Enable registration of multiple exegesis targets at once. Use idiomatic approach to defining target select macros, but leave code in the llvm-mca sub-directories for now.
This is a stepping stone towards allowing llvm-exegesis benchmarking via simulator or testing in non-target dependent tests.
Differential Revision: https://reviews.llvm.org/D133605
We were using the native triple to parse the benchmarks. Use the triple
from the benchmarks file.
Right now this still only allows analyzing files produced by the current
target until D133605 is in.
This also makes the `Analysis` class much less ad-hoc.
Differential Revision: https://reviews.llvm.org/D133697
llvm-exegesis is rather odd in the LLVM ecosystem in code is selectively compiled based on the native machine. LLVM is cross compiler by default, so this stands out as odd. It's also less then helpful when working on code for a target other than your native dev environment.
This change only changes the build setup. A later change will enable -march support to allow actual benchmarking under e.g. simulators in a cross compilation environment.
Differential Revision: https://reviews.llvm.org/D133150
This moves the registry higher in the LLVM library dependency stack.
Every client of the target registry needs to link against MC anyway to
actually use the target, so we might as well move this out of Support.
This allows us to ensure that Support doesn't have includes from MC/*.
Differential Revision: https://reviews.llvm.org/D111454
Currently native clusterization simply groups all benchmarks
by the opcode of key instruction, but that is suboptimal in certain cases,
e.g. where we can already tell that the particular instructions
already resolve into different sched classes.
I really needed this, like, factually, yesterday,
when verifying dependency breaking idioms for AMD Zen 3 scheduler model.
Consider the following example:
```
$ ./bin/llvm-exegesis --mode=inverse_throughput --snippets-file=/tmp/snippet.s --num-repetitions=1000000 --repetition-mode=duplicate
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-4a7e50.o
---
mode: inverse_throughput
key:
instructions:
- 'VPXORYrr YMM0 YMM0 YMM0'
config: ''
register_initial_values: []
cpu_name: znver3
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 1000000
measurements:
- { key: inverse_throughput, value: 0.31025, per_snippet_value: 0.31025 }
error: ''
info: ''
assembled_snippet: C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C5FDEFC0C3
...
```
What does it tell us?
So wait, it can only execute ~3 x86 AVX YMM PXOR zero-idioms per cycle?
That doesn't seem right. That's even less than there are pipes supporting this type of op.
Now, second example:
```
$ ./bin/llvm-exegesis --mode=inverse_throughput --snippets-file=/tmp/snippet.s --num-repetitions=1000000 --repetition-mode=loop
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-2418b5.o
---
mode: inverse_throughput
key:
instructions:
- 'VPXORYrr YMM0 YMM0 YMM0'
config: ''
register_initial_values: []
cpu_name: znver3
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 1000000
measurements:
- { key: inverse_throughput, value: 1.00011, per_snippet_value: 1.00011 }
error: ''
info: ''
assembled_snippet: 49B80800000000000000C5FDEFC0C5FDEFC04983C0FF75F2C3
...
```
Now that's just worse. Due to the looping, the throughput completely plummeted,
and now we can only do a single instruction/cycle!?
That's not great.
And final example:
```
$ ./bin/llvm-exegesis --mode=inverse_throughput --snippets-file=/tmp/snippet.s --num-repetitions=1000000 --repetition-mode=loop --loop-body-size=1000
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-c402e2.o
---
mode: inverse_throughput
key:
instructions:
- 'VPXORYrr YMM0 YMM0 YMM0'
config: ''
register_initial_values: []
cpu_name: znver3
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 1000000
measurements:
- { key: inverse_throughput, value: 0.167087, per_snippet_value: 0.167087 }
error: ''
info: ''
assembled_snippet: 49B80800000000000000C5FDEFC0C5FDEFC04983C0FF75F2C3
...
```
So if we merge the previous two approaches, do duplicate this single-instruction snippet 1000x
(loop-body-size/instruction count in snippet), and run a loop with 1000 iterations
over that duplicated/unrolled snippet, the measured throughput goes through the roof,
up to 5.9 instructions/cycle, which finally tells us that this idiom is zero-cycle!
