[LTO] Expose opt() in LTOBackend (NFC).

[fhahn]

Summary

Exposing opt() which runs middle-end LTO optimzation allows re-using it
in LTOCodeGenerator.

[steven_wu]

LGTM with a small comment.

llvm/lib/LTO/LTOBackend.cpp

486

Any reason why the function need to be moved instead of just renamed? I will reduce the diff if possible.

[fhahn]

llvm/lib/LTO/LTOBackend.cpp

486

Unfortunately it is originally defined in a anonymous namespace, so I think it has to be moved out of that to be defined in lto::.

[dexonsmith]

llvm/lib/LTO/LTOBackend.cpp

486

[drive-by comments]

I think just adding the lto:: should do the right thing. If not, you can temporarily close the anonymous namespace and reopen it.

Another option is an NFC prep commit that limits the anonymous namespace to .cpp-declared structures, and adds a static keyword on each function that's no longer "anonymous". That'd match the more typical LLVM style... reducing this patch to s/static bool opt/bool lto::opt/.

[fhahn]

Rebased after f638c2eb4ee6d0a0bd0e80cd305ad93e382db8f5, which removed the anonymous namespace (it just included function definitions), thanks for the tip!

Now the diff boils down to just changing the name.

[fhahn]

llvm/lib/LTO/LTOBackend.cpp

486

Another option is an NFC prep commit that limits the anonymous namespace to .cpp-declared structures, and adds a static keyword on each function that's no longer "anonymous". That'd match the more typical LLVM style... reducing this patch to s/static bool opt/bool lto::opt/.

Ah yes, LLVM style suggests to only use anonymous namespaces for class declarations! I went with this suggestion and removed the anonymous namespace in f638c2eb4ee6d0a0bd0e80cd305ad93e382db8f5, because it just contained function definitions.

[steven_wu]

LGTM!

llvm/include/llvm/LTO/LTOBackend.h

 
 class BitcodeModule;
 class Error;
 class Module;
 class Target;
 
 namespace lto {
 
+/// Runs middle-end LTO optimizations on \p Mod.
+bool opt(const Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
+         bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
+         const ModuleSummaryIndex *ImportSummary,
+         const std::vector<uint8_t> &CmdArgs);
+
 /// Runs a regular LTO backend. The regular LTO backend can also act as the
 /// regular LTO phase of ThinLTO, which may need to access the combined index.
 Error backend(const Config &C, AddStreamFn AddStream,
               unsigned ParallelCodeGenParallelismLevel,
               std::unique_ptr<Module> M, ModuleSummaryIndex &CombinedIndex);
 
 /// Runs a ThinLTO backend.
 Error thinBackend(const Config &C, unsigned Task, AddStreamFn AddStream,

llvm/lib/LTO/LTOBackend.cpp

static void runOldPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
   }
   if (IsThinLTO)
     PMB.populateThinLTOPassManager(passes);
   else
     PMB.populateLTOPassManager(passes);
   passes.run(Mod);
 }
 
-bool opt(const Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
-         bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
-         const ModuleSummaryIndex *ImportSummary,
-         const std::vector<uint8_t> &CmdArgs) {
-  if (EmbedBitcode == LTOBitcodeEmbedding::EmbedPostMergePreOptimized) {
-    // FIXME: the motivation for capturing post-merge bitcode and command line
-    // is replicating the compilation environment from bitcode, without needing
-    // to understand the dependencies (the functions to be imported). This
-    // assumes a clang - based invocation, case in which we have the command
-    // line.
-    // It's not very clear how the above motivation would map in the
-    // linker-based case, so we currently don't plumb the command line args in
-    // that case.
-    if (CmdArgs.empty())
-      LLVM_DEBUG(
-          dbgs() << "Post-(Thin)LTO merge bitcode embedding was requested, but "
-                    "command line arguments are not available");
-    llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
-                               /*EmbedBitcode*/ true, /*EmbedCmdline*/ true,
-                               /*Cmdline*/ CmdArgs);
-  }
-  // FIXME: Plumb the combined index into the new pass manager.
-  if (!Conf.OptPipeline.empty())
-    runNewPMCustomPasses(Conf, Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
-                         Conf.DisableVerify);
-  else if (Conf.UseNewPM)
-    runNewPMPasses(Conf, Mod, TM, Conf.OptLevel, IsThinLTO, ExportSummary,
-                   ImportSummary);
-  else
-    runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary);
-  return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
-}
-
 void codegen(const Config &Conf, TargetMachine *TM, AddStreamFn AddStream,
              unsigned Task, Module &Mod,
              const ModuleSummaryIndex &CombinedIndex) {
   if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod))
     return;
 
   if (EmbedBitcode == LTOBitcodeEmbedding::EmbedOptimized)
     llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
Error lto::finalizeOptimizationRemarks(
   // call the global destructors before exiting.
   if (!DiagOutputFile)
     return Error::success();
   DiagOutputFile->keep();
   DiagOutputFile->os().flush();
   return Error::success();
 }
 
+bool lto::opt(const Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
+              bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
+              const ModuleSummaryIndex *ImportSummary,
+              const std::vector<uint8_t> &CmdArgs) {
+  if (EmbedBitcode == LTOBitcodeEmbedding::EmbedPostMergePreOptimized) {
+    // FIXME: the motivation for capturing post-merge bitcode and command line
+    // is replicating the compilation environment from bitcode, without needing
+    // to understand the dependencies (the functions to be imported). This
+    // assumes a clang - based invocation, case in which we have the command
+    // line.
+    // It's not very clear how the above motivation would map in the
+    // linker-based case, so we currently don't plumb the command line args in
+    // that case.
+    if (CmdArgs.empty())
+      LLVM_DEBUG(
+          dbgs() << "Post-(Thin)LTO merge bitcode embedding was requested, but "
+                    "command line arguments are not available");
+    llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
+                               /*EmbedBitcode*/ true, /*EmbedCmdline*/ true,
+                               /*Cmdline*/ CmdArgs);
+  }
+  // FIXME: Plumb the combined index into the new pass manager.
+  if (!Conf.OptPipeline.empty())
+    runNewPMCustomPasses(Conf, Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
+                         Conf.DisableVerify);
+  else if (Conf.UseNewPM)
+    runNewPMPasses(Conf, Mod, TM, Conf.OptLevel, IsThinLTO, ExportSummary,
+                   ImportSummary);
+  else
+    runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary);
+  return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
+}
+
 Error lto::backend(const Config &C, AddStreamFn AddStream,
                    unsigned ParallelCodeGenParallelismLevel,
                    std::unique_ptr<Module> Mod,
                    ModuleSummaryIndex &CombinedIndex) {
   Expected<const Target *> TOrErr = initAndLookupTarget(C, *Mod);
   if (!TOrErr)
     return TOrErr.takeError();