[Mesa-dev] [PATCH 00/31] nir: Use a 1-bit data type for booleans
Jason Ekstrand
jason at jlekstrand.net
Sun Nov 4 04:21:20 UTC 2018
Thanks! I don't mean to be a pest. However, not everyone is as good about
keeping track of their backlog as you are so I thought it might be worth a
reminder.
--Jason
On Sat, Nov 3, 2018 at 7:59 PM Ian Romanick <idr at freedesktop.org> wrote:
> I haven't forgotten... I'm planning to dig into this next week.
>
> On 11/02/2018 06:42 AM, Jason Ekstrand wrote:
> > Bump
> >
> > On Mon, Oct 22, 2018 at 5:14 PM Jason Ekstrand <jason at jlekstrand.net
> > <mailto:jason at jlekstrand.net>> wrote:
> >
> > This is something that Connor and I have talked about quite a bit
> > over the
> > last couple of months. The core idea is to replace NIR's current
> 32-bit
> > 0/-1 D3D10-style booleans with a 1-bit data type. All in all, I
> > think it
> > worked out pretty well though I really don't like the proliferation
> of
> > 32-bit comparison opcodes we now have kicking around for i965.
> >
> > Why? No hardware really has a 1-bit type, right? Well, sort of...
> AMD
> > actually uses 64-bit scalars for booleans with one bit per
> invocation.
> > However, most hardware such as Intel uses some other larger value for
> > booleans. The real benefit of 1-bit booleans and requiring a
> > lowering pass
> > is that you can do somewhat custom lowering (like AMD wants) and your
> > lowering pass can always tell in an instant if a value is a boolean
> > based
> > on the bit size. As can be seen in the last patch, this makes it
> really
> > easy to implement a bool -> float lowering pass for hardware that
> > doesn't
> > have real integers where NIR's current booleans are actually rather
> > painful.
> >
> > On Intel, the situation is a bit more complicated. It's tempting to
> say
> > that we have 32-bit D3D10 booleans. However, they're not really
> D3D10
> > booleans on gen4-5 because the top 31 bits are undefined garbage
> > and, while
> > iand, ior, ixor, and inot operations work, you have to iand with 1
> > at the
> > last minute to clear off all that garbage. Also, on all
> generations, a
> > comparison of two N-bit values results in an N-bit boolean, not a
> 32-bit
> > bool. This has caused the Igalia folks no end of trouble as they've
> > been
> > working on native 8 and 16-bit support. If, instead, we have a
> > 1-bit bool
> > with a lowering pass and we can lower to whatever we want, then we
> could
> > lower to a set of comparison opcodes that return the same bit-size
> > as they
> > compare and it would match GEN hardware much better.
> >
> > But what about performance? Aren't there all sorts of neat tricks
> > we can
> > do with D3D10 booleans like b & 1.0f for b2f? As it turns out, not
> > really;
> > that's about the only one. There is some small advantage when
> > optimizing
> > shaders that come from D3D if your native representation of booleans
> > matches that of D3D. However, penultimate patch in this series adds
> > a few
> > small optimizations that get us to actually better than we were
> before.
> > With the entire series, shader-db on Kaby Lak looks like this:
> >
> > total instructions in shared programs: 15084098 -> 14988578
> (-0.63%)
> > instructions in affected programs: 1321114 -> 1225594 (-7.23%)
> > helped: 2340
> > HURT: 23
> >
> > total cycles in shared programs: 369790134 -> 359798399 (-2.70%)
> > cycles in affected programs: 134085452 -> 124093717 (-7.45%)
> > helped: 2149
> > HURT: 720
> >
> > total loops in shared programs: 4393 -> 4393 (0.00%)
> > loops in affected programs: 0 -> 0
> > helped: 0
> > HURT: 0
> >
> > total spills in shared programs: 10158 -> 10051 (-1.05%)
> > spills in affected programs: 1429 -> 1322 (-7.49%)
> > helped: 8
> > HURT: 15
> >
> > total fills in shared programs: 22105 -> 21720 (-1.74%)
> > fills in affected programs: 2853 -> 2468 (-13.49%)
> > helped: 12
> > HURT: 15
> >
> > How about ease of use? Are they a pain to deal with? Yes, adding
> > support
> > for 1-bit types was a bit awkward in a few places but most of it was
> > dealing with all the places where we have 32-bit booleans baked into
> > assumptions. Getting rid of that baking in solves the problem and
> also
> > makes the whole IR more future-proof.
