Handle recursion in LLVMIRGeneration Timer

[davide]

Summary

See http://reviews.llvm.org/D20735 for more context.
Implementing this clang-side is not as terrible as I originally thought. Maybe needs a test case, but I wasn't able to reduce one easily (yet).

[vsk]

Comments on this patch -- The increment and decrement snippets seem like they could be pulled into helper methods. That should make it easier to update all users of LLVMIRGeneration. I wasn't able to come up with a regression test, but I do think this patch needs one.

Overall comments -- My main concern is that this isn't the only affected user of the Timer class. I have a preference for D20735 because it defines the underlying problem away. I'll defer to someone else on this (maybe @rafael?).

[vsk]

Ping, any updates on this patch?

[• rafael]

Since we found only one user, I think my preference is to handle it there.

Cheers,
Rafael

[davide]

ping?

[davide]

Richard, can you please take a look at this? The more I look at it the more it seems weird that we can recurse in this case, but I may miss something

clang/lib/CodeGen/CodeGenAction.cpp

     ASTContext *Context;
 
     Timer LLVMIRGeneration;
+    unsigned LLVMIRGenerationRefCount;
 
     std::unique_ptr<CodeGenerator> Gen;
 

         : Diags(Diags), Action(Action), CodeGenOpts(CodeGenOpts),
           TargetOpts(TargetOpts), LangOpts(LangOpts), AsmOutStream(OS),
           Context(nullptr), LLVMIRGeneration("LLVM IR Generation Time"),
+          LLVMIRGenerationRefCount(0),
           Gen(CreateLLVMCodeGen(Diags, InFile, HeaderSearchOpts, PPOpts,
                                 CodeGenOpts, C, CoverageInfo)) {
       llvm::TimePassesIsEnabled = TimePasses;

                                      Context->getSourceManager(),
                                      "LLVM IR generation of declaration");
 
-      if (llvm::TimePassesIsEnabled)
-        LLVMIRGeneration.startTimer();
+      // Recurse.
+      if (llvm::TimePassesIsEnabled) {
+        LLVMIRGenerationRefCount += 1;
+        if (LLVMIRGenerationRefCount == 1)
+          LLVMIRGeneration.startTimer();
+      }
 
       Gen->HandleTopLevelDecl(D);
 
-      if (llvm::TimePassesIsEnabled)
-        LLVMIRGeneration.stopTimer();
+      if (llvm::TimePassesIsEnabled) {
+        LLVMIRGenerationRefCount -= 1;
+        if (LLVMIRGenerationRefCount == 0)
+          LLVMIRGeneration.stopTimer();
+      }
 
       return true;
     }

     void HandleTranslationUnit(ASTContext &C) override {
       {
         PrettyStackTraceString CrashInfo("Per-file LLVM IR generation");
-        if (llvm::TimePassesIsEnabled)
-          LLVMIRGeneration.startTimer();
+        if (llvm::TimePassesIsEnabled) {
+          LLVMIRGenerationRefCount += 1;
+          if (LLVMIRGenerationRefCount == 1)
+            LLVMIRGeneration.startTimer();
+        }
 
         Gen->HandleTranslationUnit(C);
 
-        if (llvm::TimePassesIsEnabled)
-          LLVMIRGeneration.stopTimer();
+        if (llvm::TimePassesIsEnabled) {
+          LLVMIRGenerationRefCount -= 1;
+          if (LLVMIRGenerationRefCount == 0)
+            LLVMIRGeneration.stopTimer();
+        }
       }
 
       // Silently ignore if we weren't initialized for some reason.