I wanted to kick-off discussion on how to support floating point precision qualifiers in NIR. This is purely on optimization for GLES where one can reduce the number of GPU cycles. At the moment the compiler discards the qualifiers early when abstract syntax tree (AST) is transformed into intermediate presentation (IR).
Iago added the initial support to IR in order to check that the stages agree on the precision. Naturally I started by rebasing his work on master (I dropped the actual checking part as it didn't automatically fit into master). I realized that it isn't sufficient to have the precision tracked in ir_variable alone. When the IR is further translated into NIR the precision is needed in ir_rvalue as well when NIR decides which opcode to use. Iago's patch isn't needed for the solution here afterall, I just included it to for context sake. Now, there are number of implementation alternatives, I think, both in AST/IR as well is in NIR. I thought I play with one approach to provide something "real" to aid the decision making regarding the architecture. I thought that despite fp16 (medium precision float) isn't really a proper type in glsl, it would clearer if it were one internally in the compiler though. I kept thinking fp64 and how I would introduce that into NIR. The first step was to do pretty much the same as what Dave Airlie did for doubles (fp64) in the compiler frontend. Then in NIR I decided to introduce new opcodes for half floats instead of modifying the existing float instructions to carry additional information about the precision. I would guess that there are drivers that are not really interested on this and hence we should means for the drivers to tell if the precision is to be taken into account or not. One natural place would be in patch number nine. This is just one example of details missing in the proposal - these patches are only meant to give a rough idea how the approach chosen would look like. Iago Toral Quiroga (1): glsl: Add tracking for GLSL precision qualifiers Topi Pohjolainen (15): glsl: Add half float type mesa: Add half float uniform support glsl: Add half float type generation glsl: Allow half float type to be used where-ever float is supported glsl: Add support for half floats in optimization passes glsl: Add ubo lowering support for half floats glsl: Add support for half float loop control glsl/ast: Use half float type for medium and low precisions nir: Introduce half float opcodes nir: Consider float precision when deciding between int/float nir: Consider float precision when deciding between int/float: part2 nir: Consider float precision when deciding between uint/int/float nir: Consider float precision when deciding between uint/float nir: Consider float precision when deciding opcode nir: Consider float precision when deciding opcode: part 2 src/glsl/ast_to_hir.cpp | 29 ++- src/glsl/builtin_type_macros.h | 16 ++ src/glsl/builtin_types.cpp | 31 +++ src/glsl/glsl_types.cpp | 50 ++++- src/glsl/glsl_types.h | 29 ++- src/glsl/ir.h | 13 ++ src/glsl/ir_clone.cpp | 1 + src/glsl/ir_print_visitor.cpp | 1 + src/glsl/ir_validate.cpp | 36 ++-- src/glsl/link_uniform_initializers.cpp | 2 + src/glsl/loop_controls.cpp | 1 + src/glsl/lower_ubo_reference.cpp | 12 +- src/glsl/nir/glsl_to_nir.cpp | 258 +++++++++++-------------- src/glsl/nir/nir.h | 2 + src/glsl/nir/nir_constant_expressions.py | 8 +- src/glsl/nir/nir_lower_io.c | 1 + src/glsl/nir/nir_opcodes.py | 78 +++++++- src/glsl/opt_algebraic.cpp | 11 +- src/glsl/opt_constant_propagation.cpp | 1 + src/glsl/opt_minmax.cpp | 2 + src/mesa/drivers/dri/i965/brw_fs.cpp | 1 + src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 1 + src/mesa/drivers/dri/i965/brw_shader.cpp | 1 + src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp | 1 + src/mesa/main/uniform_query.cpp | 5 +- src/mesa/program/ir_to_mesa.cpp | 3 + 26 files changed, 413 insertions(+), 181 deletions(-) -- 1.9.3 _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
