We can achieve most of what brw_fs_opt_predicated_break() does with
simple peepholes at NIR -> BRW conversion time.
For predicated break and continue, we can simply look at an IF ... ENDIF
sequence after emitting it. If there's a single instruction between the
two, and it's a BREAK or CONTINUE, then we can move the predicate from
the IF onto the jump, and delete the IF/ENDIF. Because we haven't built
the CFG at this stage, we only need to remove them from the linked list
of instructions, which is trivial to do.
For the predicated while optimization, we can rely on the fact that we
already did the predicated break optimization, and simply look for a
predicated BREAK just before the WHILE. If so, we move the predicate
onto the WHILE, invert it, and remove the BREAK.
There are a few cases where this approach does a worse job than the old
one: nir_convert_from_ssa may introduce load_reg and store_reg in blocks
containing break, and nir_trivialize_registers may decide it needs to
insert movs into those blocks. So, at NIR -> BRW time, we'll actually
emit some MOVs there, which might have been possible to copy propagate
out after later optimizations.
However, the fossil-db results show that it's still pretty competitive.
For instructions, 1017 shaders were helped (average -1.87 instructions),
while only 62 were hurt (average +2.19 instructions). In affected
shaders, it was -0.08% for instructions.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30498>
We don't actually need to extend g0's live range to the EOT message
generally - most messages that end a shader are headerless. The main
implicit use of g0 is for constructing scratch headers. With the last
two patches, we now consider scratch access that may exist in the IR
and already extend the liveness appropriately.
There is one remaining problem: spilling. The register allocator will
create new scratch messages when spilling a register, which need to
create scratch headers, which need g0. So, every new spill or fill
might extend the live range of g0, which would create new interference,
altering the graph. This can be problematic.
However, when compiling SIMD16 or SIMD32 fragment shaders, we don't
allow spilling anyway. So, why not use allow g0? Also, when trying
various scheduling modes, we first try allocation without spilling.
If it works, great, if not, we try a (hopefully) less aggressive
schedule, and only allow spilling on the lowest-pressure schedule.
So, even for regular SIMD8 shaders, we can potentially gain the use
of g0 on the first few tries at scheduling+allocation.
Once we try to allocate with spilling, we go back to reserving g0
for the entire program, so that we can construct scratch headers at
any point. We could possibly do better here, but this is simple and
reliable with some benefit.
Thanks to Ian Romanick for suggesting I try this approach.
fossil-db on Alchemist shows some more spill/fill improvements:
Totals:
Instrs: 149062395 -> 149053010 (-0.01%); split: -0.01%, +0.00%
Cycles: 12609496913 -> 12611652181 (+0.02%); split: -0.45%, +0.47%
Spill count: 52891 -> 52471 (-0.79%)
Fill count: 101599 -> 100818 (-0.77%)
Scratch Memory Size: 3292160 -> 3197952 (-2.86%)
Totals from 416541 (66.59% of 625484) affected shaders:
Instrs: 124058587 -> 124049202 (-0.01%); split: -0.01%, +0.01%
Cycles: 3567164271 -> 3569319539 (+0.06%); split: -1.61%, +1.67%
Spill count: 420 -> 0 (-inf%)
Fill count: 781 -> 0 (-inf%)
Scratch Memory Size: 94208 -> 0 (-inf%)
Witcher 3 shows a 33% reduction in scratch memory size, for example.
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30319>
The generator code for emitting legacy scratch headers was implicitly
using g0 as a source. But the IR wasn't indicating any usage of g0,
which means the liveness isn't properly tracked at the IR level.
It works because we reserve g0 as permanently live for the whole
program. In order to stop doing that, we need to record it properly.
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30319>
Indirect addressing(vx1 and vxh) not supported with UB/B datatype for
src0, so we need to change the data type for both dest and src0.
This fixes following tests cases on Xe2+
- dEQP-VK.spirv_assembly.instruction.compute.8bit_storage.push_constant_8_to_16*
- dEQP-VK.spirv_assembly.instruction.compute.8bit_storage.push_constant_8_to_32*
Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29316>
We can do CSEL on F, HF, *W, and *D on Gfx11+. Gfx9 can only do F.
