This set of code changes are for stencil code generation
support. Both one-sided and two-sided stenciling are supported.
In addition to the raw code generation changes, these changes had
to be made elsewhere in the system:
- Added new "register set" feature to the SPE assembly generation.
A "register set" is a way to allocate multiple registers and free
them all at the same time, delegating register allocation management
to the spe_function unit. It's quite useful in complex register
allocation schemes (like stenciling).
- Added and improved SPE macro calculations.
These are operations between registers and unsigned integer
immediates. In many cases, the calculation can be performed
with a single instruction; the macros will generate the
single instruction if possible, or generate a register load
and register-to-register operation if not. These macro
functions are: spe_load_uint() (which has new ways to
load a value in a single instruction), spe_and_uint(),
spe_xor_uint(), spe_compare_equal_uint(), and spe_compare_greater_uint().
- Added facing to fragment generation. While rendering, the rasterizer
needs to be able to determine front- and back-facing fragments, in order
to correctly apply two-sided stencil. That requires these changes:
- Added front_winding field to the cell_command_render block, so that
the state tracker could communicate to the rasterizer what it
considered to be the front-facing direction.
- Added fragment facing as an input to the fragment function.
- Calculated facing is passed during emit_quad().
- Use a lookup table for log2.
- Compute (float) (1 << ipart) by tweaking with the exponent directly to
avoid integer overflow and float conversion.
- Also table negative exponents to avoid float division and branching.
- Implement util_fast_exp as function of util_fast_exp2.
Special care must be taken when calling compiler generated SSE2 functions
from the runtime generated SSE2: saving the xmm registers, and notify gcc
the stack is not 16byte aligned.
It would be more efficient to keep the stack pointer 16byte aligned, but
too hairy, and not consistent in all x86 architectures.
This has been tested in linux x86 and windows x86 userspace. Not tested on
x86-64 because it is broken for other reasons (even without this change).
Will be used for instructions like SIN/COS/POW/TEX/etc. The PPU needs to
know the address of some functions in the SPU address space. Send that
info to the PPU/main memory rather than patch up shaders on the SPU side.
Not finished/tested yet...
Defaults for program length, num ALU instructions, num indirections, etc.
basically indicate no limit for software rendering. Driver should override
as needed.
Stephane Marchesin