[ThinLTO] Append original object file name to ThinLTO generated object file's name, so that it can be recorded in link map file.

[xushuangqing]

Summary

Problem

When I use ThinLTO, ThinLTOCodeGenerator will generate object file whose filename looks like this:

0.x86_64.thinlto.o
1.x86_64.thinlto.o
2.x86_64.thinlto.o
3.x86_64.thinlto.o

So when I use -map option during linking, the generated link map file will contain these object files. It looks like:

# Path: ...
# Arch: x86_64
# Object files:
[  0] linker synthesized
...
[ 10] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/0.x86_64.thinlto.o
[ 11] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/1.x86_64.thinlto.o
[ 12] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/2.x86_64.thinlto.o
[ 13] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/3.x86_64.thinlto.o
[ 14] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/4.x86_64.thinlto.o

# Sections:
# Address Size      Segment Section
...

# Symbols:
# Address Size      File  Name
...

# Dead Stripped Symbols:
#         Size      File  Name
...

If I want to figure out each source file's size in the binary file, the 0.x86_64.thinlto.o confuses me. It contains few information about the original source file.

Optimize

As filenames like 0.x86_64.thinlto.o are joint in ThinLTOCodeGenerator::writeGeneratedObject, we can append the original object file name to it.

So the file name would looks like:

[ 10] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/0.x86_64.ViewController.o0.thinlto.o
[ 11] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/1.x86_64.AppDelegate.o1.thinlto.o
[ 12] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/2.x86_64.main.o2.thinlto.o
[ 13] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/3.x86_64.SceneDelegate.o3.thinlto.o
[ 14] /Users/xushuangqing/Library/Developer/Xcode/DerivedData/XSQLTODemo-flxqbdftarzrkoeyxgvupfvnvbue/Build/Intermediates.noindex/XSQLTODemo.build/Release-iphonesimulator/XSQLTODemo.build/Objects-normal/x86_64/XSQLTODemo_lto.o/4.x86_64.libXSQStaticLib.a(XSQObject.o)4.thinlto.o

When we analyze the link map, we can figure out each source file's size in the binary file.

[xushuangqing]

Update unit test case.

[steven_wu]

The best solution might still be the linker to map the intermediate file to the original object file since the added file name here is still another level of indirection you need to figure out. @davide for his opinion.

Can you add a testcase?

[davide]

In D112124#3080812, @steven_wu wrote:

The best solution might still be the linker to map the intermediate file to the original object file since the added file name here is still another level of indirection you need to figure out. @davide for his opinion.

That sounds like a reasonable solution to me.

Can you add a testcase?

[xushuangqing]

In D112124#3080812, @steven_wu wrote:

The best solution might still be the linker to map the intermediate file to the original object file since the added file name here is still another level of indirection you need to figure out. @davide for his opinion.

Thank you for your suggestion. It sounds reasonable.
I should think about the solution again.

llvm/include/llvm/LTO/legacy/ThinLTOCodeGenerator.h

    * SavedObjectsDirectoryPath.
    */
   std::string writeGeneratedObject(int count, StringRef CacheEntryPath,
-                                   const MemoryBuffer &OutputBuffer);
+                                   const MemoryBuffer &OutputBuffer,
+                                   StringRef objectFileName = "");
   /**@}*/
 
 private:

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

 /// Returns the path to the generated file in SavedObjectsDirectoryPath.
 std::string
 ThinLTOCodeGenerator::writeGeneratedObject(int count, StringRef CacheEntryPath,
-                                           const MemoryBuffer &OutputBuffer) {
+                                           const MemoryBuffer &OutputBuffer,
+                                           StringRef objectFileName) {
   auto ArchName = TMBuilder.TheTriple.getArchName();
   SmallString<128> OutputPath(SavedObjectsDirectoryPath);
-  llvm::sys::path::append(OutputPath,
-                          Twine(count) + "." + ArchName + ".thinlto.o");
+  if (objectFileName.empty())
+    llvm::sys::path::append(OutputPath,
+                            Twine(count) + "." + ArchName + ".thinlto.o");
+  else
+    llvm::sys::path::append(OutputPath, Twine(count) + "." + ArchName + "." +
+                                            objectFileName + ".thinlto.o");
   OutputPath.c_str(); // Ensure the string is null terminated.
   if (sys::fs::exists(OutputPath))
     sys::fs::remove(OutputPath);

       auto &Mod = Modules[IndexCount];
       Pool.async([&](int count) {
         auto ModuleIdentifier = Mod->getName();
+
+        StringRef moduleIdentifierFileName =
+            llvm::sys::path::filename(ModuleIdentifier);
+
         auto &ExportList = ExportLists[ModuleIdentifier];
 
         auto &DefinedGVSummaries = ModuleToDefinedGVSummaries[ModuleIdentifier];

               ProducedBinaries[count] = std::move(ErrOrBuffer.get());
             else
               ProducedBinaryFiles[count] = writeGeneratedObject(
-                  count, CacheEntryPath, *ErrOrBuffer.get());
+                  count, CacheEntryPath, *ErrOrBuffer.get(),
+                  moduleIdentifierFileName);
             return;
           }
         }

           return;
         }
         ProducedBinaryFiles[count] = writeGeneratedObject(
-            count, CacheEntryPath, *OutputBuffer);
+            count, CacheEntryPath, *OutputBuffer, moduleIdentifierFileName);
       }, IndexCount);
     }
   }

llvm/test/ThinLTO/X86/save_objects.ll

 ; RUN: ls %t.cache | count 3
 
 ; Check the name of object in directory has arch name included.
-; RUN: ls %t.thin.out | grep x86_64.thinlto.o | count 2
+; RUN: ls %t.thin.out | grep "x86_64\..*thinlto\.o" | count 2
 
 
 target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"