[OpenMP] Use weak attribute in interface only for static library

This is to address the issue reported at:
https://bugs.llvm.org/show_bug.cgi?id=46863

Since weak is meaningless for a shared library interface function, this patch
disables the attribute, when the OpenMP library is built as shared library.

ompt_start_tool is not an interface function, but a internally called function
possibly implemented by an OMPT tool.
This function needs to be weak if possible to allow overwriting ompt_start_tool
with a function implementation built into the application.

Differential Revision: https://reviews.llvm.org/D84871

openmp/runtime/src/kmp_ftn_entry.h

@@ -939,7 +939,7 @@ void FTN_STDCALL KMP_EXPAND_NAME(FTN_SET_DEFAULT_DEVICE)(int KMP_DEREF arg) {
 
 // Get number of NON-HOST devices.
 // libomptarget, if loaded, provides this function in api.cpp.
-int FTN_STDCALL KMP_EXPAND_NAME(FTN_GET_NUM_DEVICES)(void) KMP_WEAK_ATTRIBUTE;
+int FTN_STDCALL KMP_EXPAND_NAME(FTN_GET_NUM_DEVICES)(void) KMP_WEAK_ATTRIBUTE_EXTERNAL;
 int FTN_STDCALL KMP_EXPAND_NAME(FTN_GET_NUM_DEVICES)(void) {
 #if KMP_MIC || KMP_OS_DARWIN || KMP_OS_WINDOWS || defined(KMP_STUB)
   return 0;
@@ -957,13 +957,13 @@ int FTN_STDCALL KMP_EXPAND_NAME(FTN_GET_NUM_DEVICES)(void) {
 
 // This function always returns true when called on host device.
 // Compiler/libomptarget should handle when it is called inside target region.
-int FTN_STDCALL KMP_EXPAND_NAME(FTN_IS_INITIAL_DEVICE)(void) KMP_WEAK_ATTRIBUTE;
+int FTN_STDCALL KMP_EXPAND_NAME(FTN_IS_INITIAL_DEVICE)(void) KMP_WEAK_ATTRIBUTE_EXTERNAL;
 int FTN_STDCALL KMP_EXPAND_NAME(FTN_IS_INITIAL_DEVICE)(void) {
   return 1; // This is the host
 }
 
 // libomptarget, if loaded, provides this function
-int FTN_STDCALL FTN_GET_INITIAL_DEVICE(void) KMP_WEAK_ATTRIBUTE;
+int FTN_STDCALL FTN_GET_INITIAL_DEVICE(void) KMP_WEAK_ATTRIBUTE_EXTERNAL;
 int FTN_STDCALL FTN_GET_INITIAL_DEVICE(void) {
 #if KMP_MIC || KMP_OS_DARWIN || KMP_OS_WINDOWS || defined(KMP_STUB)
   return KMP_HOST_DEVICE;
@@ -1318,7 +1318,7 @@ int FTN_STDCALL KMP_EXPAND_NAME(FTN_GET_MAX_TASK_PRIORITY)(void) {
 // This function will be defined in libomptarget. When libomptarget is not
 // loaded, we assume we are on the host and return KMP_HOST_DEVICE.
 // Compiler/libomptarget will handle this if called inside target.
-int FTN_STDCALL FTN_GET_DEVICE_NUM(void) KMP_WEAK_ATTRIBUTE;
+int FTN_STDCALL FTN_GET_DEVICE_NUM(void) KMP_WEAK_ATTRIBUTE_EXTERNAL;
 int FTN_STDCALL FTN_GET_DEVICE_NUM(void) { return KMP_HOST_DEVICE; }
 
 // Compiler will ensure that this is only called from host in sequential region

openmp/runtime/src/kmp_os.h

@@ -338,10 +338,16 @@ extern "C" {
 #define KMP_ALIAS(alias_of) __attribute__((alias(alias_of)))
 #endif
 
+#if KMP_HAVE_WEAK_ATTRIBUTE && !KMP_DYNAMIC_LIB
+#define KMP_WEAK_ATTRIBUTE_EXTERNAL __attribute__((weak))
+#else
+#define KMP_WEAK_ATTRIBUTE_EXTERNAL /* Nothing */
+#endif
+
 #if KMP_HAVE_WEAK_ATTRIBUTE
-#define KMP_WEAK_ATTRIBUTE __attribute__((weak))
+#define KMP_WEAK_ATTRIBUTE_INTERNAL __attribute__((weak))
 #else
-#define KMP_WEAK_ATTRIBUTE /* Nothing */
+#define KMP_WEAK_ATTRIBUTE_INTERNAL /* Nothing */
 #endif
 
 // Define KMP_VERSION_SYMBOL and KMP_EXPAND_NAME

openmp/runtime/src/ompt-specific.cpp

@@ -27,7 +27,7 @@
 #define THREAD_LOCAL __thread
 #endif
 
-#define OMPT_WEAK_ATTRIBUTE KMP_WEAK_ATTRIBUTE
+#define OMPT_WEAK_ATTRIBUTE KMP_WEAK_ATTRIBUTE_INTERNAL
 
 //******************************************************************************
 // macros