[Codegen] Reorganize PICLevel

[davide]

Summary

See http://reviews.llvm.org/D21100 for context/rationale behind this change.
CC:ing PPC as it seems to be the only user of this feature.

[• rafael]

LGTM with a comment in CodeGen.h saying this maps -fpic/-fPIC. Please
also improve the commit message to mention that Default is being
converted to NotPIC so that target independent code can reason about
this.

include/llvm/Support/CodeGen.h

namespace llvm {
 
   // Code model types.
   namespace CodeModel {
     // Sync changes with CodeGenCWrappers.h.
     enum Model { Default, JITDefault, Small, Kernel, Medium, Large };
   }
 
   namespace PICLevel {
-    enum Level { Default=0, Small=1, Large=2 };
+    enum Level { NotPIC=0, SmallPIC=1, BigPic=2 };
   }
 
   namespace PIELevel {
     enum Level { Default=0, Small=1, Large=2 };
   }
 
   // TLS models.
   namespace TLSModel {

lib/IR/Module.cpp

Comdat *Module::getOrInsertComdat(StringRef Name) {
   Entry.second.Name = &Entry;
   return &Entry.second;
 }
 
 PICLevel::Level Module::getPICLevel() const {
   auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("PIC Level"));
 
   if (!Val)
-    return PICLevel::Default;
+    return PICLevel::NotPIC;
 
   return static_cast<PICLevel::Level>(
       cast<ConstantInt>(Val->getValue())->getZExtValue());
 }
 
 void Module::setPICLevel(PICLevel::Level PL) {
   addModuleFlag(ModFlagBehavior::Error, "PIC Level", PL);
 }

lib/Target/PowerPC/PPCAsmPrinter.cpp

       MOSymbol = getSymbol(MO.getGlobal());
     else if (MO.isCPI())
       MOSymbol = GetCPISymbol(MO.getIndex());
     else if (MO.isJTI())
       MOSymbol = GetJTISymbol(MO.getIndex());
     else if (MO.isBlockAddress())
       MOSymbol = GetBlockAddressSymbol(MO.getBlockAddress());
 
-    if (PL == PICLevel::Small) {
+    if (PL == PICLevel::SmallPIC) {
       const MCExpr *Exp =
         MCSymbolRefExpr::create(MOSymbol, MCSymbolRefExpr::VK_GOT,
                                 OutContext);
       TmpInst.getOperand(1) = MCOperand::createExpr(Exp);
     } else {
       MCSymbol *TOCEntry = lookUpOrCreateTOCEntry(MOSymbol);
 
       const MCExpr *Exp =

     if (TS)
       TS->emitAbiVersion(2);
   }
 
   if (static_cast<const PPCTargetMachine &>(TM).isPPC64() ||
       TM.getRelocationModel() != Reloc::PIC_)
     return AsmPrinter::EmitStartOfAsmFile(M);
 
-  if (M.getPICLevel() == PICLevel::Small)
+  if (M.getPICLevel() == PICLevel::SmallPIC)
     return AsmPrinter::EmitStartOfAsmFile(M);
 
   OutStreamer->SwitchSection(OutContext.getELFSection(
       ".got2", ELF::SHT_PROGBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC));
 
   MCSymbol *TOCSym = OutContext.getOrCreateSymbol(Twine(".LTOC"));
   MCSymbol *CurrentPos = OutContext.createTempSymbol();
 

 
   OutStreamer->SwitchSection(getObjFileLowering().getTextSection());
 }
 
 void PPCLinuxAsmPrinter::EmitFunctionEntryLabel() {
   // linux/ppc32 - Normal entry label.
   if (!Subtarget->isPPC64() &&
       (TM.getRelocationModel() != Reloc::PIC_ ||
-       MF->getFunction()->getParent()->getPICLevel() == PICLevel::Small))
+       MF->getFunction()->getParent()->getPICLevel() == PICLevel::SmallPIC))
     return AsmPrinter::EmitFunctionEntryLabel();
 