Reviewed By: courbet
Differential Revision: https://reviews.llvm.org/D102522
CommandLine.h is indirectly included in ~50% of TUs when building
clang, and VirtualFileSystem.h is large.
(Already remarked by jhenderson on D70769.)
No behavior change.
Differential Revision: https://reviews.llvm.org/D100957
Some instructions defined in table-gen files sets usesCustomInserter
bit, which means it has to be lowered by target code and isn't actually
valid instruction at MC level. So we should treat them like pseudo
instructions.
Reviewed By: gchatelet
Differential Revision: https://reviews.llvm.org/D94898
All these potential null pointer dereferences are reported by my static analyzer for null smart pointer dereferences, which has a different implementation from `alpha.cplusplus.SmartPtr`.
The checked pointers in this patch are initialized by Target::createXXX functions. When the creator function pointer is not correctly set, a null pointer will be returned, or the creator function may originally return a null pointer.
Some of them may not make sense as they may be checked before entering the function, but I fixed them all in this patch. I submit this fix because 1) similar checks are found in some other places in the LLVM codebase for the same return value of the function; and, 2) some of the pointers are dereferenced before they are checked, which may definitely trigger a null pointer dereference if the return value is nullptr.
Reviewed By: tejohnson, MaskRay, jpienaar
Differential Revision: https://reviews.llvm.org/D91410
This is mostly for the benefit of the LBR latency mode.
Right now, it performs no checking. If this is run on non-supported hardware, it will produce all zeroes for latency.
Differential Revision: https://reviews.llvm.org/D85254
New change: Updated lit.local.cfg to use pass the right argument to llvm-exegesis to actually request the LBR mode.
Differential Revision: https://reviews.llvm.org/D88670
This reverts commit 4fcd1a8e65 as
`llvm/test/tools/llvm-exegesis/X86/lbr/mov-add.s` failed on hosts
without LBR supported if the build has LIBPFM enabled. On that host,
`perf_event_open` fails with `EOPNOTSUPP` on LBR config. That change's
basic assumption
> If this is run on a non-supported hardware, it will produce all zeroes for latency.
could not stand as `perf_event_open` system call will fail if the
underlying hardware really don't have LBR supported.
This is mostly for the benefit of the LBR latency mode.
Right now, it performs no checking. If this is run on non-supported hardware, it will produce all zeroes for latency.
Differential Revision: https://reviews.llvm.org/D85254
Starting with Skylake, the LBR contains the precise number of cycles between the two
consecutive branches.
Making use of this will hopefully make the measurements more precise than the
existing methods of using RDTSC.
Differential Revision: https://reviews.llvm.org/D77422
New change: check for existence of field `cycles` in perf_branch_entry before enabling this mode.
This should prevent compilation errors when building for older kernel whose headers don't support it.
From @erichkeane:
```
This patch doesn't seem to build for me:
/iusers/ekeane1/workspaces/llvm-project/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp: In function ‘llvm::Error llvm::exegesis::parseDataBuffer(const char*, size_t, const void*, const void*, llvm::SmallVector<long int, 4>*)’:
/iusers/ekeane1/workspaces/llvm-project/llvm/tools/llvm-exegesis/lib/X86/X86Counter.cpp:99:37: error: ‘struct perf_branch_entry’ has no member named ‘cycles’
CycleArray->push_back(Entry.cycles);
I'm on RHEL7, so I have kernel 3.10, so it doesn't have 'cycles'.
According ot this: https://elixir.bootlin.com/linux/v4.3/source/include/uapi/linux/perf_event.h#L963 kernel 4.3 is the first time that 'cycles' appeared in this structure.
```
Starting with Skylake, the LBR contains the precise number of cycles between the two
consecutive branches.
Making use of this will hopefully make the measurements more precise than the
existing methods of using RDTSC.
Differential Revision: https://reviews.llvm.org/D77422
LBR contains (up to) 16 entries for last x branches and the X86LBRCounter (from D77422) should be able to return all those.
Currently, it just returns the latest entry, which could lead to mis-leading measurements.
