[Offload] Check for initialization

All entry points (except olInit) now check that offload has been
initialized. If not, a new `OL_ERRC_UNINITIALIZED` error is returned.

Author: RossBrunton

offload/liboffload/API/Common.td

@@ -106,6 +106,7 @@ def ErrorCode : Enum {
     Etor<"ASSEMBLE_FAILURE", "assembler failure while processing binary image">,
     Etor<"LINK_FAILURE", "linker failure while processing binary image">,
     Etor<"BACKEND_FAILURE", "the plugin backend is in an invalid or unsupported state">,
+    Etor<"UNINITIALIZED", "not initialized">,
 
     // Handle related errors - only makes sense for liboffload
     Etor<"INVALID_NULL_HANDLE", "a handle argument is null when it should not be">,

offload/liboffload/include/OffloadImpl.hpp

@@ -26,6 +26,7 @@ namespace llvm {
 namespace offload {
 bool isTracingEnabled();
 bool isValidationEnabled();
+bool isOffloadInited();
 } // namespace offload
 } // namespace llvm
 

offload/liboffload/src/OffloadImpl.cpp

@@ -120,9 +120,10 @@ struct OffloadContext {
 
 // If the context is uninited, then we assume tracing is disabled
 bool isTracingEnabled() {
-  return OffloadContextVal && OffloadContext::get().TracingEnabled;
+  return isOffloadInited() && OffloadContext::get().TracingEnabled;
 }
 bool isValidationEnabled() { return OffloadContext::get().ValidationEnabled; }
+bool isOffloadInited() { return OffloadContextVal != nullptr; }
 
 template <typename HandleT> Error olDestroy(HandleT Handle) {
   delete Handle;

offload/tools/offload-tblgen/EntryPointGen.cpp

@@ -82,6 +82,10 @@ static void EmitEntryPointFunc(const FunctionRec &F, raw_ostream &OS) {
   }
   OS << ") {\n";
 
+  // Check offload is inited
+  if (F.getName() != "olInit")
+    OS << "if (!llvm::offload::isOffloadInited()) return &UninitError;";
+
   // Emit pre-call prints
   OS << TAB_1 "if (llvm::offload::isTracingEnabled()) {\n";
   OS << formatv(TAB_2 "llvm::errs() << \"---> {0}\";\n", F.getName());
@@ -143,6 +147,14 @@ static void EmitCodeLocWrapper(const FunctionRec &F, raw_ostream &OS) {
 
 void EmitOffloadEntryPoints(const RecordKeeper &Records, raw_ostream &OS) {
   OS << GenericHeader;
+
+  constexpr const char *UninitMessage =
+      "liboffload has not been initialized - please call olInit before using "
+      "this API";
+  OS << formatv("static {0}_error_struct_t UninitError = "
+                "{{{1}_ERRC_UNINITIALIZED, \"{2}\"};",
+                PrefixLower, PrefixUpper, UninitMessage);
+
   for (auto *R : Records.getAllDerivedDefinitions("Function")) {
     EmitValidationFunc(FunctionRec{R}, OS);
     EmitEntryPointFunc(FunctionRec{R}, OS);