We can lower unsupported types to CMP+CSEL, allowing us to use CSEL
in the IR and not worry about the limitations.
Rework: (Sagar)
- Update validation pass for CSEL
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29316>
This implements a replacement for the previous implementation of
nir_intrinsic_load_barycentric_at_offset that relied on the Pixel
Interpolator shared function, since it's going to be removed from the
hardware from Xe2 onwards.
That's okay since we can get all the primitive setup information
needed for interpolation at an arbitrary coordinate: We use the X/Y
offset relative to the "X/Y Start" coordinates from the thread payload
order to evaluate the plane equations also provided in the thread
payload for each barycentric coordinate of each polygon. The
evaluation of the barycentric plane equations (and the RHW plane
equation for perspective-correct interpolation) uses the accumulator
and MAD/MAC for ALU efficiency, but that means we need to manually
split instructions to fit the width of the accumulator. The division
and scaling for perspective-correct interpolation is also now done in
the shader if necessary.
Note that even though this is only immediately useful on Xe2+, the
thread payload numbers are filled out for older platforms, and the EU
restrictions of previous Xe platforms are taken into account, mostly
for the purposes of testing and performance evaluation.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29847>
This has a number of advantages compared to the pass I wrote years ago:
- It can easily perform either Global CSE or block-local CSE, without
needing to roll any dataflow analysis, thanks to SSA def analysis.
This global CSE is able to detect and coalesce memory loads across
blocks. Although it may increase spilling a little, the reduction
in memory loads seems to more than compensate.
- Because SSA guarantees that values are never written more than once,
the new CSE pass can directly reuse an existing value. The old pass
emitted copies at the point where it discovered a value because it
had no idea whether it'd be mutated later. This led it to generate
a ton of trash for copy propagation to clean up later, and also a
nasty fragility where CSE, register coalescing, and copy propagation
could all fight one another by generating and cleaning up copies,
leading to infinite optimization loops unless we were really careful.
Generating less trash improves our CPU efficiency.
- It uses hash tables like nir_instr_set and nir_opt_cse, instead of
linearly walking lists and comparing each element. This is much more
CPU efficient.
- It doesn't use liveness analysis, which is one of the most expensive
analysis passes that we have. Def analysis is cheaper.
In addition to CSE'ing SSA values, we continue to handle flag writes,
as this is a huge source of CSE'able values. These remain block local.
However, we can simply track the last flag write, rather than creating
entire sets of instruction entries like the old pass. Much simpler.
The only real downside to this pass is that, because the backend is
currently only partially SSA, it has limited visibility and isn't able
to see all values. However, the results appear to be good enough that
the new pass can effectively replace the old pass in almost all cases.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28666>
Like NIR, we print SSA defs as %1, %2, and so on. The number here is
the VGRF number. VGRFs that don't correspond to a SSA def remain
printed as vgrf1, vgrf2, and so on.
This makes it much easier to see what values are SSA and which aren't.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28666>
Even without a full use list, simply tracking the number of uses will
let us tell "this is the only use of the def" or "we've just replaced
all uses of a def". It's inexpensive to calculate and will be useful.
(rebased by Kenneth Graunke)
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28666>
This introduces a new analysis pass that opportunistically looks for
VGRFs which happen to satisfy the SSA definition properties.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28666>
Our code to initialize gl_SubgroupInvocation uses multiple instructions
some of which are partial writes. This makes it difficult to analyze
expressions involving gl_SubgroupInvocation, which appear very
frequently in compute shaders.
To make this easier, we add a new virtual opcode which initializes
a full VGRF to the value of gl_SubgroupInvocation. (We also expand
it to UD for SIMD8 so there are not partial write issues.) We then
lower it to the original code later on in compilation, after we've
done the bulk of our optimizations.
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28666>
Always select sample barycentric when persample dispatch is unknown at
compile time and let the payload adjustments feed the expected value
based on dispatch.
