There are unfortunately two distinct liveness analysis passes in the
compiler right now -- one good (but complex) pass used by RA based on
solving data flow equations, and one awful (but simple) pass used for
dead code elimination and bundling based on an abstract walk of the AST.
Let's move RA's pass into shared code so we can work on unifying.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
This allows us to fill in ctx->temp_count explicitly, even if we haven't
squished down the MIR.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
We already enforce this with the SSA/register distinction in the
backend. There is no need to duplicate this logic merely for an assert.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Now that we have constant adjustment logic abstracted, we can do this
safely. Along with the csel inversion patch, this allows many more
common csel ops to inline their condition in the bundle.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
If we can reuse constant slots from other instructions, we would like to
do so to include more instructions per bundle.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
If an instruction could be scheduled to vmul to satisfy the writeout
conditions, let's do that and save an instruction+cycle per fragment
shader.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
We still emit in-order but we switch to using the bundles created from
the new scheduler, which will allow greater flexibility and room for
out-of-order optimization.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
We require chosen instructions to be "close", to avoid ballooning
register pressure. This is a kludge that will go away once we have
proper liveness tracking in the scheduler, but for now it prevents a lot
of needless spilling.
v2: Lower threshold to 6 (from 8). Schedule is hurt, but a few shaders
that spilled excessively are fixed.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Derp
We can bundle two load/store together. This eliminates the need for
explicit load/store pairing in a prepass, as well.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Conditions for branches don't have a swizzle explicitly in the emitted
binary, but they do implicitly get swizzled in whatever instruction
wrote r31, so we need to handle that.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Conditional instructions (csel and conditional branches) require their
condition to be written to a special condition pipeline register (r31.w
for scalar, r31.xyzw for vector). However, pipeline registers are live
only for the duration of a single bundle. As such, the logic to schedule
conditionals correct is surprisingly complex. Essentially, we see if we
could stuff the conditional within the same bundle as the csel/branch
without breaking anything; if we can, we do that. If we can't, we add a
dummy move to make room.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
A bit of a kludge but allows setting an implicit dependency of synthetic
conditional moves on the actual condition, fixing code generated like:
vmul.feq r0, ..
sadd.imov r31, .., r0
vadd.fcsel [...]
The imov runs simultaneous with feq so it gets garbage results, but it's
too late to add an actual dependency practically speaking, since the new
synthetic imov doesn't have a node associated.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
In the future, we will want to keep track of which components of
constants of various sizes correspond to which parts of the bundle
constants, like in the old scheduler. For now, let's just stub it out
for a simple rule of one instruction with embedded constants per bundle.
We can eventually do better, of course.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
We don't actually do any scheduling here yet, but add per-tag helpers to
consume an instruction, print it, pop it off the worklist.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
It's not always obvious what the optimal bundle type should be. Let's
break out the logic to decide.
Currently set for purely in-order operation.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
After we've chosen an instruction, popped it off, and processed it, it's
time to update the worklist, removing that instruction from the
dependency graph to allow its dependents to be put onto the worklist.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
In the future, this routine will implement the core scheduling logic to
decide which instruction out of the worklist will be scheduled next, in
a way that minimizes cycle count and register pressure.
In the present, we are more interested in replicating in-order
scheduling with the much-more-powerful out-of-order model. So rather
than discriminating by a register pressure estimate, we simply choose
the latest possible instruction in the worklist.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
We would like to flatten a linked list of midgard_instructions into an
array of midgard_instruction pointers on the heap.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
It's not based on the writemask and it can't be inferred; it's just
intrinsic to the op itself.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
There's a missing prev_ldst = NULL; assignment in the new logic,
but even with this fixed it seems to regress some applications,
so let's revert the change until we find the real problem.
This reverts commit c9bebae287.
mir_foreach_instr_in_block_safe() is based on list_for_each_entry_safe()
which is designed to protect against removal of the current entry, but
removing the entry placed just after the current one will lead to a
use-after-free situation.
Luckily, the midgard_pair_load_store() logic guarantees that the
instruction being removed (if any) is never placed just after ins which
in turn guarantees that the hidden __next variable always points to a
valid object.
Took me a bit of time to realize that this code was safe, so I'm
suggesting to get rid of the inner mir_foreach_instr_in_block_from()
loop and rework the code so that the removed instruction is always the
current one (which is what the list_for_each_entry_safe() API was
initially designed for).
While at it, we also get rid of the unecessary insert(ins)/remove(ins)
dance by simply moving the instruction around.
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
list_for_each_entry() does not allow modifying the current item pointer.
Let's rework the skip-instructions logic in schedule_block() to not
break this rule.
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Set of opcodes doesn't have enough flexibility in certain cases. E.g.
Utgard PP has vector conditional select operation, but condition is always
scalar. Lowering all the vector selects to scalar increases instruction
number, so we need a way to filter only those ops that can't be handled
in hardware.
Reviewed-by: Qiang Yu <yuq825@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
These helpers are unused, as flagged by cppcheck.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
In practice, the new post-schedule print is just as useful.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
It has not been used in a long time; I forgot this file even existed.
Flagged by cppcheck.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
We already had a perfectly cromulent pass for this, but one landed in
common NIR code so let's switch and lighten our tree.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
This optimization depended on RA running before scheduling. It therefore
no longer applies and is now unused.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
This is a tradeoff.
Scheduling before RA means we don't do RA on what-will-become pipeline
registers. Importantly, it means the scheduler is able to reorder
instructions, as registers have not been decided yet.
Unfortunately, it also complicates register spilling, since the spills
themselves won't get bundled optimally and we can only spill twice per
ALU bundle (only one spill per bundle allowed here). It also prevents us
from eliminating dead moves introduced by register allocation, as they
are not dead before RA. The shader-db regressions are from poor spilling
choices introduced by the new bundling requirements. These could be
solved by the combination of a post-scheduler (to combine adjacent
spills into bundles) with a VLIW-aware spill cost calculation.
Nevertheless, the change is small enough that I feel it's worth it to
eat a tiny shader-db regression for the sake of flexibility.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Rather than using a pile of hacks and awkward constructs in MIR to
ensure the writeout parameter gets written into r0, let's add a
dedicated shadow register class for writeout (interfering with work
register r0) so we can express the writeout condition succintly and
directly.
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