This patch aslo changes the LatencyBenchmarkRunner to accommodate multi-value readings.
https://reviews.llvm.org/D81050
Summary:
As noted in documentation, different repetition modes have different trade-offs:
> .. option:: -repetition-mode=[duplicate|loop]
>
> Specify the repetition mode. `duplicate` will create a large, straight line
> basic block with `num-repetitions` copies of the snippet. `loop` will wrap
> the snippet in a loop which will be run `num-repetitions` times. The `loop`
> mode tends to better hide the effects of the CPU frontend on architectures
> that cache decoded instructions, but consumes a register for counting
> iterations.
Indeed. Example:
>>! In D74156#1873657, @lebedev.ri wrote:
> At least for `CMOV`, i'm seeing wildly different results
> | | Latency | RThroughput |
> | duplicate | 1 | 0.8 |
> | loop | 2 | 0.6 |
> where latency=1 seems correct, and i'd expect the througput to be close to 1/2 (since there are two execution units).
This isn't great for analysis, at least for schedule model development.
As discussed in excruciating detail in
>>! In D74156#1924514, @gchatelet wrote:
>>>! In D74156#1920632, @lebedev.ri wrote:
>> ... did that explanation of the question i'm having made any sense?
>
> Thx for digging in the conversation !
> Ok it makes more sense now.
>
> I discussed it a bit with @courbet:
> - We want the analysis tool to stay simple so we'd rather not make it knowledgeable of the repetition mode.
> - We'd like to still be able to select either repetition mode to dig into special cases
>
> So we could add a third `min` repetition mode that would run both and take the minimum. It could be the default option.
> Would you have some time to look what it would take to add this third mode?
there appears to be an agreement that it is indeed sub-par,
and that we should provide an optional, measurement (not analysis!) -time
way to rectify the situation.
However, the solutions isn't entirely straight-forward.
We can just add an actual 'multiplexer' `MinSnippetRepetitor`, because
if we just concatenate snippets produced by `DuplicateSnippetRepetitor`
and `LoopSnippetRepetitor` and run+measure that, the measurement will
naturally be different from what we'd get by running+measuring
them separately and taking the min.
([[ https://www.wolframalpha.com/input/?i=%28x%2By%29%2F2+%21%3D+min%28x%2C+y%29 | `time(D+L)/2 != min(time(D), time(L))` ]])
Also, it seems best to me to have a single snippet instead of generating
a snippet per repetition mode, since the only difference here is that the
loop repetition mode reserves one register for loop counter.
As far as i can tell, we can either teach `BenchmarkRunner::runConfiguration()`
to produce a single report given multiple repetitors (as in the patch),
or do that one layer higher - don't modify `BenchmarkRunner::runConfiguration()`,
produce multiple reports, don't actually print each one, but aggregate them somehow
and only print the final one.
Initially i've gone ahead with the latter approach, but it didn't look like a natural fit;
the former (as in the diff) does seem like a better fit to me.
There's also a question of the test coverage. It sure currently does work here:
```
$ ./bin/llvm-exegesis --opcode-name=CMOV64rr --mode=inverse_throughput --repetition-mode=duplicate
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-8fb949.o
---
mode: inverse_throughput
key:
instructions:
- 'CMOV64rr RAX RAX R11 i_0x0'
- 'CMOV64rr RBP RBP R15 i_0x0'
- 'CMOV64rr RBX RBX RBX i_0x0'
- 'CMOV64rr RCX RCX RBX i_0x0'
- 'CMOV64rr RDI RDI R10 i_0x0'
- 'CMOV64rr RDX RDX RAX i_0x0'
- 'CMOV64rr RSI RSI RAX i_0x0'
- 'CMOV64rr R8 R8 R8 i_0x0'
- 'CMOV64rr R9 R9 RDX i_0x0'
- 'CMOV64rr R10 R10 RBX i_0x0'
- 'CMOV64rr R11 R11 R14 i_0x0'
- 'CMOV64rr R12 R12 R9 i_0x0'
- 'CMOV64rr R13 R13 R12 i_0x0'
- 'CMOV64rr R14 R14 R15 i_0x0'
- 'CMOV64rr R15 R15 R13 i_0x0'
config: ''
register_initial_values:
- 'RAX=0x0'
- 'R11=0x0'
- 'EFLAGS=0x0'
- 'RBP=0x0'
- 'R15=0x0'
- 'RBX=0x0'
- 'RCX=0x0'
- 'RDI=0x0'
- 'R10=0x0'
- 'RDX=0x0'
- 'RSI=0x0'
- 'R8=0x0'
- 'R9=0x0'
- 'R14=0x0'
- 'R12=0x0'
- 'R13=0x0'
cpu_name: bdver2
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:
- { key: inverse_throughput, value: 0.819, per_snippet_value: 12.285 }
error: ''
info: instruction has tied variables, using static renaming.
assembled_snippet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
...
