Ilia noticed that my lowering pass was converting the constant array
used by textureGatherOffsets' offsets parameter to a uniform. This
broke textureGather for Nouveau, and is generally a horrible plan,
since it violates the GLSL constraint that offsets must be an
immediate constant.
When I wrote this pass, I neglected to consider whole array assignment.
I figured opt_array_splitting would handle constant indexing, so this
pass was really about fixing variable indexing.
textureGatherOffsets is an example of whole array access that we really
don't want to touch. Whole array copies don't appear to benefit from
this either - they're most likely initializers for temporary arrays
which are going to be mutated anyway. Since you're copying, you may
as well copy from immediates, not uniforms.
This patch makes the pass look for ir_dereference_arrays of
ir_constants, rather than looking for any ir_constant directly.
This way, it ignores whole array assignment.
No shader-db changes or Piglit regressions on Haswell. Some Piglit
tests generate different code (fixing textureGatherOffsets on Nouveau).
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Tested-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Cc: "10.4" <mesa-stable@lists.freedesktop.org>
Uniform names (even for hidden uniforms) are required to be unique; some
parts of the compiler assume they can be looked up by name.
Fixes the piglit test: tests/spec/glsl-1.20/linker/array-initializers-1
Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Cc: "10.4" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Consider GLSL code such as:
const ivec2 offsets[] =
ivec2[](ivec2(-1, -1), ivec2(-1, 0), ivec2(-1, 1),
ivec2(0, -1), ivec2(0, 0), ivec2(0, 1),
ivec2(1, -1), ivec2(1, 0), ivec2(1, 1));
ivec2 offset = offsets[<non-constant expression>];
Both i965 and nv50 currently handle this very poorly. On i965, this
becomes a pile of MOVs to load the immediate constants into registers,
a pile of scratch writes to move the whole array to memory, and one
scratch read to actually access the value - effectively the same as if
it were a non-constant array.
We'd much rather upload large blocks of constant data as uniform data,
so drivers can simply upload the data via constbufs, and not have to
populate it via shader instructions.
This is currently non-optional because both i965 and nouveau benefit
from it, and according to Marek radeonsi would benefit today as well.
(According to Tom, radeonsi may want to handle this itself in the long
term, but we can always add a flag when it becomes useful.)
Improves performance in a terrain rendering microbenchmark by about 2x,
and cuts the number of instructions in about half. Helps a lot of
"Natural Selection 2" shaders, as well as one "HOARD" shader.
total instructions in shared programs: 5473459 -> 5471765 (-0.03%)
instructions in affected programs: 5880 -> 4186 (-28.81%)
v2: Use ir_var_hidden to avoid exposing the new uniform via the GL
uniform introspection API.
v3: Alphabetize Makefile.sources properly.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77957
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
