[offload] defer "---> olInit" trace message (llvm#167893)

Tracing requires liboffload to be initialized, so calling
isTracingEnabled() before olInit always returns false. This caused the
first trace log to look like:
```
-> OL_SUCCESS
```
instead of:
```
---> olInit() -> OL_SUCCESS
```
This patch moves the pre-call trace print for olInit so it is emitted
only after initialization.

It would be possible to add extra logic to detect whether liboffload is
already initialized and only postpone the first pre-call print, but this
would add unnecessary complexity, especially since this is tablegen
code. The difference would matter only in the unlikely case of a crash
during a second olInit call.

---------

Co-authored-by: Joseph Huber <huberjn@outlook.com>

Author: lplewa

offload/tools/offload-tblgen/EntryPointGen.cpp

@@ -83,13 +83,15 @@ static void EmitEntryPointFunc(const FunctionRec &F, raw_ostream &OS) {
   OS << ") {\n";
 
   // Check offload is initialized
-  if (F.getName() != "olInit")
+  if (F.getName() != "olInit") {
     OS << "if (!llvm::offload::isOffloadInitialized()) return &UninitError;";
 
-  // Emit pre-call prints
-  OS << TAB_1 "if (llvm::offload::isTracingEnabled()) {\n";
-  OS << formatv(TAB_2 "llvm::errs() << \"---> {0}\";\n", F.getName());
-  OS << TAB_1 "}\n\n";
+    // Emit pre-call prints
+    // Postpone pre-calls for olInit as tracing requires liboffload to be initialized
+    OS << TAB_1 "if (llvm::offload::isTracingEnabled()) {\n";
+    OS << formatv(TAB_2 "llvm::errs() << \"---> {0}\";\n", F.getName());
+    OS << TAB_1 "}\n\n";
+  }
 
   // Perform actual function call to the validation wrapper
   ParamNameList = ParamNameList.substr(0, ParamNameList.size() - 2);
@@ -99,6 +101,10 @@ static void EmitEntryPointFunc(const FunctionRec &F, raw_ostream &OS) {
 
   // Emit post-call prints
   OS << TAB_1 "if (llvm::offload::isTracingEnabled()) {\n";
+  // postponed pre-call print for olInit
+  if (F.getName() == "olInit")
+    OS << formatv(TAB_2 "llvm::errs() << \"---> {0}\";\n", F.getName());
+
   if (F.getParams().size() > 0) {
     OS << formatv(TAB_2 "{0} Params = {{", F.getParamStructName());
     for (const auto &Param : F.getParams()) {