$ ./bin/llvm-exegesis --opcode-name=CMOV64rr --mode=inverse_throughput --repetition-mode=loop
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-051eb3.o
---
mode: inverse_throughput
key:
instructions:
- 'CMOV64rr RAX RAX R11 i_0x0'
- 'CMOV64rr RBP RBP RSI i_0x0'
- 'CMOV64rr RBX RBX R9 i_0x0'
- 'CMOV64rr RCX RCX RSI i_0x0'
- 'CMOV64rr RDI RDI RBP i_0x0'
- 'CMOV64rr RDX RDX R9 i_0x0'
- 'CMOV64rr RSI RSI RDI i_0x0'
- 'CMOV64rr R9 R9 R12 i_0x0'
- 'CMOV64rr R10 R10 R11 i_0x0'
- 'CMOV64rr R11 R11 R9 i_0x0'
- 'CMOV64rr R12 R12 RBP i_0x0'
- 'CMOV64rr R13 R13 RSI i_0x0'
- 'CMOV64rr R14 R14 R14 i_0x0'
- 'CMOV64rr R15 R15 R10 i_0x0'
config: ''
register_initial_values:
- 'RAX=0x0'
- 'R11=0x0'
- 'EFLAGS=0x0'
- 'RBP=0x0'
- 'RSI=0x0'
- 'RBX=0x0'
- 'R9=0x0'
- 'RCX=0x0'
- 'RDI=0x0'
- 'RDX=0x0'
- 'R12=0x0'
- 'R10=0x0'
- 'R13=0x0'
- 'R14=0x0'
- 'R15=0x0'
cpu_name: bdver2
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:
- { key: inverse_throughput, value: 0.6083, per_snippet_value: 8.5162 }
error: ''
info: instruction has tied variables, using static renaming.
assembled_snippet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
...
$ ./bin/llvm-exegesis --opcode-name=CMOV64rr --mode=inverse_throughput --repetition-mode=min
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-c7a47d.o
Check generated assembly with: /usr/bin/objdump -d /tmp/snippet-2581f1.o
---
mode: inverse_throughput
key:
instructions:
- 'CMOV64rr RAX RAX R11 i_0x0'
- 'CMOV64rr RBP RBP R10 i_0x0'
- 'CMOV64rr RBX RBX R10 i_0x0'
- 'CMOV64rr RCX RCX RDX i_0x0'
- 'CMOV64rr RDI RDI RAX i_0x0'
- 'CMOV64rr RDX RDX R9 i_0x0'
- 'CMOV64rr RSI RSI RAX i_0x0'
- 'CMOV64rr R9 R9 RBX i_0x0'
- 'CMOV64rr R10 R10 R12 i_0x0'
- 'CMOV64rr R11 R11 RDI i_0x0'
- 'CMOV64rr R12 R12 RDI i_0x0'
- 'CMOV64rr R13 R13 RDI i_0x0'
- 'CMOV64rr R14 R14 R9 i_0x0'
- 'CMOV64rr R15 R15 RBP i_0x0'
config: ''
register_initial_values:
- 'RAX=0x0'
- 'R11=0x0'
- 'EFLAGS=0x0'
- 'RBP=0x0'
- 'R10=0x0'
- 'RBX=0x0'
- 'RCX=0x0'
- 'RDX=0x0'
- 'RDI=0x0'
- 'R9=0x0'
- 'RSI=0x0'
- 'R12=0x0'
- 'R13=0x0'
- 'R14=0x0'
- 'R15=0x0'
cpu_name: bdver2
llvm_triple: x86_64-unknown-linux-gnu
num_repetitions: 10000
measurements:
- { key: inverse_throughput, value: 0.6073, per_snippet_value: 8.5022 }
error: ''
info: instruction has tied variables, using static renaming.
assembled_snippet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
...
