[Openmp-commits] [PATCH] D121007: [Libomptarget] Work around bug in initialization of libomptarget

[Joseph Huber via Phabricator via Openmp-commits]

jhuber6 created this revision.
jhuber6 added reviewers: jdoerfert, tianshilei1992, JonChesterfield.
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jhuber6 requested review of this revision.
Herald added subscribers: openmp-commits, sstefan1.
Herald added a project: OpenMP.

Libomptarget uses some shared variables to track certain internal stated
in the runtime. This causes problems when we have code that contains no
OpenMP kernels. These varaibles are normally initialized upon kernel
entry, but if there are no kernels we will see no initialization.
Currently we load the runtime into each source file when not running in
LTO mode, so these variables will be erroenously considered undefined or
dead and removed, causing miscompiles. This patch temporarily works
around the most obvious case, but others still exhibit this problem. We
will need to fix this more soundly later.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D121007

Files:
  openmp/libomptarget/DeviceRTL/src/Mapping.cpp


Index: openmp/libomptarget/DeviceRTL/src/Mapping.cpp
===================================================================
--- openmp/libomptarget/DeviceRTL/src/Mapping.cpp
+++ openmp/libomptarget/DeviceRTL/src/Mapping.cpp
@@ -258,7 +258,10 @@
 /// Execution mode
 ///
 ///{
-static int SHARED(IsSPMDMode);
+
+// TODO: This is a workaround for initialization coming from kernels outside of
+//       the TU. We will need to solve this more correctly in the future.
+int __attribute__((used, retain, weak)) SHARED(IsSPMDMode);
 
 void mapping::init(bool IsSPMD) {
   if (mapping::isInitialThreadInLevel0(IsSPMD))


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