[OpenMP] libomp: Add new experimental barrier: two-level distributed barrier

Two-level distributed barrier is a new experimental barrier designed
for Intel hardware that has better performance in so

[OpenMP] libomp: Add new experimental barrier: two-level distributed barrier

Two-level distributed barrier is a new experimental barrier designed
for Intel hardware that has better performance in some cases than the
default hyper barrier.

This barrier is designed to handle fine granularity parallelism where
barriers are used frequently with little compute and memory access
between barriers. There is no need to use it for codes with few
barriers and large granularity compute, or memory intensive
applications, as little difference will be seen between this barrier
and the default hyper barrier. This barrier is designed to work
optimally with a fixed number of threads, and has a significant setup
time, so should NOT be used in situations where the number of threads
in a team is varied frequently.

The two-level distributed barrier is off by default -- hyper barrier
is used by default. To use this barrier, you must set all barrier
patterns to use this type, because it will not work with other barrier
patterns. Thus, to turn it on, the following settings are required:

KMP_FORKJOIN_BARRIER_PATTERN=dist,dist
KMP_PLAIN_BARRIER_PATTERN=dist,dist
KMP_REDUCTION_BARRIER_PATTERN=dist,dist

Branching factors (set with KMP_FORKJOIN_BARRIER, KMP_PLAIN_BARRIER,
and KMP_REDUCTION_BARRIER) are ignored by the two-level distributed
barrier.

Patch fixed for ITTNotify disabled builds and non-x86 builds

Co-authored-by: Jonathan Peyton <[email protected]>
Co-authored-by: Vladislav Vinogradov <[email protected]>

Differential Revision: https://reviews.llvm.org/D103121

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Revert "[OpenMP] Add Two-level Distributed Barrier"

This reverts commit 25073a4ecfc9b2e3cb76776185e63bfdb094cd98.

This breaks non-x86 OpenMP builds for a while now. Until a solution is
ready to be

Revert "[OpenMP] Add Two-level Distributed Barrier"

This reverts commit 25073a4ecfc9b2e3cb76776185e63bfdb094cd98.

This breaks non-x86 OpenMP builds for a while now. Until a solution is
ready to be upstreamed we revert the feature and unblock those builds.
See:
https://reviews.llvm.org/rG25073a4ecfc9b2e3cb76776185e63bfdb094cd98#1005821
and
https://reviews.llvm.org/rG25073a4ecfc9b2e3cb76776185e63bfdb094cd98#1005821

The currently proposed fix (D104788) seems not to be ready yet:
https://reviews.llvm.org/D104788#2841928

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[OpenMP] Add Two-level Distributed Barrier

Two-level distributed barrier is a new experimental barrier designed
for Intel hardware that has better performance in some cases than the
default hyper ba

[OpenMP] Add Two-level Distributed Barrier

Two-level distributed barrier is a new experimental barrier designed
for Intel hardware that has better performance in some cases than the
default hyper barrier.

This barrier is designed to handle fine granularity parallelism where
barriers are used frequently with little compute and memory access
between barriers. There is no need to use it for codes with few
barriers and large granularity compute, or memory intensive
applications, as little difference will be seen between this barrier
and the default hyper barrier. This barrier is designed to work
optimally with a fixed number of threads, and has a significant setup
time, so should NOT be used in situations where the number of threads
in a team is varied frequently.

The two-level distributed barrier is off by default -- hyper barrier
is used by default. To use this barrier, you must set all barrier
patterns to use this type, because it will not work with other barrier
patterns. Thus, to turn it on, the following settings are required:

KMP_FORKJOIN_BARRIER_PATTERN=dist,dist
KMP_PLAIN_BARRIER_PATTERN=dist,dist
KMP_REDUCTION_BARRIER_PATTERN=dist,dist

Branching factors (set with KMP_FORKJOIN_BARRIER, KMP_PLAIN_BARRIER,
and KMP_REDUCTION_BARRIER) are ignored by the two-level distributed
barrier.

