registers in the generated Select Bytes (selb)
instruction, caused the stenciling INCR and DECR operations to
fail dramatically, putting new values in where old values were
supposed to be and vice versa.
The second caused stencil tiles to not be read and written from
main memory by the SPUs. A per-spu flag, spu.read_depth, was used
to indicate whether the SPU should be reading depth tiles, and was set
only when depth was enabled. A second flag, spu.read_stencil, was
set when stenciling was enabled, but never referenced.
As stenciling and depth are in the same tiles on the Cell, and there
is no corresponding TAG_WRITE_TILE_STENCIL to complement
TAG_WRITE_TILE_COLOR and TAG_WRITE_TILE_Z, I fixed this by
eliminating the unused "spu.read_stencil", renaming "spu.read_depth"
to "spu.read_depth_stencil", and setting it if either stenciling or
depth is enabled.
I also added an optimization to the fragment ops generation code,
that avoids calculating stencil values and/or stencil writemask
when the stencil operations are all KEEP.
