Hi all,
I thought I'd provide a quick status overview of the radeonsi NIR
backend. I'll attempt to list all outstanding tasks (that I'm aware of)
so if you are interested in working on one of those just give me a heads
up so we don't overlap.
Also feel free to reply with any feedback on performance and regression
results for games (see below). Although try to avoid games like DoW3
that make use of bindless textures until the missing support lands.
--------------------------
Test Suites / Conformance:
--------------------------
We are starting to look really good here. I don't have recent CTS
results bug it was similar low number of regressions.
Piglit results for TGSI on Polaris:
skip: 1555, pass: 24313, warn: 13, fail: 167, crash: 1
Piglit results for NIR on Polaris:
skip: 1555, pass: 24252, warn: 15, fail: 215, crash: 12
Summary of these 61 regressions:
arb_texture_multisample texelfetch bug(s)?
Number of failures: 39
Cause of failures: Unknown. Probably all the same bug, thus
far I have been unable to spot the issue. Feel free to
debug this :P
Status: Not started
Tests:
arb_texture_multisample
Missing bindless texture support
Number of failures: 7
Cause of failures: Mostly known
Status: In progress
Tests:
arb_bindless_texture
Bug in sampler lowering
Number of failures: 1
Cause of failures:
nir_lower_samplers_as_deref() only works when
a struct only contains samplers and is therefor no longer used
after lowering. If however the struct also contains ordinary
variables then we need to update its glsl_type after lowering
to remove the sampler members.
Status: Not started
Tests:
./bin/shader_runner
tests/spec/arb_arrays_of_arrays/execution/sampler/vs-struct-nonconst-non-opaque-members.shader_test
-auto -fbo
arb_enhanced_layouts component offsets bugs
Number of failures: 6
Cause of failures: Incorrect component offsets
Status: Not started
Tests: arb_enhanced_layouts/execution/component-layout
Missing NIR/NIR->LLVM support for frexp opcode
Number of failures: 1
Cause of failures: missing frexp opcode
Status: Not started
Tests:
./bin/shader_runner
tests/spec/arb_gpu_shader_fp64/execution/built-in-functions/fs-frexp-dvec4.shader_test
-auto -fbo
arb_tessellation_shader doubles bugs:
Number of failures: 3
Cause of failures: possibly dual slot varying related.
Status: Not started
Tests:
arb_tessellation_shader
Bug with explicit location for doubles
Number of failures: 1
Cause of failures: incorrect location offset?
Status: Not started
Tests:
./bin/shader_runner
tests/spec/arb_gpu_shader_fp64/execution/explicit-location-gs-fs-vs.shader_test
-auto -fbo
Shared atomics bug
Number of failures: 1
Cause of failures: Unknown
Status: Not started
Tests:
./bin/shader_runner
tests/spec/arb_compute_shader/execution/shared-atomics.shader_test -auto
-fbo
Non optimal variable indexing:
Number of failures: 1
Cause of failures: Excessive spilling. Optimisations to the
nir -> llvm path should resolve the issue (see the missing
optimisations section below).
Status: Not started
Tests:
./bin/shader_runner
tests/spec/glsl-1.50/execution/variable-indexing/gs-input-array-vec3-index-rd.shader_test
-auto -fbo
gs max input components bug
Number of failures: 1
Cause of failures: Possibly related to the issue above.
Status: Not started
Tests:
./bin/shader_runner
tests/spec/glsl-1.50/execution/geometry/max-input-components.shader_test
-auto -fbo
--------------------------
Missing optimisations:
--------------------------
- There are a number of TODOS in si_shader_nir.c that need to be
finished off.
- Optimal variable indexing (see Non optimal variable indexing in
the piglit failures above). Need to implement something in nir -> llvm
like si_llvm_emit_fetch() does for TGSI. This will benefit both
radeonsi and radv.
- Fast path when user data SGPRs point to constant buffer 0 directly.
See si_shader.c:fetch_constant()
- Need to double check NIR is not lowering anything we can handle
natively.
- There are likely more improvements we can do for the NIR shader cache.
For one we should probably create a driver function so that we can
call all NIR opts/lowering from the st at link time to avoid variants
having to call these for a second time.
- Likely a bunch more I've forgotten or missed.
-----------------
Performance:
-----------------
More testing is needed. I haven't done much testing here yet, there were
some phoronix tests a while back that showed a few regressions in
performance. However at that stage we didn't yet have any shader cache
and the large MadMax regression was actually causes by an llvm bug
(which has been fixed in master 7.0). I'm hopeful any regressions won't
be too bad at this stage.
-----------------------------
Real world testing (Games):
-----------------------------
Again more testing is needed here. Of the few games I've tested so far
most seem to run fine.
Known regressions:
- Dead Island (displays only graphics corruptions on start-up)
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