Using LIS can be quite expensive, so caching of calculated region
live-ins and pressure is implemented. It does two things:
1. Caches the info for the second stage when we schedule with
decreased target occupancy.
2. Tracks the basic block from top to bottom thus eliminating the
need to scan whole register file liveness at every region split
in the middle of the block.
The scheduling is now done in 3 stages instead of two, with the first
one being really a no-op and only used to collect scheduling regions
as sent by the scheduler driver.
There is no functional change to the current behavior, only compilation
speed is affected. In general computeBlockPressure() could be simplified
if we switch to backward RP tracker, because scheduler sends regions
within a block starting from the last upward. We could use a natural
order of upward tracker to seamlessly change between regions of the same
block, since live reg set of a previous tracked region would become a
live-out of the next region. That however requires fixing upward tracker
to properly account defs and uses of the same instruction as both are
contributing to the current pressure. When we converge on the produced
pressure we should be able to switch between them back and forth. In
addition, backward tracker is less expensive as it uses LIS in recede
less often than forward uses it in advance.
At the moment the worst known case compilation time has improved from 26
minutes to 8.5.
Differential Revision: https://reviews.llvm.org/D33117
llvm-svn: 303184
This factors register pressure estimation mechanism from the
GCNSchedStrategy into the forward tracker to unify interface
with other strategies and expose it to other interested phases.
Differential Revision: https://reviews.llvm.org/D33105
llvm-svn: 303179
Earlier fix D32572 introduced a bug where live-ins were calculated
for basic block instead of scheduling region. This change fixes it.
Differential Revision: https://reviews.llvm.org/D33086
llvm-svn: 302812
This is incorrect to record region boundaries before scheduling,
it may change after scheduling. As a result second pass may see less
instructions to schedule than it should.
Differential Revision: https://reviews.llvm.org/D31434
llvm-svn: 298945
This method inverts the Reason field of a scheduling candidate.
It does right comparison between RegCritical and RegExcess, but
everything else is broken. In fact it can prefer less strong reason
such as Weak over RegCritical because Weak > -RegCritical.
The CandReason enum is properly sorted, so just remove artificial
ranking.
Differential Revision: https://reviews.llvm.org/D30557
llvm-svn: 297536
If during scheduling we have identified that we cannot keep optimistic
occupancy increase critical register pressure limit and try scheduling
of the whole function again. In this case blocks with smaller pressure
will have a chance for better scheduling.
Differential Revision: https://reviews.llvm.org/D30442
llvm-svn: 296506
This change introduces new method to estimate register pressure in
GCNScheduler. Standard RPTracker gives huge error due to the following
reasons:
1. It does not account for live-ins or live-outs if value is not used
in the region itself. That creates a huge error in a very common case
if there are a lot of live-thu registers.
2. It does not properly count subregs.
3. It assumes a register used as an input operand can be reused as an
output. This is not always possible by itself, this is not what RA
will finally do in many cases for various reasons not limited to RA's
inability to do so, and this is not so if the value is actually a
live-thu.
In addition we can now see clear separation between live-in pressure
which we cannot change with the scheduling and tentative pressure
which we can change.
Differential Revision: https://reviews.llvm.org/D30439
llvm-svn: 296491
If two subregs of the same register are defined and we need to revert
schedule changing def order, we will end up with both instructions
having def,read-undef flags because adjustLaneLiveness() will only set
this flag but will not remove it.
Fix this by removing read-undef flags before calling adjustLaneLiveness.
Differential Revision: https://reviews.llvm.org/D30428
llvm-svn: 296484
This patch reverts region's scheduling to the original untouched state
in case if we have have decreased occupancy.
In addition it switches to use TargetRegisterInfo occupancy callback
for pressure limits instead of gradually increasing limits which were
just passed by. We are going to stay with the best schedule so we do
not need to tolerate worsened scheduling anymore.
Differential Revision: https://reviews.llvm.org/D29971
llvm-svn: 295206
Functions matching LDS use to occupancy return results for a workgroup
of 64 workitems. The numbers has to be adjusted for bigger workgroups.
For example a workgroup of size 256 already occupies 4 waves just by
itself. Given that all numbers of LDS use in the compiler are per
workgroup, occupancy shall be multiplied by 4 in this case. Each 64
workitems still limited by the same number, but 4 subrgoups 64 workitems
each can afford 4 times more LDS to get the same occupancy.
In addition change initializes LDS size in the subtarget to a real value
for SI+ targets. This is required since LDS size is a variable in these
calculations.
Differential Revision: https://reviews.llvm.org/D29423
llvm-svn: 293837
Summary:
There is no point in setting SGPRS=104, because VI allocates SGPRs
in multiples of 16, so 104 -> 112. That enables us to use all 102 SGPRs
for general purposes.
Reviewers: tstellarAMD
Subscribers: qcolombet, arsenm, kzhuravl, wdng, nhaehnle, yaxunl, tony-tye
Differential Revision: https://reviews.llvm.org/D27149
llvm-svn: 289260
- Implemented amdgpu-flat-work-group-size attribute
- Implemented amdgpu-num-active-waves-per-eu attribute
- Implemented amdgpu-num-sgpr attribute
- Implemented amdgpu-num-vgpr attribute
- Dynamic LDS constraints are in a separate patch
Patch by Tom Stellard and Konstantin Zhuravlyov
Differential Revision: https://reviews.llvm.org/D21562
llvm-svn: 280747
Stanislav Mekhanoshin