Don't declare them as X86SchedWritePair when the folded class will never be used.
Note: MOVBE (load/store endian conversion) instructions tend to have a very different behaviour to BSWAP.
llvm-svn: 338412
This patch fixes the latency/throughput of LEA instructions in the BtVer2
scheduling model.
On Jaguar, A 3-operands LEA has a latency of 2cy, and a reciprocal throughput of
1. That is because it uses one cycle of SAGU followed by 1cy of ALU1. An LEA
with a "Scale" operand is also slow, and it has the same latency profile as the
3-operands LEA. An LEA16r has a latency of 3cy, and a throughput of 0.5 (i.e.
RThrouhgput of 2.0).
This patch adds a new TIIPredicate named IsThreeOperandsLEAFn to X86Schedule.td.
The tablegen backend (for instruction-info) expands that definition into this
(file X86GenInstrInfo.inc):
```
static bool isThreeOperandsLEA(const MachineInstr &MI) {
return (
(
MI.getOpcode() == X86::LEA32r
|| MI.getOpcode() == X86::LEA64r
|| MI.getOpcode() == X86::LEA64_32r
|| MI.getOpcode() == X86::LEA16r
)
&& MI.getOperand(1).isReg()
&& MI.getOperand(1).getReg() != 0
&& MI.getOperand(3).isReg()
&& MI.getOperand(3).getReg() != 0
&& (
(
MI.getOperand(4).isImm()
&& MI.getOperand(4).getImm() != 0
)
|| (MI.getOperand(4).isGlobal())
)
);
}
```
A similar method is generated in the X86_MC namespace, and included into
X86MCTargetDesc.cpp (the declaration lives in X86MCTargetDesc.h).
Back to the BtVer2 scheduling model:
A new scheduling predicate named JSlowLEAPredicate now checks if either the
instruction is a three-operands LEA, or it is an LEA with a Scale value
different than 1.
A variant scheduling class uses that new predicate to correctly select the
appropriate latency profile.
Differential Revision: https://reviews.llvm.org/D49436
llvm-svn: 337469
registers.
The goal of this patch is to improve the throughput analysis in llvm-mca for the
case where instructions perform partial register writes.
On x86, partial register writes are quite difficult to model, mainly because
different processors tend to implement different register merging schemes in
hardware.
When the code contains partial register writes, the IPC (instructions per
cycles) estimated by llvm-mca tends to diverge quite significantly from the
observed IPC (using perf).
Modern AMD processors (at least, from Bulldozer onwards) don't rename partial
registers. Quoting Agner Fog's microarchitecture.pdf:
" The processor always keeps the different parts of an integer register together.
For example, AL and AH are not treated as independent by the out-of-order
execution mechanism. An instruction that writes to part of a register will
therefore have a false dependence on any previous write to the same register or
any part of it."
This patch is a first important step towards improving the analysis of partial
register updates. It changes the semantic of RegisterFile descriptors in
tablegen, and teaches llvm-mca how to identify false dependences in the presence
of partial register writes (for more details: see the new code comments in
include/Target/TargetSchedule.h - class RegisterFile).
This patch doesn't address the case where a write to a part of a register is
followed by a read from the whole register. On Intel chips, high8 registers
(AH/BH/CH/DH)) can be stored in separate physical registers. However, a later
(dirty) read of the full register (example: AX/EAX) triggers a merge uOp, which
adds extra latency (and potentially affects the pipe usage).
This is a very interesting article on the subject with a very informative answer
from Peter Cordes:
https://stackoverflow.com/questions/45660139/how-exactly-do-partial-registers-on-haswell-skylake-perform-writing-al-seems-to
In future, the definition of RegisterFile can be extended with extra information
that may be used to identify delays caused by merge opcodes triggered by a dirty
read of a partial write.
Differential Revision: https://reviews.llvm.org/D49196
llvm-svn: 337123
Summary:
{F6603964}
While there is still some discrepancies within that new group,
it is clearly separate from the other shifts.
And Agner's tables agree, these double shifts are clearly
different from the normal shifts/rotates.
I'm guessing `FeatureSlowSHLD` is related.
Indeed, a basic sched pair is *not* the /best/ match.
But keeping it in the WriteShift is /clearly/ not ideal either.
This can and likely will be fine-tuned later.
This is purely mechanical change, it does not change any numbers,
as the [lack of the change of] mca tests show.
Reviewers: craig.topper, RKSimon, andreadb
Reviewed By: craig.topper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D49015
llvm-svn: 336515
Summary:
Motivation: {F6597954}
This only does the mechanical splitting, does not actually change
any numbers, as the tests added in previous revision show.
Reviewers: craig.topper, RKSimon, courbet
Reviewed By: craig.topper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D48998
llvm-svn: 336511
Summary:
I ran llvm-exegesis on SKX, SKL, BDW, HSW, SNB.
Atom is from Agner and SLM is a guess.
I've left AMD processors alone.
Reviewers: RKSimon, craig.topper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D48079
llvm-svn: 335097
Summary:
This fixes most of the scheduling info for SKX vector operations.
