Cleanups for getKindForGlobal:

- Clarify block comment
 - Make Function/GlobalVariable split more explicit.
 - Move locals closer to uses.

llvm-svn: 333356

llvm/lib/Target/TargetLoweringObjectFile.cpp

@@ -138,22 +138,21 @@ void TargetLoweringObjectFile::emitPersonalityValue(MCStreamer &Streamer,
 
 
 /// getKindForGlobal - This is a top-level target-independent classifier for
-/// a global variable.  Given an global variable and information from TM, it
-/// classifies the global in a variety of ways that make various target
-/// implementations simpler.  The target implementation is free to ignore this
-/// extra info of course.
+/// a global object.  Given a global variable and information from the TM, this
+/// function classifies the global in a target independent manner. This function
+/// may be overridden by the target implementation.
 SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalObject *GO,
                                                        const TargetMachine &TM){
   assert(!GO->isDeclaration() && !GO->hasAvailableExternallyLinkage() &&
          "Can only be used for global definitions");
 
-  Reloc::Model ReloModel = TM.getRelocationModel();
-
-  // Early exit - functions should be always in text sections.
-  const auto *GVar = dyn_cast<GlobalVariable>(GO);
-  if (!GVar)
+  // Functions are classified as text sections.
+  if (isa<Function>(GO))
     return SectionKind::getText();
 
+  // Global variables require more detailed analysis.
+  const auto *GVar = cast<GlobalVariable>(GO);
+
   // Handle thread-local data first.
   if (GVar->isThreadLocal()) {
     if (isSuitableForBSS(GVar, TM.Options.NoZerosInBSS))
@@ -174,14 +173,13 @@ SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalObject *GO,
     return SectionKind::getBSS();
   }
 
-  const Constant *C = GVar->getInitializer();
-
   // If the global is marked constant, we can put it into a mergable section,
   // a mergable string section, or general .data if it contains relocations.
   if (GVar->isConstant()) {
     // If the initializer for the global contains something that requires a
     // relocation, then we may have to drop this into a writable data section
     // even though it is marked const.
+    const Constant *C = GVar->getInitializer();
     if (!C->needsRelocation()) {
       // If the global is required to have a unique address, it can't be put
       // into a mergable section: just drop it into the general read-only
@@ -227,6 +225,7 @@ SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalObject *GO,
       // the time the app starts up.  However, we can't put this into a
       // mergable section, because the linker doesn't take relocations into
       // consideration when it tries to merge entries in the section.
+      Reloc::Model ReloModel = TM.getRelocationModel();
       if (ReloModel == Reloc::Static || ReloModel == Reloc::ROPI ||
           ReloModel == Reloc::RWPI || ReloModel == Reloc::ROPI_RWPI)
         return SectionKind::getReadOnly();