> >
> > All in all, I'd say I'm pretty happy with it. However, I'd like
> other
> > people (particularly the AMD folks) to play with it a bit and verify
> > that
> > it solves their problems as well. Also, I added a lowering pass and
> > tried
> > to turn it on in everyone's driver but may not have put it in the
> right
> > spot. Please double-check my work. For those wishing to take a
> > look, you
> > can also find the entire series on my gitlab here:
> >
> >
> https://gitlab.freedesktop.org/jekstrand/mesa/commits/review/nir-1-bit-bool
> >
> > Please review!
> >
> > --Jason
> >
> > Cc: Connor Abbott <cwabbott0 at gmail.com <mailto:cwabbott0 at gmail.com>>
> > Cc: Timothy Arceri <tarceri at itsqueeze.com
> > <mailto:tarceri at itsqueeze.com>>
> > Cc: Eric Anholt <eric at anholt.net <mailto:eric at anholt.net>>
> > Cc: Rob Clark <robdclark at gmail.com <mailto:robdclark at gmail.com>>
> > Cc: Karol Herbst <karolherbst at gmail.com <mailto:
> karolherbst at gmail.com>>
> > Cc: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl
> > <mailto:bas at basnieuwenhuizen.nl>>
> > Cc: Alyssa Rosenzweig <alyssa at rosenzweig.io
> > <mailto:alyssa at rosenzweig.io>>
> >
> >
> > Jason Ekstrand (31):
> > nir/validate: Print when the validation failed
> > nir/constant_folding: Add an unreachable to a switch
> > nir/constant_folding: Use nir_src_as_bool for discard_if
> > nir/builder: Add a nir_imm_true/false helpers
> > nir/builder: Handle 16-bit floats in nir_imm_floatN_t
> > nir/search: Use nir_builder
> > nir/opt_if: Rework condition propagation
> > nir/system_values: Use the bit size from the load_deref
> > glsl/nir: Use i2b instead of ine for fixing UBO/SSBO booleans
> > nir/prog: Use nir_bany in kill handling
> > spirv: Use the right bit-size for spec constant ops
> > spirv: Initialize subgroup destinations with the destination type
> > intel/nir: Use the OPT macro for more passes
> > nir/algebraic: Disable b2f lowering and two optimizations
> > nir: Rename boolean-related opcodes to include 32 in the name
> > FIXUP: nir/builder: Generate 32-bit bool opcodes transparently
> > FIXUP: nir/algebraic: Remap boolean opcodes to the 32-bit variant
> > FIXUP: Use 32-bit opcodes in the NIR producers and optimizations
> > FIXUP: Use 32-bit opcodes in the NIR back-ends
> > nir/constant_expressions: Rework boolean handling
> > nir: Add support for 1-bit data types
> > nir: Add 1-bit boolean opcodes
> > nir: Add a bool to int32 lowering pass
> > glsl,spirv: Generate 1-bit booleans
> > FIXUP: Revert "Use 32-bit opcodes in the NIR producers and
> > optimizations"
> > FIXUP: Revert "nir/builder: Generate 32-bit bool opcodes
> > transparently"
> > FIXUP: nir/builder: Generate 1-bit booleans in nir_build_imm_bool
> > nir/algebraic: Optimize 1-bit booleans
> > nir/algebraic: Add back lower_b2f and a b2f optimization
> > nir/algebraic: Add some optimizations for D3D-style booleans
> > nir: Add a bool to float32 lowering pass