I had to split a lot of the YMM/ZMM classes into separate classes for YMM and ZMM.
The before/after llvm-exegesis analysis are in the phabricator diff.
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D47721
llvm-svn: 334407
Summary: In preparation for D47721. HSW and SNB still define unsupported
classes as they are used by KNL and generic models respectively.
Reviewers: RKSimon
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D47763
llvm-svn: 334389
As detailed on Agner's Microarchitecture doc (21.8 AMD Bobcat and Jaguar pipeline - Dependency-breaking instructions), these instructions are dependency breaking and fast-path zero the destination register (and appropriate EFLAGS bits).
llvm-svn: 334303
As detailed on Agner's Microarchitecture doc (21.8 AMD Bobcat and Jaguar pipeline - Dependency-breaking instructions), all these instructions are dependency breaking and zero the destination register.
llvm-svn: 334119
This patch is the last of a sequence of three patches related to LLVM-dev RFC
"MC support for variant scheduling classes".
http://lists.llvm.org/pipermail/llvm-dev/2018-May/123181.html
This fixes PR36672.
The main goal of this patch is to teach llvm-mca how to solve variant scheduling
classes. This patch does that, plus it adds new variant scheduling classes to
the BtVer2 scheduling model to identify so-called zero-idioms (i.e. so-called
dependency breaking instructions that are known to generate zero, and that are
optimized out in hardware at register renaming stage).
Without the BtVer2 change, this patch would not have had any meaningful tests.
This patch is effectively the union of two changes:
1) a change that teaches llvm-mca how to resolve variant scheduling classes.
2) a change to the BtVer2 scheduling model that allows us to special-case
packed XOR zero-idioms (this partially fixes PR36671).
Differential Revision: https://reviews.llvm.org/D47374
llvm-svn: 333909
Summary:
{FLDL2E, FLDL2T, FLDLG2, FLDLN2, FLDPI} were using WriteMicrocoded.
- I've measured the values for Broadwell, Haswell, SandyBridge, Skylake.
- For ZnVer1 and Atom, values were transferred form InstRWs.
- For SLM and BtVer2, I've guessed some values :(
Reviewers: RKSimon, craig.topper, andreadb
Subscribers: gbedwell, llvm-commits
Differential Revision: https://reviews.llvm.org/D47585
llvm-svn: 333656
Summary:
- I've measured the values for Broadwell, Haswell, SandyBridge, Skylake.
- For ZnVer1 and Atom, values were transferred form `InstRW`s.
- For SLM and BtVer2, values are from Agner.
This is split off from https://reviews.llvm.org/D47377
Reviewers: RKSimon, andreadb
Subscribers: gbedwell, llvm-commits
Differential Revision: https://reviews.llvm.org/D47523
llvm-svn: 333642
BtVer2 - fix NumMicroOp and account for the Lat+6cy GPR->XMM and Lat+1cy XMm->GPR delays (see rL332737)
The high number of MOVD/MOVQ equivalent instructions meant that there were a number of missed patterns in SNB/Znver1:
SNB - add missing GPR<->MMX costs (taken from Agner / Intel AOM)
Znver1 - add missing GPR<->XMM MOVQ costs (taken from Agner)
llvm-svn: 332745
A lot of the models still have too many InstRW overrides for these new classes - this needs cleaning up but I wanted to get the classes in first
llvm-svn: 332451
BtVer2 - Fixes schedules for (V)CVTPS2PD instructions
A lot of the Intel models still have too many InstRW overrides for these new classes - this needs cleaning up but I wanted to get the classes in first
llvm-svn: 332376
Btver2 - VCVTPH2PSYrm needs to double pump the AGU
Broadwell - missing VCVTPS2PH*mr stores extra latency
Allows us to remove the WriteCvtF2FSt conversion store class
llvm-svn: 332357
This fixes a couple of BtVer2 missing instructions that weren't been handled in the override.
NOTE: There are still a lot of overrides that still need cleaning up!
llvm-svn: 331770
I've created the necessary classes but there are still a lot of overrides that need cleaning up.
NOTE: The Znver1 model was missing some div/idiv variants in the instregex patterns and wasn't setting the resource cycles at all in the overrides.
llvm-svn: 331767
Split to support single/double for scalar, XMM and YMM/ZMM instructions - removing InstrRW overrides for these instructions.
Fixes Atom ADDSUBPD instruction and reclassifies VFPCLASS as WriteFCmp which is closer in behaviour.
llvm-svn: 331672
WriteFRcp/WriteFRsqrt are split to support scalar, XMM and YMM/ZMM instructions.
WriteFSqrt is split into single/double/long-double sizes and scalar, XMM, YMM and ZMM instructions.
This removes all InstrRW overrides for these instructions.
NOTE: There were a couple of typos in the Znver1 model - notably a 1cy throughput for SQRT that is highly unlikely and doesn't tally with Agner.
NOTE: I had to add Agner's numbers for several targets for WriteFSqrt80.
llvm-svn: 331629
Split off from SchedWriteFAdd for fp rounding/bit-manipulation instructions.
