[clang] [llvm] [clang][llvm][fatlto] Avoid cloning modules in FatLTO (PR #72180)

[Teresa Johnson via cfe-commits]

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@@ -810,7 +810,7 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
   // Only enable CGProfilePass when using integrated assembler, since
   // non-integrated assemblers don't recognize .cgprofile section.
   PTO.CallGraphProfile = !CodeGenOpts.DisableIntegratedAS;
-  PTO.UnifiedLTO = CodeGenOpts.UnifiedLTO;
+  PTO.UnifiedLTO = CodeGenOpts.UnifiedLTO || CodeGenOpts.FatLTO;
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teresajohnson wrote:

Actually, I believe the cc1 parsing is handled by ParseCodeGenArgs in clang/lib/Frontend/CompilerInvocation.cpp. You can potentially add something in there to ensure UnifiedLTO is set with FatLTO? Or give your error there that UnifiedLTO must be specified with Fat LTO.

https://github.com/llvm/llvm-project/pull/72180