On Fri, May 15, 2015 at 5:39 AM, Topi Pohjolainen <topi.pohjolai...@intel.com> wrote: > 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.
jfwiw, I can[*] in a lot of cases have precision per operand.. for example, add a f32 + f16 with result into f32. So having separate opcodes seems kind of funny. [*] as far as I can tell.. but admittedly I haven't had any reason yet to spend time r/e'ing half-precision stuff for adreno BR, -R > 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 _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