```
but i open to suggestions as to how test that.
I also have gone with the suggestion to default to this new mode.
This was irking me for some time, so i'm happy to finally see progress here.
Looking forward to feedback.
Reviewers: courbet, gchatelet
Reviewed By: courbet, gchatelet
Subscribers: mstojanovic, RKSimon, llvm-commits, courbet, gchatelet
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D76921
Summary:
Currently, we only have nice exploration for LEA instruction,
while for the rest, we rely on `randomizeUnsetVariables()`
to sometimes generate something interesting.
While that works, it isn't very reliable in coverage :)
Here, i'm making an assumption that while we may want to explore
multi-instruction configs, we are most interested in the
characteristics of the main instruction we were asked about.
Which we can do, by taking the existing `randomizeMCOperand()`,
and turning it on it's head - instead of relying on it to randomly fill
one of the interesting values, let's pregenerate all the possible interesting
values for the variable, and then generate as much `InstructionTemplate`
combinations of these possible values for variables as needed/possible.
Of course, that requires invasive changes to no longer pass just the
naked `Instruction`, but sometimes partially filled `InstructionTemplate`.
As it can be seen from the test, this allows us to explore
`X86::OperandType::OPERAND_COND_CODE` for instructions
that take such an operand.
I'm hoping this will greatly simplify exploration.
Reviewers: courbet, gchatelet
Reviewed By: gchatelet
Subscribers: orodley, mgorny, sdardis, tschuett, jrtc27, atanasyan, mstojanovic, andreadb, RKSimon, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D74156
Followup to D74085.
Replace the use of `report_fatal_error()` with returning the error to
`llvm-exegesis.cpp` and handling it there.
To facilitate this, a new `Error` type has been added which is only used
to log errors to the yaml output.
Differential Revision: https://reviews.llvm.org/D74215
Summary: Commit 141915963b was reverted in
abe01e17f6 because it broke builds testing
without libpfm. A preparatory commit <commit_sha1> was added to enable
this recommit.
Original commit message:
Followup to D74085.
Replace the use of `report_fatal_error()` with returning the error to
`llvm-exegesis.cpp` and handling it there.
Differential Revision: https://reviews.llvm.org/D74113
Summary: Commit b3576f60eb was reverted in
abe01e17f6 because it broke builds testing
without libpfm. A preparatory commit <commit_sha1> was added to enable
this recommit.
Original commit message:
Fix inconsistencies in error reporting created by mixing
`report_fatal_error()` and `ExitOnErr()`, and add additional information
to the error message to make it more user friendly. Minimize the use
`report_fatal_error()` because it's meant for use in very rare cases and
it results in low information density of the error messages.
Summary of the new design:
* For command line argument errors output `llvm-exegesis: <error_message>`,
which is consistent with the error output format emitted by the backend
which checks correctness of the command line arguments.
* For other errors the format `llvm-exegesis error: <error_message>` is used.
** If the error occurred during file access `<error_message>` will have
of two parts: `'<file_name>': <rest_of_the_error_message>`
Differential Revision: https://reviews.llvm.org/D74085
All errors of type `Failure` are `StringError`s. In order for exit code
mapping to detect that specifically a clustering error has occurred it
needs to have a different type.
This patch also prepares D74085 where termination `report_fatal_error()`
will be replaced with emitting `StringError`s.
Differential Revision: https://reviews.llvm.org/D74124
It broke e.g. all tests under tools/llvm-exegesis/X86/ when libpfm is
not available, see comment on D74085.
This reverts commit b3576f60eb and
141915963b.
Followup to D74085.
Replace the use of `report_fatal_error()` with returning the error to
`llvm-exegesis.cpp` and handling it there.
Differential Revision: https://reviews.llvm.org/D74113
Fix inconsistencies in error reporting created by mixing
`report_fatal_error()` and `ExitOnErr()`, and add additional information
to the error message to make it more user friendly. Minimize the use
`report_fatal_error()` because it's meant for use in very rare cases and
it results in low information density of the error messages.
Summary of the new design:
* For command line argument errors output `llvm-exegesis: <error_message>`,
which is consistent with the error output format emitted by the backend
which checks correctness of the command line arguments.
