From 9584ea20bbd81f1d56dd095a336f1b676751662c Mon Sep 17 00:00:00 2001
From: Sergey V Maslov <sergey.v.maslov@intel.com>
Date: Wed, 29 Apr 2020 11:44:57 -0700
Subject: [PATCH 1/2] [SYCL] Load PI plugins only once

Signed-off-by: Sergey V Maslov <sergey.v.maslov@intel.com>
---
 sycl/source/detail/pi.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
 mode change 100644 => 100755 sycl/source/detail/pi.cpp

diff --git a/sycl/source/detail/pi.cpp b/sycl/source/detail/pi.cpp
old mode 100644
new mode 100755
index a85590b30e843..ca1c7ceaa3031
--- a/sycl/source/detail/pi.cpp
+++ b/sycl/source/detail/pi.cpp
@@ -197,7 +197,12 @@ bool trace(TraceLevel Level) {
 
 // Initializes all available Plugins.
 vector_class<plugin> initialize() {
-  vector_class<plugin> Plugins;
+  static bool PluginsInitDone = false;
+  static vector_class<plugin> Plugins;
+  if (PluginsInitDone) {
+    return Plugins;
+  }
+
   vector_class<std::pair<std::string, backend>> PluginNames;
   findPlugins(PluginNames);
 
@@ -244,6 +249,7 @@ vector_class<plugin> initialize() {
                 << "Plugin found and successfully loaded: "
                 << PluginNames[I].first << std::endl;
   }
+  PluginsInitDone = true;
 
 #ifdef XPTI_ENABLE_INSTRUMENTATION
   if (!(xptiTraceEnabled() && !XPTIInitDone))

From 5a3df8f826215d1760fcf89f69d5443156385635 Mon Sep 17 00:00:00 2001
From: Sergey V Maslov <sergey.v.maslov@intel.com>
Date: Fri, 5 Jun 2020 00:07:01 -0700
Subject: [PATCH 2/2] [SYCL] Load PI plugins only once. Make pi::initialize
 return const reference to the global vector of plugins, not a temporary copy
 of it.

Change-Id: Ic1373059c9697b0b4d318548b79be7bcb9d4f2a9
Signed-off-by: Sergey V Maslov <sergey.v.maslov@intel.com>
---
 sycl/include/CL/sycl/detail/pi.hpp   | 2 +-
 sycl/source/detail/pi.cpp            | 8 +++++++-
 sycl/source/detail/platform_impl.cpp | 2 +-
 3 files changed, 9 insertions(+), 3 deletions(-)
 mode change 100755 => 100644 sycl/source/detail/pi.cpp

diff --git a/sycl/include/CL/sycl/detail/pi.hpp b/sycl/include/CL/sycl/detail/pi.hpp
index 113255d60beba..ee0a37a515e97 100644
--- a/sycl/include/CL/sycl/detail/pi.hpp
+++ b/sycl/include/CL/sycl/detail/pi.hpp
@@ -135,7 +135,7 @@ template <class To, class From> To cast(From value);
 extern std::shared_ptr<plugin> GlobalPlugin;
 
 // Performs PI one-time initialization.
-vector_class<plugin> initialize();
+const vector_class<plugin> &initialize();
 
 // Utility Functions to get Function Name for a PI Api.
 template <PiApiKind PiApiOffset> struct PiFuncInfo {};
diff --git a/sycl/source/detail/pi.cpp b/sycl/source/detail/pi.cpp
old mode 100755
new mode 100644
index 13fd2c3bdb3e0..17fc470f6407b
--- a/sycl/source/detail/pi.cpp
+++ b/sycl/source/detail/pi.cpp
@@ -255,7 +255,13 @@ bool trace(TraceLevel Level) {
 }
 
 // Initializes all available Plugins.
-vector_class<plugin> initialize() {
+// The returned reference lifetime is through the end of the process.
+//
+// TODO: make sure that the global Plugins is destroyed last, at least
+// after other tear-down relying on plugins (like destructors of global
+// buffers) is completed.
+//
+const vector_class<plugin> &initialize() {
   static bool PluginsInitDone = false;
   static vector_class<plugin> Plugins;
   if (PluginsInitDone) {
diff --git a/sycl/source/detail/platform_impl.cpp b/sycl/source/detail/platform_impl.cpp
index 6d10960664656..daabe5722f754 100644
--- a/sycl/source/detail/platform_impl.cpp
+++ b/sycl/source/detail/platform_impl.cpp
@@ -49,7 +49,7 @@ static bool IsBannedPlatform(platform Platform) {
 
 vector_class<platform> platform_impl::get_platforms() {
   vector_class<platform> Platforms;
-  vector_class<plugin> Plugins = RT::initialize();
+  const vector_class<plugin> &Plugins = RT::initialize();
 
   info::device_type ForcedType = detail::get_forced_type();
   for (unsigned int i = 0; i < Plugins.size(); i++) {