[LTO] Fix -save-temps with LTO and unnamed globals.

[efriedma]

Summary

If all LLVM passes are disabled, we can't emit a summary because there could be unnamed globals in the IR.

[tejohnson]

Thanks. Can you fix the same code in EmitAssemblyWithNewPassManager?

[efriedma]

Fix new pass manager.

[tejohnson]

LGTM

lib/CodeGen/BackendUtil.cpp

void EmitAssemblyHelper::EmitAssembly(BackendAction Action,
 
   std::unique_ptr<llvm::ToolOutputFile> ThinLinkOS, DwoOS;
 
   switch (Action) {
   case Backend_EmitNothing:
     break;
 
   case Backend_EmitBC:
-    if (CodeGenOpts.PrepareForThinLTO) {
+    if (CodeGenOpts.PrepareForThinLTO && !CodeGenOpts.DisableLLVMPasses) {
       if (!CodeGenOpts.ThinLinkBitcodeFile.empty()) {
         ThinLinkOS = openOutputFile(CodeGenOpts.ThinLinkBitcodeFile);
         if (!ThinLinkOS)
           return;
       }
       PerModulePasses.add(createWriteThinLTOBitcodePass(
           *OS, ThinLinkOS ? &ThinLinkOS->os() : nullptr));
     } else {
       // Emit a module summary by default for Regular LTO except for ld64
       // targets
       bool EmitLTOSummary =
           (CodeGenOpts.PrepareForLTO &&
+           !CodeGenOpts.DisableLLVMPasses &&
            llvm::Triple(TheModule->getTargetTriple()).getVendor() !=
                llvm::Triple::Apple);
       if (EmitLTOSummary && !TheModule->getModuleFlag("ThinLTO"))
         TheModule->addModuleFlag(Module::Error, "ThinLTO", uint32_t(0));
 
       PerModulePasses.add(
           createBitcodeWriterPass(*OS, CodeGenOpts.EmitLLVMUseLists,
                                   EmitLTOSummary));

test/CodeGen/summary-index-unnamed-global.ll

+; RUN: %clang_cc1 -flto -triple x86_64-pc-linux-gnu -emit-llvm-bc -disable-llvm-passes -x ir < %s -o - | llvm-bcanalyzer -dump | FileCheck %s
+; RUN: %clang_cc1 -flto=thin -triple x86_64-pc-linux-gnu -emit-llvm-bc -disable-llvm-passes -x ir < %s -o - | llvm-bcanalyzer -dump | FileCheck %s
+
+; CHECK-NOT:GLOBALVAL_SUMMARY_BLOCK
+
+; Make sure this doesn't crash, and we don't try to emit a module summary.
+; (The command is roughly emulating what -save-temps would do.)
+@0 = global i32 0