Differential Revision: https://reviews.llvm.org/D103121

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[OpenMP] Add support for Intel's umonitor/umwait

These changes add support for Intel's umonitor/umwait usage in wait
code, for architectures that support those intrinsic functions. Usage of
umonitor

[OpenMP] Add support for Intel's umonitor/umwait

These changes add support for Intel's umonitor/umwait usage in wait
code, for architectures that support those intrinsic functions. Usage of
umonitor/umwait is off by default, but can be turned on by setting the
KMP_USER_LEVEL_MWAIT environment variable.

Differential Revision: https://reviews.llvm.org/D91189

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Revert "[OpenMP] Add support for Intel's umonitor/umwait"

This reverts commit 9cfad5f9c5bfd985f1bc8b0954f58013c5236e58.

[OpenMP] Add support for Intel's umonitor/umwait

Patch by tlwilmar (Terry Wilmarth)

Differential Revision: https://reviews.llvm.org/D91189

Update more file headers across all of the LLVM projects in the monorepo
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that

Update more file headers across all of the LLVM projects in the monorepo
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351648

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Block library shutdown until unreaped threads finish spin-waiting

This change fixes possibly invalid access to the internal data structure during
library shutdown. In a heavily oversubscribed situa

Block library shutdown until unreaped threads finish spin-waiting

This change fixes possibly invalid access to the internal data structure during
library shutdown. In a heavily oversubscribed situation, the library shutdown
sequence can reach the point where resources are deallocated while there still
exist threads in their final spinning loop. The added loop in
__kmp_internal_end() checks if there are such busy-waiting threads and blocks
the shutdown sequence if that is the case. Two versions of kmp_wait_template()
are now used to minimize performance impact.

Patch by Hansang Bae

Differential Revision: https://reviews.llvm.org/D49452

llvm-svn: 337486

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Apply formatting changes

.clang-format's comments are removed and a (hopefully) final
set of formatting changes are applied.

Differential Revision: https://reviews.llvm.org/D38837
Differential Revi

Apply formatting changes

.clang-format's comments are removed and a (hopefully) final
set of formatting changes are applied.

Differential Revision: https://reviews.llvm.org/D38837
Differential Revision: https://reviews.llvm.org/D38920

llvm-svn: 316227

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Clang-format and whitespace cleanup of source code

This patch contains the clang-format and cleanup of the entire code base. Some
of clang-formats changes made the code look worse in places. A best

Clang-format and whitespace cleanup of source code

This patch contains the clang-format and cleanup of the entire code base. Some
of clang-formats changes made the code look worse in places. A best effort was
made to resolve the bulk of these problems, but many remain. Most of the
problems were mangling line-breaks and tabbing of comments.

Patch by Terry Wilmarth

Differential Revision: https://reviews.llvm.org/D32659

llvm-svn: 302929

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Remove unused wait/release code.

Cleanup - unused code removal.
TODO: consider to remove (replace with flag class methods)
also kmp_wait_64 and kmp_release_64 routines.

Patch by Andrey Churbanov

D

Remove unused wait/release code.

Cleanup - unused code removal.
TODO: consider to remove (replace with flag class methods)
also kmp_wait_64 and kmp_release_64 routines.

Patch by Andrey Churbanov

Differential Revision: http://reviews.llvm.org/D21332

llvm-svn: 272697

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Comments only: removing the Revision and Date svn variables from the top of all the source files.

llvm-svn: 227207

I apologise in advance for the size of this check-in. At Intel we do
understand that this is not friendly, and are working to change our
internal code-development to make it easier to make developmen

I apologise in advance for the size of this check-in. At Intel we do
understand that this is not friendly, and are working to change our
internal code-development to make it easier to make development
features available more frequently and in finer (more functional)
chunks. Unfortunately we haven't got that in place yet, and unpicking
this into multiple separate check-ins would be non-trivial, so please
bear with me on this one. We should be better in the future.

