Nothing produces them any more, so remove them from NIR. This massively reduces
the size of nir_src, which should improve performance all over.
nir_src size reduced from 56 bytes -> 40 bytes (pahole results on arm64, x86_64
should be similar.)
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24253>
At this point, everything is SSA. Also, NIR no longer allows different
numbers of components on the two sides of a phi so we can just assert
rather than trying to gracefully handle mismatches.
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23089>
A number of passes lower SSA partially to registers, do work that would be
invalid in SSA, and then go back into SSA with nir_lower_regs_to_ssa. As a step
towards replacing nir_register with intrinsics,
the nir_lower_{phis,ssa_defs}_to_regs passes are changed to produce intrinsics
instead of nir_registers, and their callers are updated to call
nir_lower_reg_intrinsics_to_ssa instead of nir_lower_regs_to_ssa to compensate.
Jointly authored with Faith.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23089>
It doesn't do anything yet. We leave that to the subsequent patches so we can
keep the tree-wide refactor as simple as possible.
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23089>
This frees up the shorter names for the new register-based intrinsics.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Acked-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23956>
Done by hand at each call site but going very quickly with funny Vim motions and
common regexes. This is a very common idiom in NIR.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23807>
Since 624e799cc3 ("nir: Drop nir_ssa_def::name and nir_register::name"), SSA
defs don't have names, making the name argument unused. Drop it from the
signature and fix the call sites. This was done with the help of the following
Coccinelle semantic patch:
@@
expression A, B, C, D, E;
@@
-nir_ssa_dest_init(A, B, C, D, E);
+nir_ssa_dest_init(A, B, C, D);
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23078>
We have a helper, don't open code it.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22967>
The pattern shows up all the time open-coded. Use the macro instead.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22967>
Every nir_ssa_def is part of a chain of uses, implemented with doubly linked
lists. That means each requires 2 * 64-bit = 16 bytes per def, which is
memory intensive. Together they require 32 bytes per def. Not cool.
To cut that memory use in half, we can combine the two linked lists into a
single use list that contains both regular instruction uses and if-uses. To do
this, we augment the nir_src with a boolean "is_if", and reimplement the
abstract if-uses operations on top of that list. That boolean should fit into
the padding already in nir_src so should not actually affect memory use, and in
the future we sneak it into the bottom bit of a pointer.
However, this creates a new inefficiency: now iterating over regular uses
separate from if-uses is (nominally) more expensive. It turns out virtually
every caller of nir_foreach_if_use(_safe) also calls nir_foreach_use(_safe)
immediately before, so we rewrite most of the callers to instead call a new
single `nir_foreach_use_including_if(_safe)` which predicates the logic based on
`src->is_if`. This should mitigate the performance difference.
There's a bit of churn, but this is largely a mechanical set of changes.
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22343>
We loop, effectively, over two stacks: ready and to_do and finish only
when both are empty. In the case where ready is empty, we pull one off
of to_do, add a copy to a temporary, and push it onto the ready stack.
Previously, we assumed that we would never get to the temporary copy
case if to_do has exactly one entry because that would imply that there
was only one copy left which means there can't possibly be a cycle to
break. This was true until c7fc44f9eb ("nir/from_ssa: Respect and
populate divergence information") which changed things such that
temporary copies sometimes get added in the case where a convergent
value is copied both to convergent and divergent destinations.
This patch adjusts our loop iteration to always attempt to clear the
ready stack before checking if there's anything left on the to_do stack.
I also added an assert to make the exit condition more clear.
Fixes: c7fc44f9eb ("nir/from_ssa: Respect and populate divergence information")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/8037
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21315>
There is an optimization in the parallel copy algorithm where, after a
copy has been performed, we can treat the destination as the new source
for future copies of the same source. In particular, consider the
following parallel copy: A -> B, C -> A, A -> C. In this case, after we
have done the A -> B copy, we can make note that the value in A is now
in B and emit the sequence: A -> B, C -> A, B -> C. This allows us to
resolve the swap cycle between A anc C without allocating a temporary
register because we know B is also a copy of A.
When one of the registers involved is convergent and the other is
divergent, this optimization is problematic because, while convergent to
divergent copies are fine, we can't re-use the divergent copy in later
copies if any of those copies are to a convergent variable. We could,
but it would require a read_first_invocation which would get messy. In
In c7fc44f9eb ("nir/from_ssa: Respect and populate divergence
information"), we attempted to deal with this by limiting the rename
optimization to the case where the divergence matched.
The problem is that we did the re-name part whenever the divergence
matched but only marked it as ready if the thing being copied was a
destination. (We actually left two instances of loc[a] = b, one which
always happened and one which only happened if we also wanted to flag
the source as being ready to use as a destination.) While this
technically doesn't cause any problems, it may result in more inter-mov
dependencies which hurts instruction scheduling. For example, if we had
the parallel copy A -> B, A -> C, A -> D, we now end up emitting the
sequence A -> B, B -> C, C -> D which has many more data hazards between
instructions caused by the constant shuffling.