   if (!Subtarget->isPPC64()) {
     const PPCFunctionInfo *PPCFI = MF->getInfo<PPCFunctionInfo>();
     if (PPCFI->usesPICBase()) {
       MCSymbol *RelocSymbol = PPCFI->getPICOffsetSymbol();
       MCSymbol *PICBase = MF->getPICBaseSymbol();
       OutStreamer->EmitLabel(RelocSymbol);

lib/Target/PowerPC/PPCISelDAGToDAG.cpp

if (!GlobalBaseReg) {
     MachineBasicBlock &FirstMBB = MF->front();
     MachineBasicBlock::iterator MBBI = FirstMBB.begin();
     const Module *M = MF->getFunction()->getParent();
     DebugLoc dl;
 
     if (PPCLowering->getPointerTy(CurDAG->getDataLayout()) == MVT::i32) {
       if (PPCSubTarget->isTargetELF()) {
         GlobalBaseReg = PPC::R30;
-        if (M->getPICLevel() == PICLevel::Small) {
+        if (M->getPICLevel() == PICLevel::SmallPIC) {
           BuildMI(FirstMBB, MBBI, dl, TII.get(PPC::MoveGOTtoLR));
           BuildMI(FirstMBB, MBBI, dl, TII.get(PPC::MFLR), GlobalBaseReg);
           MF->getInfo<PPCFunctionInfo>()->setUsesPICBase(true);
         } else {
           BuildMI(FirstMBB, MBBI, dl, TII.get(PPC::MovePCtoLR));
           BuildMI(FirstMBB, MBBI, dl, TII.get(PPC::MFLR), GlobalBaseReg);
           unsigned TempReg = RegInfo->createVirtualRegister(&PPC::GPRCRegClass);
           BuildMI(FirstMBB, MBBI, dl,

lib/Target/PowerPC/PPCISelLowering.cpp

     SDValue TGA = DAG.getTargetGlobalAddress(GV, dl, PtrVT, 0, 0);
     SDValue GOTPtr;
     if (is64bit) {
       setUsesTOCBasePtr(DAG);
       SDValue GOTReg = DAG.getRegister(PPC::X2, MVT::i64);
       GOTPtr = DAG.getNode(PPCISD::ADDIS_TLSGD_HA, dl, PtrVT,
                                    GOTReg, TGA);
     } else {
-      if (picLevel == PICLevel::Small)
+      if (picLevel == PICLevel::SmallPIC)
         GOTPtr = DAG.getNode(PPCISD::GlobalBaseReg, dl, PtrVT);
       else
         GOTPtr = DAG.getNode(PPCISD::PPC32_PICGOT, dl, PtrVT);
     }
     return DAG.getNode(PPCISD::ADDI_TLSGD_L_ADDR, dl, PtrVT,
                        GOTPtr, TGA, TGA);
   }
 
   if (Model == TLSModel::LocalDynamic) {
     SDValue TGA = DAG.getTargetGlobalAddress(GV, dl, PtrVT, 0, 0);
     SDValue GOTPtr;
     if (is64bit) {
       setUsesTOCBasePtr(DAG);
       SDValue GOTReg = DAG.getRegister(PPC::X2, MVT::i64);
       GOTPtr = DAG.getNode(PPCISD::ADDIS_TLSLD_HA, dl, PtrVT,
                            GOTReg, TGA);
     } else {
-      if (picLevel == PICLevel::Small)
+      if (picLevel == PICLevel::SmallPIC)
         GOTPtr = DAG.getNode(PPCISD::GlobalBaseReg, dl, PtrVT);
       else
         GOTPtr = DAG.getNode(PPCISD::PPC32_PICGOT, dl, PtrVT);
     }
     SDValue TLSAddr = DAG.getNode(PPCISD::ADDI_TLSLD_L_ADDR, dl,
                                   PtrVT, GOTPtr, TGA, TGA);
     SDValue DtvOffsetHi = DAG.getNode(PPCISD::ADDIS_DTPREL_HA, dl,
                                       PtrVT, TLSAddr, TGA);