Summary:
Subtargets can define the libpfm counter names that can be used to
measure cycles and uops issued on ProcResUnits.
This allows making llvm-exegesis available on more targets.
Fixes PR36984.
Reviewers: gchatelet, RKSimon, andreadb, craig.topper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D45360
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@329675 91177308-0d34-0410-b5e6-96231b3b80d8
This patch adds the ability to describe properties of the hardware retire
control unit.
Tablegen class RetireControlUnit has been added for this purpose (see
TargetSchedule.td).
A RetireControlUnit specifies the size of the reorder buffer, as well as the
maximum number of opcodes that can be retired every cycle.
A zero (or negative) value for the reorder buffer size means: "the size is
unknown". If the size is unknown, then llvm-mca defaults it to the value of
field SchedMachineModel::MicroOpBufferSize. A zero or negative number of
opcodes retired per cycle means: "there is no restriction on the number of
instructions that can be retired every cycle".
Models can optionally specify an instance of RetireControlUnit. There can only
be up-to one RetireControlUnit definition per scheduling model.
Information related to the RCU (RetireControlUnit) is stored in (two new fields
of) MCExtraProcessorInfo. llvm-mca loads that information when it initializes
the DispatchUnit / RetireControlUnit (see Dispatch.h/Dispatch.cpp).
This patch fixes PR36661.
Differential Revision: https://reviews.llvm.org/D45259
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This patch allows the description of register files in processor scheduling
models. This addresses PR36662.
A new tablegen class named 'RegisterFile' has been added to TargetSchedule.td.
Targets can optionally describe register files for their processors using that
class. In particular, class RegisterFile allows to specify:
- The total number of physical registers.
- Which target registers are accessible through the register file.
- The cost of allocating a register at register renaming stage.
Example (from this patch - see file X86/X86ScheduleBtVer2.td)
def FpuPRF : RegisterFile<72, [VR64, VR128, VR256], [1, 1, 2]>
Here, FpuPRF describes a register file for MMX/XMM/YMM registers. On Jaguar
(btver2), a YMM register definition consumes 2 physical registers, while MMX/XMM
register definitions only cost 1 physical register.
The syntax allows to specify an empty set of register classes. An empty set of
register classes means: this register file models all the registers specified by
the Target. For each register class, users can specify an optional register
cost. By default, register costs default to 1. A value of 0 for the number of
physical registers means: "this register file has an unbounded number of
physical registers".
This patch is structured in two parts.
* Part 1 - MC/Tablegen *
A first part adds the tablegen definition of RegisterFile, and teaches the
SubtargetEmitter how to emit information related to register files.
Information about register files is accessible through an instance of
MCExtraProcessorInfo.
The idea behind this design is to logically partition the processor description
which is only used by external tools (like llvm-mca) from the processor
information used by the llvm machine schedulers.
I think that this design would make easier for targets to get rid of the extra
processor information if they don't want it.
* Part 2 - llvm-mca related *
The second part of this patch is related to changes to llvm-mca.
The main differences are:
1) class RegisterFile now needs to take into account the "cost of a register"
when allocating physical registers at register renaming stage.
2) Point 1. triggered a minor refactoring which lef to the removal of the
"maximum 32 register files" restriction.
3) The BackendStatistics view has been updated so that we can print out extra
details related to each register file implemented by the processor.
The effect of point 3. is also visible in tests register-files-[1..5].s.
Differential Revision: https://reviews.llvm.org/D44980
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Currently isComplete = 1 requires that every instruction must
be described, declared unsupported or marked as having no
scheduling information for a processor.
For some backends such as MIPS, this requirement entails
long regex lists of instructions that are unsupported.
This patch teaches Tablegen to skip over instructions that
are associated with unsupported feature when checking if the
scheduling model is complete.
Patch by: Daniel Sanders
Contributions by: Simon Dardis
Reviewers: MatzeB
Differential Reviewer: http://reviews.llvm.org/D20522
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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
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Add header guards to files that were missing guards. Remove #endif comments
as they don't seem common in LLVM (we can easily add them back if we decide
they're useful)
Changes made by clang-tidy with minor tweaks.
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Sweep the codebase for common typos. Includes some changes to visible function
names that were misspelt.
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We always supported a mixture of the old itinerary model and new
per-operand model, but it required a level of indirection to map
itinerary classes to SchedRW lists. This was done for ARM A9.
Now we want to define x86 SchedRW lists, with the goal of removing its
itinerary classes, but still support the itineraries in the mean
time. When I original developed the model, Atom did not have
itineraries, so there was no reason to expect this requirement.
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I've tried to find main moudle headers where possible, but the TableGen
stuff may warrant someone else looking at it.
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This allows the processor-specific machine model to override selected
base opcodes without any fanciness.
e.g. InstRW<[CoreXWriteVANDP], (instregex "VANDP")>.
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A processor can now arbitrarily alias one SchedWrite onto
another. Only the SchedAlias definition need be within the processor
model. The aliased SchedWrite may be a SchedVariant, WriteSequence, or
transitively refer to another alias.
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subtarget CPU descriptions and support new features of
MachineScheduler.
MachineModel has three categories of data:
1) Basic properties for coarse grained instruction cost model.
2) Scheduler Read/Write resources for simple per-opcode and operand cost model (TBD).
3) Instruction itineraties for detailed per-cycle reservation tables.
These will all live side-by-side. Any subtarget can use any
combination of them. Instruction itineraries will not change in the
near term. In the long run, I expect them to only be relevant for
in-order VLIW machines that have complex contraints and require a
precise scheduling/bundling model. Once itineraries are only actively
used by VLIW-ish targets, they could be replaced by something more
appropriate for those targets.
This tablegen backend rewrite sets things up for introducing
MachineModel type #2: per opcode/operand cost model.
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