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[OpenMP][FIX] Do not signal SPMD-mode but then keep generic-mode

Authored by jdoerfert on Oct 31 2021, 12:52 PM.



If we assume SPMD-mode during the fixpoint iteration we have to execute
the kernel in SPMD-mode. If we change our mind during manifest there is
the chance of a mismatch between the simplification, e.g., of
__kmpc_is_spmd_exec_mode calls, and the execution mode. This problem
was introduced in D109438.

This patch is compromise to resolve the problem purely in OpenMP-opt
while trying to keep the benefits of D109438 around. This might not
always work, see get_hardware_num_threads_in_block_fold but it often
does. At the same time we do keep value specialization and execution
mode in sync.

Proper solutions to this problem should be considered. I believe a new
execution mode is the easiest way forward (Singleton-SPMD).
Alternatively, SPMD-mode execution can be used with a way to provide a
new thread_limit (here 1) to the runtime. This is more general and could
be useful if we see num_threads clauses or workshared loops with small
trip counts in the kernel. In either proposal we need to disable the
guarding for the kernel (which was the motivation for D109438).

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Event Timeline

jdoerfert created this revision.Oct 31 2021, 12:52 PM
jdoerfert requested review of this revision.Oct 31 2021, 12:52 PM
Herald added a reviewer: baziotis. · View Herald Transcript
Herald added a project: Restricted Project. · View Herald Transcript
jhuber6 accepted this revision.Nov 1 2021, 6:55 AM


This revision is now accepted and ready to land.Nov 1 2021, 6:55 AM
This revision was landed with ongoing or failed builds.Nov 2 2021, 9:23 PM
This revision was automatically updated to reflect the committed changes.