* For other errors the format `llvm-exegesis error: <error_message>` is used.
** If the error occurred during file access `<error_message>` will have
of two parts: `'<file_name>': <rest_of_the_error_message>`
Differential Revision: https://reviews.llvm.org/D74085
Check if the appropriate counters for the specified mode are defined on
the target. This is checked before any other work is done.
Differential Revision: https://reviews.llvm.org/D71927
Summary:
This adds a `-max-configs-per-opcode` option to limit the number of
configs per opcode.
Reviewers: gchatelet
Subscribers: tschuett, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D68642
llvm-svn: 374054
Summary:
Before this change the Executable function was made by duplicating the
snippet. This change adds a --repetion-mode={loop|duplicate} flag that
allows choosing between this behaviour and wrapping the snippet instructions
in a loop.
The new mode can help measurements when the snippet fits in the DSB by
short-cirtcuiting decoding. The loop adds a dec + jmp to the measurements, but
since these are not part of the critical path, they execute in parallel
with the measured code and do not impact measurements in practice.
Overview of the change:
- New SnippetRepetitor abstraction that handles repeating the snippet.
The assembler delegates repeating the instructions to this class.
- ExegesisTarget learns how to decrement loop counter and jump.
- Some refactoring of the assembler into FunctionFiller/BasicBlockFiller.
Reviewers: gchatelet
Subscribers: mgorny, tschuett, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D68125
llvm-svn: 373083
Summary: This helps building internal tools on top of the library.
Reviewers: gchatelet
Subscribers: tschuett, llvm-commits, bdb, ondrasej
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D62239
llvm-svn: 361385
Wanted to check if inablility to measure latency of CMOV32rm
is a regression from D60041 / D60138, but unable to do that
because the llvm-exegesis-{8,9} from debian sid fails
with that cryptic, unhelpful error.
I suspect this will be a better error.
llvm-svn: 357900
Summary:
This is an alternative to D59539.
Let's suppose we have measured 4 different opcodes, and got: `0.5`, `1.0`, `1.5`, `2.0`.
Let's suppose we are using `-analysis-clustering-epsilon=0.5`.
By default now we will start processing the `0.5` point, find that `1.0` is it's neighbor, add them to a new cluster.
Then we will notice that `1.5` is a neighbor of `1.0` and add it to that same cluster.
Then we will notice that `2.0` is a neighbor of `1.5` and add it to that same cluster.
So all these points ended up in the same cluster.
This may or may not be a correct implementation of dbscan clustering algorithm.
But this is rather horribly broken for the reasons of comparing the clusters with the LLVM sched data.
Let's suppose all those opcodes are currently in the same sched cluster.
If i specify `-analysis-inconsistency-epsilon=0.5`, then no matter
the LLVM values this cluster will **never** match the LLVM values,
and thus this cluster will **always** be displayed as inconsistent.
The solution is obviously to split off some of these opcodes into different sched cluster.
But how do i do that? Out of 4 opcodes displayed in the inconsistency report,
which ones are the "bad ones"? Which ones are the most different from the checked-in data?
I'd need to go in to the `.yaml` and look it up manually.
The trivial solution is to, when creating clusters, don't use the full dbscan algorithm,
but instead "pick some unclustered point, pick all unclustered points that are it's neighbor,
put them all into a new cluster, repeat". And just so as it happens, we can arrive
at that algorithm by not performing the "add neighbors of a neighbor to the cluster" step.
But that won't work well once we teach analyze mode to operate in on-1D mode
(i.e. on more than a single measurement type at a time), because the clustering would
depend on the order of the measurements.
Instead, let's just create a single cluster per opcode, and put all the points of that opcode into said cluster.
And simultaneously check that every point in that cluster is a neighbor of every other point in the cluster,
and if they are not, the cluster (==opcode) is unstable.
This is //yet another// step to bring me closer to being able to continue cleanup of bdver2 sched model..
Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=40880 | PR40880 ]].