This commit restores the original logic in which we only perform the
rename optimization if the rename would free up a register we will later
use as a destination. This isn't entirely optimal as it still doesn't
prove that there is a cycle involved first, but it should lead to a
reduction in unnecessary dependencies.
No shader-db changes on SKL or DG2
Fixes: c7fc44f9eb ("nir/from_ssa: Respect and populate divergence information")
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21315>
This is almost always a nir_instr and updating the src of a nir_if will
have to work slightly differently in the future.
Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Acked-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12910>
Is a phi source is an undef, there's no point in copying it or really
caring about it at all. We would just end up inserting a mov from an
undef to a register. Instead, treat phi sources which point to an undef
as if the phi source doesn't exist.
This also prevents them from being included in phi webs which should
reduce the overall interference seen in the shader. Currently, if two
phis share an undef, their phi webs are consdiered to interfere. By
ignoring undefs we can get rid of this false interference and reduce the
size of phi webs. Reducing the number of things being copied by the
parallel copy instructions should also free up the paralle copy
algorithm and reduce the over-all churn of movs.
Shader-db results on Haswell:
total instructions in shared programs: 8156608 -> 8155406 (-0.01%)
instructions in affected programs: 164838 -> 163636 (-0.73%)
Shader-db results on Skylake:
total instructions in shared programs: 18227370 -> 18227359 (<.01%)
instructions in affected programs: 519 -> 508 (-2.12%)
helped: 6
HURT: 0
Shader-db results on Tigerlake:
total instructions in shared programs: 21167987 -> 21168025 (<.01%)
instructions in affected programs: 23701 -> 23739 (0.16%)
helped: 21
HURT: 27
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16817>
During certain control-flow manipulation passes, we go out-of-SSA
temporarily in certain areas of the code to make control-flow
manipulation easier. This can result in registers being in phi sources
temporarily. If two sub-passes run before we get a chance to do
clean-up, we can end up doing some out-of-SSA and then a bit more
out-of-SSA and trigger this case. It's easy enough to handle.
Fixes: a620f66872 ("nir: Add a couple quick-and-dirty out-of-SSA helpers")
Fixes: 79a987ad2a ("nir/opt_if: also merge break statements with ones after the branch")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6370
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16111>
In some non-trivial cases (the amber script file in the merge
request description) phi instruction has more than 32 elements
in predecessors tree and that isn't recursion, just large tree.
In that case, phis not fully converted into a register or mov,
but successfully removed.
The fix removes the counter and adds container of visited blocks.
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/3690
Cc: mesa-stable
Signed-off-by: Mykhailo Skorokhodov <mykhailo.skorokhodov@globallogic.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13710>
We were using the ralloc parent in some places, which should work out to
be the shader I think, but to de-ralloc the instrs we should just pass the
existing shader pointer in.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11776>
This code was being tricky with passing a mem_ctx instead of the shader,
then freeing the mem_ctx when the pass was done and all the parallel
copies had been removed from the shader. Use the right type for instr
creation and do a bit of manual list management to prepare the way for
non-ralloc NIR instrs.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11776>
We say that they're for debug only but we don't really have a good
policy around when to set them and when not to. In particular,
nir_lower_system_values and nir_lower_vars_to_ssa which are the chief
producers of SSA values which might reasonably have a name do not bother
to set one. We have some names set from things like BLORP and RADV's
meta shaders but AFAICT, they're setting a name more because it's there
than because they actually care.
Also, most things other than nir_clone and nir_serialize don't bother to
try and preserve them. You can see in the diffstat of this commit
exactly what passes attempt to preserve names. Notably missing from the
list is opt_algebraic which is the single largest source of SSA def
churn and it happily throws names away.
These observations lead me to question whether or not names are actually
useful at all or if they're just taking up space (8B per instruction)
and wasting CPU cycles (to ralloc_strdup on the off chance we do have
one). I don't think I can think of a single time in recent history
where I've been debugging a shader issue and a SSA value name has been
there and been useful. If anything, the few times they are there, they
just throw me off because they mess up the indentation in nir_print.
iris shader-db on my system gets runtime -2.07734% +/- 1.26933% (n=5)
Reviewed-by: Emma Anholt <emma@anholt.net>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5439>
This was renamed when I was in high school. I remember updating the
Midgard compiler while sitting in AP Physics.
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10296>
This commit replaces the new_src parameter of nir_ssa_def_rewrite_uses()
with an SSA def, removes nir_ssa_def_rewrite_uses_ssa(), and rewrites
all the users as needed.
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Acked-by: Alyssa Rosenzweig <alyssa@collabora.com>
Acked-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9383>
This is currently an alias for nir_ssa_def_rewrite_uses but we move all
the instances which used it to write a non-SSA source to the newly named
helper.
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Acked-by: Alyssa Rosenzweig <alyssa@collabora.com>
Acked-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9383>
