It's a complicated story. But from what I can tell, in GL compute
without barriers, the blob is able to redistribute the workgroups in
various ways (that are not yet understood), whereas with barriers it
cannot redistribute anything, which accounts for erratic workgroup
packing without barriers.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3835>
At this point this simply involves fixing the initialization of the
sample mask flag register to take the right dispatch mask from the
thread payload, and fixing sample_mask_reg() to return f1.1 for the
second half of a SIMD32 thread. This improves Manhattan 3.1
performance by 2.4%±0.31% (N>40) on my ICL with SIMD32 enabled
relative to falling back to SIMD16 for the shaders that use discard.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
In SIMD32 programs that don't use discard, the upper 16 bits of the UD
result of sample_mask_reg() don't contain the sample mask of the upper
16 channels as one would expect. Stop pretending we are returning a
valid 32-bit mask.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
FIND_LIVE_CHANNEL was using f1.0-f1.1 as temporary flag register on
Gen7, instead use f0.0-f0.1. In order to avoid collision with the
discard sample mask, move the latter to f1.0-f1.1. This makes room
for keeping track of the sample mask of the second half of SIMD32
programs that use discard.
Note that some MOVs of the sample mask into f1.0 become redundant now
in lower_surface_logical_send() and lower_a64_logical_send().
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>x
Use it instead of hard-coding f0.1 for the sample mask of programs
that use discard. This will make the task easier when we replace f0.1
with another flag register location in order to support discard with
SIMD32 shaders.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
It's only really useful there. This will avoid confusion with another
helper with a similar purpose I'm about to introduce that will be
useful in multiple files from the FS back-end.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
The SIMD8 dual-source blending framebuffer write messages seem to have
trouble releasing the pixel scoreboard dependency in SIMD32 dispatch
mode, which leads to hangs. I have a better workaround for this which
doesn't involve disabling SIMD32 when dual-source blending is enabled,
but I'm still investigating some issues with it. Limit the dispatch
width to SIMD16 in such cases for the moment in order to make the CI
happy on ICL with SIMD32 fragment shaders enabled.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Currently the "Source0 Alpha Present to RenderTarget" bit of the RT
write message header is derived from brw_wm_prog_data::replicate_alpha.
However the src0_alpha payload is provided anytime it's specified to
the logical message. This could theoretically lead to an
inconsistency if somebody provided a src0_alpha value while
brw_wm_prog_data::replicate_alpha was false, as I'm planning to do in
a future commit in order to implement a hardware workaround.
Instead calculate the header bit based on whether a src0_alpha value
was provided to the logical message, which guarantees the same
behavior on pre-ICL and ICL+ (the latter used an extended descriptor
bit for this which didn't suffer from the same issue). Remove the
brw_wm_prog_data::replicate_alpha flag.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Together with the fixup_nomask_control_flow() pass introduced in a
previous patch, this implements a less invasive alternative to the
workaround documented in the hardware spec for GEN:BUG:1407528679,
which doesn't involve disabling structured control flow.
Under some conditions Gen12 hardware can end up executing a BB with
all channels disabled, which will lead to the execution of any NoMask
instructions in it, even though any execution-masked instructions will
be correctly shot down. This could break assumptions of the SWSB pass
if the data computed by a NoMask instruction is synchronized against
by using an SWSB annotation baked into a regular execution-masked
instruction, since the first (NoMask) instruction may be executed
redundantly by the hardware, even though the second will correctly be
shot down, potentially leading to a RaW or WaW hazard if a third
instruction subsequently accesses the destination register of the
first instruction.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Cc: 20.0 <mesa-stable@lists.freedesktop.org>
Found by inspection. Existing code was trying to avoid assuming that
an SBID had been assigned to the virtual instruction, but
synchronizing the header setup with respect to the previous SIMD16
SEND by using SYNC.ALLRD doesn't really seem possible unless the SEND
instruction had been assigned an SBID. Assert-fail instead if no SBID
has been allocated.
Fixes: 15e3a0d9d2 "intel/eu/gen12: Set SWSB annotations in hand-crafted assembly."
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Cc: 20.0 <mesa-stable@lists.freedesktop.org>
This is a less invasive alternative to the workaround documented in
the hardware spec for GEN:BUG:1407528679, which doesn't involve
disabling structured control flow (it's unlikely that switching to
GOTO/JOIN would have actually fixed the problem anyway).
Under some conditions Gen12 hardware can end up executing a BB with
all channels disabled, which will lead to the execution of any NoMask
instructions in it, even though any execution-masked instructions will
be correctly shot down. This may break assumptions of some NoMask
SEND messages whose descriptor depends on data generated by live
invocations of the shader.
This avoids the problem by predicating certain instructions on an ANY
horizontal predicate that makes sure that their execution is omitted
when all channels of the program are disabled. The shader-db impact
of this patch seems to be minimal:
total instructions in shared programs: 17169833 -> 17169913 (0.00%)
instructions in affected programs: 30663 -> 30743 (0.26%)
helped: 0
HURT: 42
total cycles in shared programs: 336966176 -> 336968568 (0.00%)
cycles in affected programs: 2367290 -> 2369682 (0.10%)
helped: 0
HURT: 13
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Cc: 20.0 <mesa-stable@lists.freedesktop.org>
We need to pass a width of 32 since the opcode bashes the whole f1.0
register on IVB. This is unlikely to have caused problems since f1.0
is largely unused currently. That's likely to change soon though,
even on platforms other than Gen7.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Cc: 20.0 <mesa-stable@lists.freedesktop.org>
Found by inspection. This seems particularly likely to cause problems
with instructions dependent on the current execution mask like
SHADER_OPCODE_FIND_LIVE_CHANNEL or the FS_OPCODE_LOAD_LIVE_CHANNELS
instruction I'm about to introduce, but one could imagine it leading
to data corruption if CSE ever managed to combine two instructions
before and after the FS_OPCODE_PLACEHOLDER_HALT, since the one before
may not be executed for some channels.
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Cc: 20.0 <mesa-stable@lists.freedesktop.org>
Alyssa Rosenzweig