> >
> > src/amd/common/ac_nir_to_llvm.c | 30 +--
> > src/amd/vulkan/radv_shader.c | 6 +-
> > src/broadcom/compiler/nir_to_vir.c | 44 ++---
> > src/broadcom/compiler/vir.c | 2 +
> > src/compiler/Makefile.sources | 2 +
> > src/compiler/glsl/glsl_to_nir.cpp | 28 +--
> > src/compiler/nir/meson.build | 2 +
> > src/compiler/nir/nir.c | 15 +-
> > src/compiler/nir/nir.h | 36 ++--
> > src/compiler/nir/nir_algebraic.py | 22 ++-
> > src/compiler/nir/nir_builder.h | 51 ++++-
> > src/compiler/nir/nir_constant_expressions.py | 53 ++---
> > src/compiler/nir/nir_instr_set.c | 23 ++-
> > src/compiler/nir/nir_lower_alu_to_scalar.c | 4 +
> > src/compiler/nir/nir_lower_bool_to_float.c | 181
> ++++++++++++++++++
> > src/compiler/nir/nir_lower_bool_to_int32.c | 162 ++++++++++++++++
> > src/compiler/nir/nir_lower_int64.c | 2 +-
> > .../nir/nir_lower_load_const_to_scalar.c | 3 +
> > src/compiler/nir/nir_lower_returns.c | 4 +-
> > src/compiler/nir/nir_lower_subgroups.c | 2 +-
> > src/compiler/nir/nir_lower_system_values.c | 1 +
> > src/compiler/nir/nir_opcodes.py | 31 ++-
> > src/compiler/nir/nir_opt_algebraic.py | 19 +-
> > src/compiler/nir/nir_opt_constant_folding.c | 18 +-
> > src/compiler/nir/nir_opt_if.c | 91 +++------
> > src/compiler/nir/nir_opt_intrinsics.c | 2 +-
> > src/compiler/nir/nir_opt_large_constants.c | 5 +
> > src/compiler/nir/nir_print.c | 3 +
> > src/compiler/nir/nir_search.c | 112 +++--------
> > src/compiler/nir/nir_search.h | 9 +-
> > src/compiler/nir/nir_validate.c | 16 +-
> > src/compiler/nir/tests/vars_tests.cpp | 38 ++--
> > src/compiler/nir_types.cpp | 2 +-
> > src/compiler/nir_types.h | 4 +-
> > src/compiler/spirv/spirv_to_nir.c | 23 ++-
> > src/compiler/spirv/vtn_alu.c | 4 +-
> > src/compiler/spirv/vtn_cfg.c | 10 +-
> > src/compiler/spirv/vtn_subgroup.c | 12 +-
> > src/gallium/auxiliary/nir/tgsi_to_nir.c | 20 +-
> > .../drivers/freedreno/ir3/ir3_compiler_nir.c | 31 +--
> > src/gallium/drivers/radeonsi/si_shader_nir.c | 2 +
> > src/gallium/drivers/vc4/vc4_program.c | 50 ++---
> > src/intel/compiler/brw_fs_nir.cpp | 80 ++++----
> > src/intel/compiler/brw_nir.c | 16 +-
> > .../brw_nir_analyze_boolean_resolves.c | 24 +--
> > .../compiler/brw_nir_lower_image_load_store.c | 2 +-
> > src/intel/compiler/brw_vec4_nir.cpp | 122 ++++++------
> > src/intel/vulkan/anv_pipeline.c | 2 +-
> > src/mesa/drivers/dri/i965/brw_program.c | 4 +-
> > src/mesa/main/glspirv.c | 2 +-
> > src/mesa/program/prog_to_nir.c | 2 +-
> > src/mesa/state_tracker/st_glsl_to_nir.cpp | 2 +-
> > 52 files changed, 934 insertions(+), 497 deletions(-)
> > create mode 100644 src/compiler/nir/nir_lower_bool_to_float.c
> > create mode 100644 src/compiler/nir/nir_lower_bool_to_int32.c
> >
> > --
> > 2.19.1
> >
> >
> >
> > _______________________________________________
> > mesa-dev mailing list
> > mesa-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> >
>
>
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