Apologies over, what do we have here?

GGC 4.9 compatibility
--------------------
* We have implemented the new entrypoints used by code compiled by GCC
4.9 to implement the same functionality in gcc 4.8. Therefore code
compiled with gcc 4.9 that used to work will continue to do so.
However, there are some other new entrypoints (associated with task
cancellation) which are not implemented. Therefore user code compiled
by gcc 4.9 that uses these new features will not link against the LLVM
runtime. (It remains unclear how to handle those entrypoints, since
the GCC interface has potentially unpleasant performance implications
for join barriers even when cancellation is not used)

--- new parallel entry points ---
new entry points that aren't OpenMP 4.0 related
These are implemented fully :-
GOMP_parallel_loop_dynamic()
GOMP_parallel_loop_guided()
GOMP_parallel_loop_runtime()
GOMP_parallel_loop_static()
GOMP_parallel_sections()
GOMP_parallel()

--- cancellation entry points ---
Currently, these only give a runtime error if OMP_CANCELLATION is true
because our plain barriers don't check for cancellation while waiting
GOMP_barrier_cancel()
GOMP_cancel()
GOMP_cancellation_point()
GOMP_loop_end_cancel()
GOMP_sections_end_cancel()

--- taskgroup entry points ---
These are implemented fully.
GOMP_taskgroup_start()
GOMP_taskgroup_end()

--- target entry points ---
These are empty (as they are in libgomp)
GOMP_target()
GOMP_target_data()
GOMP_target_end_data()
GOMP_target_update()
GOMP_teams()

Improvements in Barriers and Fork/Join
--------------------------------------
* Barrier and fork/join code is now in its own file (which makes it
easier to understand and modify).
* Wait/release code is now templated and in its own file; suspend/resume code is also templated
* There's a new, hierarchical, barrier, which exploits the
cache-hierarchy of the Intel(r) Xeon Phi(tm) coprocessor to improve
fork/join and barrier performance.

***BEWARE*** the new source files have *not* been added to the legacy
Cmake build system. If you want to use that fixes wil be required.

Statistics Collection Code
--------------------------
* New code has been added to collect application statistics (if this
is enabled at library compile time; by default it is not). The
statistics code itself is generally useful, the lightweight timing
code uses the X86 rdtsc instruction, so will require changes for other
architectures.
The intent of this code is not for users to tune their codes but
rather
1) For timing code-paths inside the runtime
2) For gathering general properties of OpenMP codes to focus attention
on which OpenMP features are most used.

Nested Hot Teams
----------------
* The runtime now maintains more state to reduce the overhead of
creating and destroying inner parallel teams. This improves the
performance of code that repeatedly uses nested parallelism with the
same resource allocation. Set the new KMP_HOT_TEAMS_MAX_LEVEL
envirable to a depth to enable this (and, of course, OMP_NESTED=true
to enable nested parallelism at all).

Improved Intel(r) VTune(Tm) Amplifier support
---------------------------------------------
* The runtime provides additional information to Vtune via the
itt_notify interface to allow it to display better OpenMP specific
analyses of load-imbalance.

Support for OpenMP Composite Statements
---------------------------------------
* Implement new entrypoints required by some of the OpenMP 4.1
composite statements.

Improved ifdefs
---------------
* More separation of concepts ("Does this platform do X?") from
platforms ("Are we compiling for platform Y?"), which should simplify
future porting.


ScaleMP* contribution
---------------------
Stack padding to improve the performance in their environment where
cross-node coherency is managed at the page level.

Redesign of wait and release code
---------------------------------
The code is simplified and performance improved.

Bug Fixes
---------
*Fixes for Windows multiple processor groups.
*Fix Fortran module build on Linux: offload attribute added.
*Fix entry names for distribute-parallel-loop construct to be consistent with the compiler codegen.
*Fix an inconsistent error message for KMP_PLACE_THREADS environment variable.

llvm-svn: 219214

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