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: mesa-stable
Reviewed-by: Ivan Briano <ivan.briano@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27803>
Moves the lowering of VGRFs into FIXED_GRFs from the code generation
to (almost) right after the register allocation.
This will allow: (1) later passes not worry about VGRFs (and what they
mean in a post reg alloc phase) and (2) make easier to add certain
types of validation post reg alloc phase using the backend IR.
Note that a couple of passes still take advantage of seeing "allocated
VGRFs", so perform lowering after they run.
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28604>
We no longer support the old LINE+MAC lowering, and we already lower
this to MAD in NIR on Gfx11+, so the LINTERP virtual opcode always
corresponds the PLN. The only catch is that LINTERP's operands are
reversed from PLN, so we have to switch them.
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28705>
We already have a logical opcode and lower to what is basically a send
instruction. We just weren't using SHADER_OPCODE_SEND, instead having
extra redundant infrastructure for no real gain.
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28705>
We don't necessarily want to split up MOVs for 64-bit addresses into
2x 32-bit MOVs right away, as this makes things like copy propagating
the whole address around harder. We should do this late, once, while
still doing other algebraic optimizations earlier.
fossil-db results for Alchemist show tiny improvements:
Totals:
Instrs: 161310502 -> 161310436 (-0.00%); split: -0.00%, +0.00%
Cycles: 14370605606 -> 14370605159 (-0.00%); split: -0.00%, +0.00%
Totals from 33 (0.01% of 652298) affected shaders:
Instrs: 15053 -> 14987 (-0.44%); split: -0.64%, +0.20%
Cycles: 196947 -> 196500 (-0.23%); split: -0.25%, +0.02%
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28286>
Thanks to Ken for suggesting this URB refactoring change and pointing
out that the LSC can operate on the byte offset granularity.
This should fix the geometry shader test cases where we have more than
32 vertices since previously we were failing to write the correct
control data bits because of incorrect write mask.
Shader-db results for Xe2:
total instructions in shared programs: 153475 -> 153437 (-0.02%)
instructions in affected programs: 1374 -> 1336 (-2.77%)
helped: 11
HURT: 0
helped stats (abs) min: 3 max: 5 x̄: 3.45 x̃: 3
helped stats (rel) min: 1.67% max: 4.92% x̄: 3.23% x̃: 2.70%
95% mean confidence interval for instructions value: -3.92 -2.99
95% mean confidence interval for instructions %-change: -4.10% -2.36%
Instructions are helped.
total loops in shared programs: 140 -> 140 (0.00%)
loops in affected programs: 0 -> 0
helped: 0
HURT: 0
total cycles in shared programs: 16002649 -> 16002329 (<.01%)
cycles in affected programs: 9174 -> 8854 (-3.49%)
helped: 11
HURT: 0
helped stats (abs) min: 22 max: 38 x̄: 29.09 x̃: 32
helped stats (rel) min: 2.62% max: 5.54% x̄: 3.78% x̃: 3.85%
95% mean confidence interval for cycles value: -33.56 -24.62
95% mean confidence interval for cycles %-change: -4.48% -3.08%
Cycles are helped.
total spills in shared programs: 52 -> 52 (0.00%)
spills in affected programs: 0 -> 0
helped: 0
HURT: 0
total fills in shared programs: 94 -> 94 (0.00%)
fills in affected programs: 0 -> 0
helped: 0
HURT: 0
total sends in shared programs: 4240 -> 4240 (0.00%)
sends in affected programs: 0 -> 0
helped: 0
HURT: 0
LOST: 0
GAINED: 0
Rework: (Sagar)
- Adjust offset/indirect offset calculation.
- Add shader-db results
- Always calculate dword index
- Drop changes for indirect writes
Signed-off-by: Rohan Garg <rohan.garg@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27602>
The base class was used when we had vec4, but now we can fold it with
its only subclass. Declare fs_visitor now as a struct to be able to
forward declare for C code without causing errors due to class/struct
being mixed.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27861>
