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libgomp.texi: Reverse-offload updates

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libgomp/
	* libgomp.texi (5.0 Impl. Status): Update 'requires' and 'ancestor'.
	(GCN): Add item about 'omp requires'.
	(nvptx): Likewise; add item about reverse offload.
This commit is contained in:
Tobias Burnus 2023-02-01 12:19:27 +01:00
parent 3cef9dca57
commit eda38850a7
1 changed files with 19 additions and 7 deletions
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26
libgomp/libgomp.texi
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@ -192,8 +192,8 @@ The OpenMP 4.5 specification is fully supported.
env variable @tab Y @tab
@item Nested-parallel changes to @emph{max-active-levels-var} ICV @tab Y @tab
@item @code{requires} directive @tab P
@tab complete but no non-host devices provides @code{unified_address},
@code{unified_shared_memory} or @code{reverse_offload}
@tab complete but no non-host devices provides @code{unified_address} or
@code{unified_shared_memory}
@item @code{teams} construct outside an enclosing target region @tab Y @tab
@item Non-rectangular loop nests @tab P @tab Full support for C/C++, partial for Fortran
@item @code{!=} as relational-op in canonical loop form for C/C++ @tab Y @tab
@ -228,7 +228,7 @@ The OpenMP 4.5 specification is fully supported.
@item @code{allocate} clause @tab P @tab Initial support
@item @code{use_device_addr} clause on @code{target data} @tab Y @tab
@item @code{ancestor} modifier on @code{device} clause
@tab Y @tab See comment for @code{requires}
@tab Y @tab Host fallback with GCN devices
@item Implicit declare target directive @tab Y @tab
@item Discontiguous array section with @code{target update} construct
@tab N @tab
@ -288,7 +288,7 @@ The OpenMP 4.5 specification is fully supported.
@code{append_args} @tab N @tab
@item @code{dispatch} construct @tab N @tab
@item device-specific ICV settings with environment variables @tab Y @tab
@item @code{assume} directive @tab Y @tab
@item @code{assume} and @code{assumes} directives @tab Y @tab
@item @code{nothing} directive @tab Y @tab
@item @code{error} directive @tab Y @tab
@item @code{masked} construct @tab Y @tab
@ -351,7 +351,7 @@ The OpenMP 4.5 specification is fully supported.
to address of matching mapped list item per 5.1, Sect. 2.21.7.2 @tab N @tab
@item For Fortran, diagnose placing declarative before/between @code{USE},
@code{IMPORT}, and @code{IMPLICIT} as invalid @tab N @tab
@item Optional comma beween directive and clause in the @code{#pragma} form @tab Y @tab
@item Optional comma between directive and clause in the @code{#pragma} form @tab Y @tab
@item @code{indirect} clause in @code{declare target} @tab N @tab
@item @code{device_type(nohost)}/@code{device_type(host)} for variables @tab N @tab
@end multitable
@ -3956,7 +3956,7 @@ same context.
@section First invocation: OpenACC library API
In this second use case (see below), a function in the OpenACC library is
called prior to any of the functions in the CUBLAS library. More specificially,
called prior to any of the functions in the CUBLAS library. More specifically,
the function @code{acc_set_device_num()}.
In the use case presented here, the function @code{acc_set_device_num()}
@ -4456,6 +4456,9 @@ The implementation remark:
@item I/O within OpenMP target regions and OpenACC parallel/kernels is supported
using the C library @code{printf} functions and the Fortran
@code{print}/@code{write} statements.
@item OpenMP code that has a requires directive with @code{unified_address},
@code{unified_shared_memory} or @code{reverse_offload} will remove
any GCN device from the list of available devices (``host fallback'').
@end itemize
@ -4496,7 +4499,7 @@ which caches the JIT in the user's directory (see CUDA documentation; can be
tuned by the environment variables @code{CUDA_CACHE_@{DISABLE,MAXSIZE,PATH@}}.
Note: While PTX ISA is generic, the @code{-mptx=} and @code{-march=} commandline
options still affect the used PTX ISA code and, thus, the requirments on
options still affect the used PTX ISA code and, thus, the requirements on
CUDA version and hardware.
The implementation remark:
@ -4507,6 +4510,15 @@ The implementation remark:
@item Compilation OpenMP code that contains @code{requires reverse_offload}
requires at least @code{-march=sm_35}, compiling for @code{-march=sm_30}
is not supported.
@item For code containing reverse offload (i.e. @code{target} regions with
@code{device(ancestor:1)}), there is a slight performance penalty
for @emph{all} target regions, consisting mostly of shutdown delay
Per device, reverse offload regions are processed serially such that
the next reverse offload region is only executed after the previous
one returned.
@item OpenMP code that has a requires directive with @code{unified_address}
or @code{unified_shared_memory} will remove any nvptx device from the
list of available devices (``host fallback'').
@end itemize