[OpenCL] __cpp_threadsafe_static_init is by default undefined in OpenCL mode

[Topotuna]

Summary

Definition of __cpp_threadsafe_static_init macro is controlled by
language option Opts.ThreadsafeStatics. This patch sets language
option to false by default in OpenCL mode, resulting in macro
__cpp_threadsafe_static_init being undefined. Default value can be
overriden using command line option -fthreadsafe-statics.

Change is supposed to address portability because not all OpenCL
vendors support thread safe implementation of static initialization.

Fixes llvm.org/PR48012

[Anastasia]

clang/lib/Driver/ToolChains/Clang.cpp

6195–6196

I think this will work fine apart from if someone creates .cpp file but passes -cl-std=clc++. But it is not the conventional flow so I think we should not worry about it for now.

clang/test/Driver/threadsafe-statics.clcpp

3

Worth adding one more RUN line with -fthreadsafe-statics passed.

[Topotuna]

clang/test/Driver/threadsafe-statics.clcpp

3

Such RUN line is present on line 8. Should I move it up so that all RUN lines are close to one another?

[Anastasia]

LGTM! Thanks!

clang/lib/Driver/ToolChains/Clang.cpp

if (Args.hasFlag(options::OPT_fdeclspec, options::OPT_fno_declspec,
     CmdArgs.push_back("-fdeclspec");
   else if (Args.hasArg(options::OPT_fno_declspec))
     CmdArgs.push_back("-fno-declspec"); // Explicitly disabling __declspec.
 
   // -fthreadsafe-static is default, except for MSVC compatibility versions less
   // than 19.
   if (!Args.hasFlag(options::OPT_fthreadsafe_statics,
                     options::OPT_fno_threadsafe_statics,
-                    !IsWindowsMSVC || IsMSVC2015Compatible))
+                    !types::isOpenCL(InputType) &&
+                        (!IsWindowsMSVC || IsMSVC2015Compatible)))
     CmdArgs.push_back("-fno-threadsafe-statics");
 
   // -fno-delayed-template-parsing is default, except when targeting MSVC.
   // Many old Windows SDK versions require this to parse.
   // FIXME: MSVC introduced /Zc:twoPhase- to disable this behavior in their
   // compiler. We should be able to disable this by default at some point.
   if (Args.hasFlag(options::OPT_fdelayed_template_parsing,
                    options::OPT_fno_delayed_template_parsing, IsWindowsMSVC))

clang/test/Driver/threadsafe-statics.clcpp

+// RUN: %clang -### -c -DNO_THREADSAFE_STATICS %s 2>&1 | FileCheck --check-prefix=CHECK-NO-THREADSAFE-STATICS %s
+// RUN: %clang -### -fno-threadsafe-statics -DNO_THREADSAFE_STATICS -c %s 2>&1 | FileCheck --check-prefix=CHECK-NO-THREADSAFE-STATICS %s
+
+// CHECK-NO-THREADSAFE-STATICS: "-cc1"
+// CHECK-NO-THREADSAFE-STATICS: "-fno-threadsafe-statics"
+// CHECK-NO-THREADSAFE-STATICS-NOT: "-fthreadsafe-statics"
+
+// RUN: %clang -### -fthreadsafe-statics -DTHREADSAFE_STATICS -c %s 2>&1 | FileCheck --check-prefix=CHECK-THREADSAFE-STATICS %s
+
+// CHECK-THREADSAFE-STATICS: "-cc1"
+// CHECK-THREADSAFE-STATICS-NOT: "-fno-threadsafe-statics"