[Profiler] Use proper SILDeclRef for top-level code

Use a main entry-point instead of a null
SILDeclRef. Eventually we'll want to unify the
emission here such that we visit all the
TopLevelDecls in one shot (and just use a single
profiler), but for now we can just hand the
SILProfiler the expected SILDeclRef.

Author: hamishknight

lib/SIL/IR/SILFunction.cpp

@@ -334,8 +334,11 @@ void SILFunction::deleteSnapshot(int ID) {
 
 void SILFunction::createProfiler(ASTNode Root, SILDeclRef Ref) {
   assert(!Profiler && "Function already has a profiler");
+  assert(Root && "Cannot profile a null ASTNode");
+  assert(Ref && "Must have non-null SILDeclRef");
+
   Profiler = SILProfiler::create(Module, Root, Ref);
-  if (!Profiler || Ref.isNull())
+  if (!Profiler)
     return;
 
   // If we loaded a profile, set the entry counts for functions and closures

lib/SIL/IR/SILProfiler.cpp

@@ -40,14 +40,6 @@ static bool shouldProfile(ASTNode N, SILDeclRef Constant) {
                << "Skipping ASTNode: invalid start/end locations\n");
     return false;
   }
-  if (!Constant) {
-    // We should only ever have a null SILDeclRef for top-level code, which is
-    // always user-written, and should always be profiled.
-    // FIXME: Once top-level code is unified under a single SILProfiler, this
-    // case can be eliminated.
-    assert(isa<TopLevelCodeDecl>(N.get<Decl *>()));
-    return true;
-  }
 
   // Do not profile AST nodes in unavailable contexts.
   auto *DC = Constant.getInnermostDeclContext();

lib/SILGen/SILGen.cpp

@@ -1946,10 +1946,20 @@ void SILGenModule::visitTopLevelCodeDecl(TopLevelCodeDecl *td) {
   if (!TopLevelSGF->B.hasValidInsertionPoint())
     return;
 
+  // Retrieve the entry point constant we're emitting for.
+  // FIXME: This won't be necessary once we unify emission of the entry point
+  // such that we walk all of the TopLevelCodeDecls in one shot. This will be
+  // needed in order to requestify entry point emission.
+  auto *SF = td->getParentSourceFile();
+  assert(SF && "TopLevelDecl outside of a SourceFile?");
+  auto entryPoint = TopLevelSGF->F.isAsync()
+                      ? SILDeclRef::getAsyncMainFileEntryPoint(SF)
+                      : SILDeclRef::getMainFileEntryPoint(SF);
+
   // A single SILFunction may be used to lower multiple top-level decls. When
   // this happens, fresh profile counters must be assigned to the new decl.
   TopLevelSGF->F.discardProfiler();
-  TopLevelSGF->F.createProfiler(td, SILDeclRef());
+  TopLevelSGF->F.createProfiler(td, entryPoint);
 
   TopLevelSGF->emitProfilerIncrement(td->getBody());