[IRGen] Remove unnecessary IRGenOptions flag HasUnderlyingModule.

The test that it's guarding is cheap enough to do all the time, and we
don't have any interesting configurations where it's not set any more.

Swift SVN r29442

Author: jrose-apple

include/swift/AST/IRGenOptions.h

@@ -97,9 +97,6 @@ class IRGenOptions {
 
   /// Disable frame pointer elimination?
   unsigned DisableFPElim : 1;
-
-  /// Whether or not this is the Swift half of a mixed-source framework.
-  unsigned HasUnderlyingModule : 1;
 
   /// Special codegen for playgrounds.
   unsigned Playground : 1;
@@ -124,8 +121,8 @@ class IRGenOptions {
                    Optimize(false), DebugInfoKind(IRGenDebugInfoKind::None),
                    UseJIT(false), DisableLLVMOptzns(false),
                    DisableLLVMARCOpts(false), DisableLLVMSLPVectorizer(false),
-                   DisableFPElim(true), HasUnderlyingModule(false),
-                   Playground(false), GenerateProfile(false),
+                   DisableFPElim(true), Playground(false),
+                   GenerateProfile(false),
                    EmbedMode(IRGenEmbedMode::None) {}
 
   /// Gets the name of the specified output filename.

lib/Frontend/CompilerInvocation.cpp

@@ -1018,8 +1018,6 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
   if (Args.hasArg(OPT_disable_llvm_verify))
     Opts.Verify = false;
 
-  Opts.HasUnderlyingModule |= Args.hasArg(OPT_import_underlying_module);
-
   if (Args.hasArg(OPT_autolink_force_load))
     Opts.ForceLoadSymbolName = Args.getLastArgValue(OPT_module_link_name);
 

lib/IRGen/GenDecl.cpp

@@ -436,8 +436,7 @@ void IRGenModule::emitSourceFile(SourceFile &SF, unsigned StartElem) {
 
   SF.forAllVisibleModules([&](swift::Module::ImportedModule import) {
     swift::Module *next = import.second;
-    if (Opts.HasUnderlyingModule &&
-        next->getName() == SF.getParentModule()->getName())
+    if (next->getName() == SF.getParentModule()->getName())
       return;
 
     next->collectLinkLibraries([this](LinkLibrary linkLib) {

lib/IRGen/IRGen.cpp

@@ -432,7 +432,7 @@ static std::unique_ptr<llvm::Module> performIRGeneration(IRGenOptions &Opts,
       continue;
     prev = next;
 
-    if (Opts.HasUnderlyingModule && next->getName() == M->getName())
+    if (next->getName() == M->getName())
       continue;
 
     next->collectLinkLibraries([&](LinkLibrary linkLib) {
@@ -566,7 +566,7 @@ static void performParallelIRGeneration(IRGenOptions &Opts,
       continue;
     prev = next;
 
-    if (Opts.HasUnderlyingModule && next->getName() == M->getName())
+    if (next->getName() == M->getName())
       continue;
 
     next->collectLinkLibraries([&](LinkLibrary linkLib) {