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llvm-svn: 351636
When doing some instruction scheduling work, we noticed some missing itineraries.
Before we switch to machine scheduler, those missing itineraries might not have impact to actually scheduling,
because we can still get same latency due to default values.
With machine scheduler, however, itineraries will have impact to scheduling.
eg: NumMicroOps will default to be 0 if there is NO itineraries for specific instruction class.
And most of the instruction class with itineraries will have NumMicroOps default to 1.
This will has impact on the count of RetiredMOps, affects the Pending/Available Queue,
then causing different scheduling or suboptimal scheduling further.
This patch is for STWU/STWUX (IIC_LdStStoreUpd ) for P8.
Since there are already multiple IIC for store update, this patch also merge
IIC_LdStSTDU/IIC_LdStStoreUpd to IIC_LdStSTU
IIC_LdStSTDUX to IIC_LdStSTUX
and we add a new testcase in https://reviews.llvm.org/D54699 to show the difference.
Differential Revision: https://reviews.llvm.org/D54700
llvm-svn: 347311
When doing some instruction scheduling work, we noticed some missing itineraries.
Before we switch to machine scheduler, those missing itineraries might not have impact to actually scheduling,
because we can still get same latency due to default values.
With machine scheduler, however, itineraries will have impact to scheduling.
eg: NumMicroOps will default to be 0 if there is NO itineraries for specific instruction class.
And most of the instruction class with itineraries will have NumMicroOps default to 1.
This will has impact on the count of RetiredMOps, affects the Pending/Available Queue,
then causing different scheduling or suboptimal scheduling further.
Patch By: jsji (Jinsong Ji)
Differential Revision: https://reviews.llvm.org/D52040
llvm-svn: 342441
When doing some instruction scheduling work, we noticed some missing itineraries.
Before we switch to machine scheduler, those missing itineraries might not have impact to actually scheduling,
because we can still get same latency due to default values.
With machine scheduler, however, itineraries will have impact to scheduling.
eg: NumMicroOps will default to be 0 if there is NO itineraries for specific instruction class.
And most of the instruction class with itineraries will have NumMicroOps default to 1.
This will has impact on the count of RetiredMOps, affects the Pending/Available Queue,
then causing different scheduling or suboptimal scheduling further.
Patch by jsji (Jinsong Ji)
Differential Revision: https://reviews.llvm.org/D51506
llvm-svn: 341293
Summary:
We don't use MinLatency any more since r184032.
Reviewers: atrick, hfinkel, mcrosier
Differential Revision: http://reviews.llvm.org/D19474
llvm-svn: 267502
TableGen checks at compiletime that for scheduling models with
"CompleteModel = 1" one of the following holds:
- Is marked with the hasNoSchedulingInfo flag
- The instruction is a subclass of Sched
- There are InstRW definitions in the scheduling model
Typical steps necessary to complete a model:
- Ensure all pseudo instructions that are expanded before machine
scheduling (usually everything handled with EmitYYY() functions in
XXXTargetLowering).
- If a CPU does not support some instructions mark the corresponding
resource unsupported: "WriteRes<WriteXXX, []> { let Unsupported = 1; }".
- Add missing scheduling information.
Differential Revision: http://reviews.llvm.org/D17747
llvm-svn: 262384
PowerPC uses itineraries to describe processor pipelines (and dispatch-group
restrictions for P7/P8 cores). Unfortunately, the target-independent
implementation of TII.getInstrLatency calls ItinData->getStageLatency, and that
looks for the largest cycle count in the pipeline for any given instruction.
This, however, yields the wrong answer for the PPC itineraries, because we
don't encode the full pipeline. Because the functional units are fully
pipelined, we only model the initial stages (there are no relevant hazards in
the later stages to model), and so the technique employed by getStageLatency
does not really work. Instead, we should take the maximum output operand
latency, and that's what PPCInstrInfo::getInstrLatency now does.
This caused some test-case churn, including two unfortunate side effects.
First, the new arrangement of copies we get from function parameters now
sometimes blocks VSX FMA mutation (a FIXME has been added to the code and the
test cases), and we have one significant test-suite regression:
SingleSource/Benchmarks/BenchmarkGame/spectral-norm
56.4185% +/- 18.9398%
In this benchmark we have a loop with a vectorized FP divide, and it with the
new scheduling both divides end up in the same dispatch group (which in this
case seems to cause a problem, although why is not exactly clear). The grouping
structure is hard to predict from the bottom of the loop, and there may not be
much we can do to fix this.
Very few other test-suite performance effects were really significant, but
almost all weakly favor this change. However, in light of the issues
highlighted above, I've left the old behavior available via a
command-line flag.
llvm-svn: 242188
isel is actually a cracked instruction on the P7/P8, and must start a dispatch
group. The scheduling model should reflect this so that we don't bunch too many
of them together when possible.
Thanks to Bill Schmidt and Pat Haugen for helping to sort this out.
llvm-svn: 227758
Now that the way that the partial unrolling threshold for small loops is used
to compute the unrolling factor as been corrected, a slightly smaller threshold
is preferable. This is expected; other targets may need to re-tune as well.
llvm-svn: 225566
The P7 benefits from not have really-small loops so that we either have
multiple dispatch groups in the loop and/or the ability to form more-full
dispatch groups during scheduling. Setting the partial unrolling threshold to
44 seems good, empirically, for the P7. Compared to using no late partial
unrolling, this yields the following test-suite speedups:
SingleSource/Benchmarks/Adobe-C++/simple_types_constant_folding
-66.3253% +/- 24.1975%
SingleSource/Benchmarks/Misc-C++/oopack_v1p8
-44.0169% +/- 29.4881%
SingleSource/Benchmarks/Misc/pi
-27.8351% +/- 12.2712%
SingleSource/Benchmarks/Stanford/Bubblesort
-30.9898% +/- 22.4647%
I've speculatively added a similar setting for the P8. Also, I've noticed that
the unroller does not quite calculate the unrolling factor correctly for really
tiny loops because it neglects to account for the fact that not every loop body
replicant contains an ending branch and counter increment. I'll fix that later.
llvm-svn: 225522
Chandler Carruth