[PATCH] D41267: [LTO] Write LTO output for empty RegularLTO.ModsWithSummaries

[Peter Collingbourne via Phabricator via llvm-commits]

pcc added a comment.

I think this patch can be simplified with my suggestions below. Let me know if it works.



================
Comment at: llvm/include/llvm/LTO/LTO.h:283-284
     bool HasModule = false;
     std::unique_ptr<Module> CombinedModule;
     std::unique_ptr<IRMover> Mover;
 
----------------
Change these to:
```
Module CombinedModule;
IRMover Mover;
```
and have them be initialized by the `RegularLTOState` constructor in the same way as `LTO::linkRegularLTO` is doing right now.


================
Comment at: llvm/include/llvm/LTO/LTO.h:295
     std::vector<AddedModule> ModsWithSummaries;
+    std::string EmptyModuleTargetTriple;
   } RegularLTO;
----------------
Remove this field.


================
Comment at: llvm/lib/LTO/LTO.cpp:472
 
+  if (RegularLTO.EmptyModuleTargetTriple.empty())
+    RegularLTO.EmptyModuleTargetTriple = Input->getTargetTriple();
----------------
Make this code use `RegularLTO.CombinedModule.{g,s}etTargetTriple()` instead.


================
Comment at: llvm/lib/LTO/LTO.cpp:662-667
   if (!RegularLTO.CombinedModule) {
     RegularLTO.CombinedModule =
         llvm::make_unique<Module>("ld-temp.o", RegularLTO.Ctx);
     RegularLTO.Mover = llvm::make_unique<IRMover>(*RegularLTO.CombinedModule);
   }
 
----------------
Remove this code.


================
Comment at: llvm/lib/LTO/LTO.cpp:744
+  // Reserve one for empty module.
+  return 1 + RegularLTO.ParallelCodeGenParallelismLevel +
+         ThinLTO.ModuleMap.size();
----------------
I don't think you need to add 1 here. With my suggestions, module 0 will be the empty module.


================
Comment at: llvm/lib/LTO/LTO.cpp:768
   // Invoke regular LTO if there was a regular LTO module to start with.
-  if (HasRegularLTO)
+  if (HasRegularLTO) {
     if (auto E = runRegularLTO(AddStream))
----------------
Remove this line.


================
Comment at: llvm/lib/LTO/LTO.cpp:771-782
+  } else {
+    // Create empty output to have consistency and avoid workarounds workaround
+    // on build system side for missing build rule output.
+    std::unique_ptr<Module> Mod =
+        make_unique<Module>("empty.o", RegularLTO.Ctx);
+    Mod->setTargetTriple(RegularLTO.EmptyModuleTargetTriple);
+    ModuleSummaryIndex EmptyIndex;
----------------
Remove all of this.


https://reviews.llvm.org/D41267