The LDS output queue is accessed via the OQAP register. The OQAP
register cannot be live across clauses, so if value is written to the
output queue, it must be retrieved before the end of the clause.
With the machine scheduler, we cannot statisfy this constraint, because
it lacks proper alias analysis and it will mark some LDS accesses as
having a chain dependency on vertex fetches. Since vertex fetches
require a new clauses, the dependency may end up spiltting OQAP uses and
defs so the end up in different clauses. See the lds-output-queue.ll
test for a more detailed explanation.
To work around this issue, we now combine the LDS read and the OQAP
copy into one instruction and expand it after register allocation.
This patch also adds some checks to the EmitClauseMarker pass, so that
it doesn't end a clause with a value still in the output queue and
removes AR.X and OQAP handling from the scheduler (AR.X uses and defs
were already being expanded post-RA, so the scheduler will never see
them).
Reviewed-by: Vincent Lejeune <vljn at ovi.com>
llvm-svn: 194755
This is using a hint from AMD APP OpenCL Programming Guide with
empirically tweaked parameters.
I used Unigine Heaven 3.0 to determine best parameters on my system
(i7 2600/Radeon 6950/Kernel 3.9.4) the benchmark :
it went from 38.8 average fps to 39.6, which is ~3% gain.
(Lightmark 2008.2 gain is much more marginal: from 537 to 539)
There is no lit test provided as the parameter were determined
empirically and it it would be nearly impossiblet to find a test
program that check for optimal behavior.
llvm-svn: 183593
This is a skeleton for a pre-RA MachineInstr scheduler strategy. Currently
it only tries to expose more parallelism for ALU instructions (this also
makes the distribution of GPR channels more uniform and increases the
chances of ALU instructions to be packed together in a single VLIW group).
Also it tries to reduce clause switching by grouping instruction of the
same kind (ALU/FETCH/CF) together.
Vincent Lejeune:
- Support for VLIW4 Slot assignement
- Recomputation of ScheduleDAG to get more parallelism opportunities
Tom Stellard:
- Fix assertion failure when trying to determine an instruction's slot
based on its destination register's class
- Fix some compiler warnings
Vincent Lejeune: [v2]
- Remove recomputation of ScheduleDAG (will be provided in a later patch)
- Improve estimation of an ALU clause size so that heuristic does not emit cf
instructions at the wrong position.
- Make schedule heuristic smarter using SUnit Depth
- Take constant read limitations into account
Vincent Lejeune: [v3]
- Fix some uninitialized values in ConstPair
- Add asserts to ensure an ALU slot is always populated
llvm-svn: 176498
Craig Topper