Fixes an issue on btver2 which only had the ymm version using the JSTC pipe instead of JFPA.
llvm-svn: 331515
This took a bit of extra work as on Intel targets the old (V)PSLLDrr/(V)PSLLDrm style instructions act differently - I ended up creating WriteVecShiftImm classes for XMM/YMM/ZMM vector shift by immediate and retaining WriteVecShift as the default (used only by MMX) plus WriteVecShiftX/WriteVecShiftY. X86SchedWriteWidths hides most of this thank goodness.
llvm-svn: 331472
Also retagged VDBPSADBW instructions as SchedWritePSADBW instead of SchedWriteVecIMul which matches the behaviour on SkylakeServer (the only thing that supports it...)
llvm-svn: 331445
Split off pinsr/pextr and extractps instructions.
(Mostly) fixes PR36887.
Note: It might be worth adding a WriteFInsertLd class as well in the future.
Differential Revision: https://reviews.llvm.org/D45929
llvm-svn: 330714
Split the fp and integer vector logical instruction scheduler classes - older CPUs especially often handled these on different pipes.
This unearthed a couple of things that are also handled in this patch:
(1) We were tagging avx512 fp logic ops as WriteFAdd, probably because of the lack of WriteFLogic
(2) SandyBridge had integer logic ops only using Port5, when afaict they can use Ports015.
(3) Cleaned up x86 FCHS/FABS scheduling as they are typically treated as fp logic ops.
Differential Revision: https://reviews.llvm.org/D45629
llvm-svn: 330480
Split VCMP/VMAX/VMIN instructions off to WriteFCmp and VCOMIS instructions off to WriteFCom instead of assuming they match WriteFAdd
Differential Revision: https://reviews.llvm.org/D45656
llvm-svn: 330179
Summary:
Cmov and setcc previously used WriteALU, but on Intel processors at least they are more restricted than basic ALU ops.
This patch adds new SchedWrites for them and removes the InstRWs. I had to leave some InstRWs for CMOVA/CMOVBE and SETA/SETBE because those have an extra uop relative to the other condition codes on Intel CPUs.
The test changes are due to fixing a missing ZnAGU dependency on the memory form of setcc.
Reviewers: RKSimon, andreadb, GGanesh
Reviewed By: RKSimon
Subscribers: GGanesh, llvm-commits
Differential Revision: https://reviews.llvm.org/D45380
llvm-svn: 329539
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
llvm-svn: 329304
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
llvm-svn: 329067
Summary:
It seems many CPUs don't implement this instruction as well as the other vector multiplies. Often using a multi uop flow. Silvermont in particular has a 7 uop flow with 11 cycle throughput. Sandy Bridge implements it as a single uop with 5 cycle latency and 1 cycle throughput. But Haswell and later use 2 uops with 10 cycle latency and 2 cycle throughput.
This patch adds a new X86SchedWritePair we can use to tag this instruction separately. I've provided correct information for Silvermont, Btver2, and Sandy Bridge. I've removed the InstRWs for SandyBridge. I've left Haswell/Broadwell/Skylake InstRWs in place because I wasn't sure how to account for the different load latency between 128 and 256 bits. I also left Znver1 InstRWs in place because the existing values don't match Agner's spreadsheet.
I also left a FIXME in the SandyBridge model because it being used for the "generic" model is too optimistic for the 256/512-bit versions since those are multiple uops on all known CPUs.
Reviewers: RKSimon, GGanesh, courbet
Reviewed By: RKSimon
Subscribers: gchatelet, gbedwell, andreadb, llvm-commits
Differential Revision: https://reviews.llvm.org/D44972
llvm-svn: 328914
These instructions have the memory operand before the register operand. So we need to put ReadDefault for all the load ops first. Then the ReadAfterLd
Differential Revision: https://reviews.llvm.org/D44838
llvm-svn: 328823
Similar to r328694. The number of micro opcodes should be 2 for those
instructions.
This was found when testing AVX code for BtVer2 using llvm-mca.
llvm-svn: 328698
The Jaguar backend natively supports 128-bit data types. Operations on YMM
registers are split into two COPs (complex operations). Each COP consumes a slot
in the dispatch group, and in the reorder buffer.
The scheduling model for Jaguar should mark those instructions as `let
NumMicroOps = 2`.
This was found when testing AVX code for BtVer2 using llvm-mca.
llvm-svn: 328694
Currently MOVMSK instructions use the WriteVecLogic class, which is a very poor choice given that MOVMSK involves a SSE->GPR transfer.
Differential Revision: https://reviews.llvm.org/D44924
llvm-svn: 328664
Currently CRC32 instructions use the WriteFAdd class, this patch splits them off into their own, at the moment it is still mostly just a duplicate of WriteFAdd but it can now be tweaked on a target by target basis.
Differential Revision: https://reviews.llvm.org/D44647
llvm-svn: 328582
Give the bit count instructions their own scheduler classes instead of forcing them into existing classes.
These were mostly overridden anyway, but I had to add in costs from Agner for silvermont and znver1 and the Fam16h SoG for btver2 (Jaguar).
Differential Revision: https://reviews.llvm.org/D44879
llvm-svn: 328566
Andrew V. Tischenko