Removing the changes from ThinLTO

Author: anchuraj

flang/lib/Frontend/FrontendActions.cpp

@@ -1024,9 +1024,6 @@ void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
   bool emitSummary = (opts.PrepareForThinLTO || opts.PrepareForFullLTO) &&
                      (triple.getVendor() != llvm::Triple::Apple);
 
-  if (emitSummary && !opts.PrepareForThinLTO)
-    llvmModule->addModuleFlag(llvm::Module::Error, "ThinLTO", uint32_t(0));
-
   if (opts.PrepareForFatLTO)
     mpm = pb.buildFatLTODefaultPipeline(level, opts.PrepareForThinLTO,
                                         emitSummary);
@@ -1037,12 +1034,29 @@ void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
   else
     mpm = pb.buildPerModuleDefaultPipeline(level);
 
-  if (action == BackendActionTy::Backend_EmitBC)
-    mpm.addPass(llvm::BitcodeWriterPass(
-        os, /*ShouldPreserveUseListOrder=*/false, emitSummary));
-  else if (action == BackendActionTy::Backend_EmitLL)
-    mpm.addPass(llvm::PrintModulePass(
-        os, /*Banner=*/"", /*ShouldPreserveUseListOrder=*/false, emitSummary));
+  if (action == BackendActionTy::Backend_EmitBC ||
+      action == BackendActionTy::Backend_EmitLL || opts.PrepareForFatLTO) {
+    if (opts.PrepareForThinLTO) {
+      // TODO: ThinLTO module summary support is yet to be enabled.
+      if (action == BackendActionTy::Backend_EmitBC)
+        mpm.addPass(llvm::BitcodeWriterPass(os));
+      else if (action == BackendActionTy::Backend_EmitLL)
+        mpm.addPass(llvm::PrintModulePass(os));
+    } else {
+      if (emitSummary) {
+        if (!llvmModule->getModuleFlag("ThinLTO"))
+          llvmModule->addModuleFlag(llvm::Module::Error, "ThinLTO",
+                                    uint32_t(0));
+      }
+      if (action == BackendActionTy::Backend_EmitBC)
+        mpm.addPass(llvm::BitcodeWriterPass(
+            os, /*ShouldPreserveUseListOrder=*/false, emitSummary));
+      else if (action == BackendActionTy::Backend_EmitLL)
+        mpm.addPass(llvm::PrintModulePass(os, /*Banner=*/"",
+                                          /*ShouldPreserveUseListOrder=*/false,
+                                          emitSummary));
+    }
+  }
 
   // FIXME: This should eventually be replaced by a first-class driver option.
   // This should be done for both flang and clang simultaneously.

flang/test/Driver/lto-bc.f90

@@ -12,13 +12,7 @@
 ! CHECK-NOT: ^{{.*}} = blockcount:
 
 ! RUN: %flang -flto=thin %s -c -o - | llvm-dis -o - | FileCheck %s --check-prefix=THIN
-! THIN: define void @_QQmain()
-! THIN-NEXT:  ret void
-! THIN-NEXT: }
 ! THIN-NOT: !{{.*}} = !{i32 1, !"ThinLTO", i32 0}
-! THIN: ^{{.*}} = module:
-! THIN: ^{{.*}} = gv: (name:
-! THIN: ^{{.*}} = blockcount:
 
 ! RUN: %flang -flto %s -c -o - | llvm-dis -o - | FileCheck %s --check-prefix=FULL
 ! FULL: define void @_QQmain()