Reviewers: courbet, gchatelet
Reviewed By: courbet
Subscribers: tschuett, jdoerfert, RKSimon, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59820
llvm-svn: 357152
Results in much nicer -help output:
```
$ ./bin/llvm-exegesis -help
USAGE: llvm-exegesis [options]
OPTIONS:
Color Options:
-color - Use colors in output (default=autodetect)
General options:
-enable-cse-in-irtranslator - Should enable CSE in irtranslator
-enable-cse-in-legalizer - Should enable CSE in Legalizer
Generic Options:
-help - Display available options (-help-hidden for more)
-help-list - Display list of available options (-help-list-hidden for more)
-version - Display the version of this program
llvm-exegesis analysis options:
-analysis-clustering-epsilon=<number> - dbscan epsilon for benchmark point clustering
-analysis-clusters-output-file=<string> -
-analysis-display-unstable-clusters - if there is more than one benchmark for an opcode, said benchmarks may end up not being clustered into the same cluster if the measured performance characteristics are different. by default all such opcodes are filtered out. this flag will instead show only such unstable opcodes
-analysis-inconsistencies-output-file=<string> -
-analysis-inconsistency-epsilon=<number> - epsilon for detection of when the cluster is different from the LLVM schedule profile values
-analysis-numpoints=<uint> - minimum number of points in an analysis cluster
llvm-exegesis benchmark options:
-ignore-invalid-sched-class - ignore instructions that do not define a sched class
-mode=<value> - the mode to run
=latency - Instruction Latency
=inverse_throughput - Instruction Inverse Throughput
=uops - Uop Decomposition
=analysis - Analysis
-num-repetitions=<uint> - number of time to repeat the asm snippet
-opcode-index=<int> - opcode to measure, by index
-opcode-name=<string> - comma-separated list of opcodes to measure, by name
-snippets-file=<string> - code snippets to measure
llvm-exegesis options:
-benchmarks-file=<string> - File to read (analysis mode) or write (latency/uops/inverse_throughput modes) benchmark results. “-” uses stdin/stdout.
-mcpu=<string> - cpu name to use for pfm counters, leave empty to autodetect
```
llvm-svn: 356364
This patch removes hidden codegen flag -print-schedule effectively reverting the
logic originally committed as r300311
(https://llvm.org/viewvc/llvm-project?view=revision&revision=300311).
Flag -print-schedule was originally introduced by r300311 to address PR32216
(https://bugs.llvm.org/show_bug.cgi?id=32216). That bug was about adding "Better
testing of schedule model instruction latencies/throughputs".
These days, we can use llvm-mca to test scheduling models. So there is no longer
a need for flag -print-schedule in LLVM. The main use case for PR32216 is
now addressed by llvm-mca.
Flag -print-schedule is mainly used for debugging purposes, and it is only
actually used by x86 specific tests. We already have extensive (latency and
throughput) tests under "test/tools/llvm-mca" for X86 processor models. That
means, most (if not all) existing -print-schedule tests for X86 are redundant.
When flag -print-schedule was first added to LLVM, several files had to be
modified; a few APIs gained new arguments (see for example method
MCAsmStreamer::EmitInstruction), and MCSubtargetInfo/TargetSubtargetInfo gained
a couple of getSchedInfoStr() methods.
Method getSchedInfoStr() had to originally work for both MCInst and
MachineInstr. The original implmentation of getSchedInfoStr() introduced a
subtle layering violation (reported as PR37160 and then fixed/worked-around by
r330615).
In retrospect, that new API could have been designed more optimally. We can
always query MCSchedModel to get the latency and throughput. More importantly,
the "sched-info" string should not have been generated by the subtarget.
Note, r317782 fixed an issue where "print-schedule" didn't work very well in the
presence of inline assembly. That commit is also reverted by this change.
Differential Revision: https://reviews.llvm.org/D57244
llvm-svn: 353043
Summary:
Up until the point i have looked in the source, i didn't even understood that
i can disable 'cluster' output. I have always silenced it via ` &> /dev/null`.
(And hoped it wasn't contributing much of the run time.)
While i expect that it has it's use-cases i never once needed it so far.
If i forget to silence it, console is completely flooded with that output.
How about not expecting users to opt-out of analyses,
but to explicitly specify the analyses that should be performed?
Reviewers: courbet, gchatelet
Reviewed By: courbet
Subscribers: tschuett, RKSimon, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D57648
llvm-svn: 353021
Philip Reames