[NFC] Cleanup of EmitCXXGlobalInitFunc() and EmitCXXGlobalDtorFunc()

[Xiangling_L]

Summary

Tidy up some code of EmitCXXGlobalInitFunc() and EmitCXXGlobalDtorFunc()as the pre-work of [AIX][Frontend] Static init implementation for AIX considering no priority [https://reviews.llvm.org/D74166] patch.

[jasonliu]

clang/lib/CodeGen/CGDeclCXX.cpp

596

I think this patch is missing what @hubert.reinterpretcast mentioned in https://reviews.llvm.org/D74166?id=269900#inline-751064
which is an early return like this:

if (CXXGlobalInits.empty())
   return;

[Xiangling_L]

Minor change;

[jasonliu]

clang/lib/CodeGen/CGDeclCXX.cpp

596

Please double check the above early return is desired though. It seems even when CXXGlobalInits is empty, GenerateCXXGlobalInitFunc is trying to do a lot of things with Fn passed in. Later, we also called AddGlobalCtor(Fn). So a lot of behavior changes here, we want to make sure it's really 'NFC'.

[jasonliu]

clang/lib/CodeGen/CGDeclCXX.cpp

596

FYI,

class test {
  public:
        test();
};
test t1 __attribute__((init_priority (300)));

Compile with clang -target x86_64-apple-darwin10 -emit-llvm
With this change, I guess we will not generate @_GLOBAL__sub_I_d.cpp(), and also that function will not get added into @llvm.global_ctors.
I'm not sure if we really need @_GLOBAL__sub_I_d.cpp() on that platform in this case. But this change does not really qualify as NFC.
If we need to do this change, a test case is necessary, and we better ask people who familiar with the platform to confirm it's a desired change.

[Xiangling_L]

Remove early return part;

clang/lib/CodeGen/CGDeclCXX.cpp

596

Thanks, I am gonna remove this part and keep it as a NFC patch.

[jasonliu]

New diff does not have context available.

[Xiangling_L]

Add the context to the patch;

[jasonliu]

LGTM.

clang/lib/CodeGen/CGDeclCXX.cpp

596

Sure. Please update D74166 accordingly.

[hubert.reinterpretcast]

clang/lib/CodeGen/CGDeclCXX.cpp

600

In the less complex context of this patch, it seems this should just initialize FileName with getTransformedFileName(getModule()) by having getTransformedFileName return a SmallString<128> directly instead of a StringRef backed by a SmallString<128>. I think this would still translate well to D74166.

[Xiangling_L]

Address comments;

[hubert.reinterpretcast]

LGTM; thanks.

clang/lib/CodeGen/CGDeclCXX.cpp

   CXXThreadLocals.clear();
 }
 
+static StringRef getTransformedFileName(llvm::Module &M,
+                                        SmallString<128> &FileName) {
+  FileName = llvm::sys::path::filename(M.getName());
+
+  if (FileName.empty())
+    FileName = "<null>";
+
+  for (size_t i = 0; i < FileName.size(); ++i) {
+    // Replace everything that's not [a-zA-Z0-9._] with a _. This set happens
+    // to be the set of C preprocessing numbers.
+    if (!isPreprocessingNumberBody(FileName[i]))
+      FileName[i] = '_';
+  }
+
+  return FileName;
+}
+
 void
 CodeGenModule::EmitCXXGlobalInitFunc() {
   while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())

     PrioritizedCXXGlobalInits.clear();
   }
 
-  // Include the filename in the symbol name. Including "sub_" matches gcc and
-  // makes sure these symbols appear lexicographically behind the symbols with
-  // priority emitted above.
-  SmallString<128> FileName = llvm::sys::path::filename(getModule().getName());
-  if (FileName.empty())
-    FileName = "<null>";
-
-  for (size_t i = 0; i < FileName.size(); ++i) {
-    // Replace everything that's not [a-zA-Z0-9._] with a _. This set happens
-    // to be the set of C preprocessing numbers.
-    if (!isPreprocessingNumberBody(FileName[i]))
-      FileName[i] = '_';
-  }
-
+  // Include the filename in the symbol name. Including "sub_" matches gcc
+  // and makes sure these symbols appear lexicographically behind the symbols
+  // with priority emitted above.
+  SmallString<128> FileName;
   llvm::Function *Fn = CreateGlobalInitOrDestructFunction(
-      FTy, llvm::Twine("_GLOBAL__sub_I_", FileName), FI);
+      FTy,
+      llvm::Twine("_GLOBAL__sub_I_",
+                  getTransformedFileName(getModule(), FileName)),
+      FI);
 
   CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits);
   AddGlobalCtor(Fn);

 
   CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
   AddGlobalDtor(Fn);
+  CXXGlobalDtors.clear();
 }
 
 /// Emit the code necessary to initialize the given global variable.