This fixes a bot failure in the LLDB testsuite.

This removes an assertion that no longer serves its purpose and
relaxes the IRBuilder checks for debug info when generating code
inside the debugger.

When LLDB is JIT-compiling expressions, it will not generate a
SWIFT_ENTRY_POINT_FUNCTION (there will be one per expression)
but it will still generate the equivalent of top level code.

rdar://problem/26955467

Author: adrian-prantl

lib/IRGen/GenDecl.cpp

@@ -539,7 +539,8 @@ void IRGenModule::emitRuntimeRegistration() {
 
   // If we're debugging, we probably don't have a main. Find a
   // function marked with the LLDBDebuggerFunction attribute instead.
-  if (!EntryPoint && Context.LangOpts.DebuggerSupport) {
+  if (Context.LangOpts.DebuggerSupport) {
+    assert(!EntryPoint && "unexpected main");
     for (SILFunction &SF : getSILModule()) {
       if (SF.hasLocation()) {
         if (Decl* D = SF.getLocation().getAsASTNode<Decl>()) {
@@ -573,15 +574,16 @@ void IRGenModule::emitRuntimeRegistration() {
   {
     llvm::BasicBlock *EntryBB = &EntryFunction->getEntryBlock();
     llvm::BasicBlock::iterator IP = EntryBB->getFirstInsertionPt();
-    IRBuilder Builder(getLLVMContext(), DebugInfo);
+    IRBuilder Builder(getLLVMContext(),
+                      DebugInfo && !Context.LangOpts.DebuggerSupport);
     Builder.llvm::IRBuilderBase::SetInsertPoint(EntryBB, IP);
-    if (DebugInfo)
+    if (DebugInfo && !Context.LangOpts.DebuggerSupport)
       DebugInfo->setEntryPointLoc(Builder);
     Builder.CreateCall(RegistrationFunction, {});
   }
 
   IRGenFunction RegIGF(*this, RegistrationFunction);
-  if (DebugInfo)
+  if (DebugInfo && !Context.LangOpts.DebuggerSupport)
     DebugInfo->emitArtificialFunction(RegIGF, RegistrationFunction);
 
   // Register ObjC protocols, classes, and extensions we added.

lib/IRGen/IRGenDebugInfo.cpp

@@ -490,9 +490,6 @@ static CanSILFunctionType getFunctionType(SILType SILTy) {
 llvm::DIScope *IRGenDebugInfo::getEntryPointFn() {
   // Lazily create EntryPointFn.
   if (!EntryPointFn) {
-    auto main = IGM.getSILModule().lookUpFunction(SWIFT_ENTRY_POINT_FUNCTION);
-    assert(main && "emitting TopLevelCodeDecl in module without "
-           SWIFT_ENTRY_POINT_FUNCTION "?");
     EntryPointFn = DBuilder.createReplaceableCompositeType(
       llvm::dwarf::DW_TAG_subroutine_type, SWIFT_ENTRY_POINT_FUNCTION,
         MainFile, MainFile, 0);

lib/IRGen/IRGenFunction.cpp

@@ -31,13 +31,12 @@
 using namespace swift;
 using namespace irgen;
 
-IRGenFunction::IRGenFunction(IRGenModule &IGM,
-                             llvm::Function *Fn,
+IRGenFunction::IRGenFunction(IRGenModule &IGM, llvm::Function *Fn,
                              const SILDebugScope *DbgScope,
                              Optional<SILLocation> DbgLoc)
-  : IGM(IGM), Builder(IGM.getLLVMContext(), IGM.DebugInfo),
-    CurFn(Fn), DbgScope(DbgScope)
-  {
+    : IGM(IGM), Builder(IGM.getLLVMContext(),
+                        IGM.DebugInfo && !IGM.Context.LangOpts.DebuggerSupport),
+      CurFn(Fn), DbgScope(DbgScope) {
 
   // Make sure the instructions in this function are attached its debug scope.
   if (IGM.DebugInfo) {