[mips] Replace MipsABIEnum with a MipsABIInfo class.

[dsanders]

Summary

No functional change yet, it's just an object replacement for an enum.
It will allow us to gather ABI information in a single place so that we can
start testing for properties of the ABI's instead of the ABI itself.

For example we will eventually be able to use:

ABI.MinStackAlignmentInBytes()

instead of:

(isABI_N32() || isABI_N64()) ? 16 : 8

which is clearer and more maintainable.

[matheusalmeida]

LGTM.

[dsanders]

Rebased

[dsanders]

Refresh before commit.

lib/Target/Mips/Mips.td

 def FeatureFP64Bit     : SubtargetFeature<"fp64", "IsFP64bit", "true",
                                 "Support 64-bit FP registers.">;
 def FeatureFPXX        : SubtargetFeature<"fpxx", "IsFPXX", "true",
                                 "Support for FPXX.">;
 def FeatureNaN2008     : SubtargetFeature<"nan2008", "IsNaN2008bit", "true",
                                 "IEEE 754-2008 NaN encoding.">;
 def FeatureSingleFloat : SubtargetFeature<"single-float", "IsSingleFloat",
                                 "true", "Only supports single precision float">;
-def FeatureO32         : SubtargetFeature<"o32", "MipsABI", "O32",
+def FeatureO32         : SubtargetFeature<"o32", "ABI", "MipsABIInfo::O32()",
                                 "Enable o32 ABI">;
-def FeatureN32         : SubtargetFeature<"n32", "MipsABI", "N32",
+def FeatureN32         : SubtargetFeature<"n32", "ABI", "MipsABIInfo::N32()",
                                 "Enable n32 ABI">;
-def FeatureN64         : SubtargetFeature<"n64", "MipsABI", "N64",
+def FeatureN64         : SubtargetFeature<"n64", "ABI", "MipsABIInfo::N64()",
                                 "Enable n64 ABI">;
-def FeatureEABI        : SubtargetFeature<"eabi", "MipsABI", "EABI",
+def FeatureEABI        : SubtargetFeature<"eabi", "ABI", "MipsABIInfo::EABI()",
                                 "Enable eabi ABI">;
 def FeatureNoOddSPReg  : SubtargetFeature<"nooddspreg", "UseOddSPReg", "false",
                               "Disable odd numbered single-precision "
                               "registers">;
 def FeatureVFPU        : SubtargetFeature<"vfpu", "HasVFPU",
                                 "true", "Enable vector FPU instructions.">;
 def FeatureMips1       : SubtargetFeature<"mips1", "MipsArchVersion", "Mips1",
                                 "Mips I ISA Support [highly experimental]">;

lib/Target/Mips/MipsABIInfo.h

+//===---- MipsABIInfo.h - Information about MIPS ABI's --------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MIPSABIINFO_H
+#define MIPSABIINFO_H
+
+namespace llvm {
+class MipsABIInfo {
+public:
+  enum class ABI { Unknown, O32, N32, N64, EABI };
+
+protected:
+  ABI ThisABI;
+
+public:
+  MipsABIInfo(ABI ThisABI) : ThisABI(ThisABI) {}
+
+  static MipsABIInfo Unknown() { return MipsABIInfo(ABI::Unknown); }
+  static MipsABIInfo O32() { return MipsABIInfo(ABI::O32); }
+  static MipsABIInfo N32() { return MipsABIInfo(ABI::N32); }
+  static MipsABIInfo N64() { return MipsABIInfo(ABI::N64); }
+  static MipsABIInfo EABI() { return MipsABIInfo(ABI::EABI); }
+
+  bool IsKnown() const { return ThisABI != ABI::Unknown; }
+  bool IsO32() const { return ThisABI == ABI::O32; }
+  bool IsN32() const { return ThisABI == ABI::N32; }
+  bool IsN64() const { return ThisABI == ABI::N64; }
+  bool IsEABI() const { return ThisABI == ABI::EABI; }
+  ABI GetEnumValue() const { return ThisABI; }
+
+  /// Ordering of ABI's
+  /// MipsGenSubtargetInfo.inc will use this to resolve conflicts when given
+  /// multiple ABI options.
+  bool operator<(const MipsABIInfo Other) const {
+    return ThisABI < Other.GetEnumValue();
+  }
+};
+}
+
+#endif

lib/Target/Mips/MipsAsmPrinter.cpp

void MipsAsmPrinter::emitFrameDirective() {
   unsigned returnReg = RI.getRARegister();
   unsigned stackSize = MF->getFrameInfo()->getStackSize();
 
   getTargetStreamer().emitFrame(stackReg, stackSize, returnReg);
 }
 
 /// Emit Set directives.
 const char *MipsAsmPrinter::getCurrentABIString() const {
-  switch (Subtarget->getTargetABI()) {
-  case MipsSubtarget::O32:  return "abi32";
-  case MipsSubtarget::N32:  return "abiN32";
-  case MipsSubtarget::N64:  return "abi64";
-  case MipsSubtarget::EABI: return "eabi32"; // TODO: handle eabi64
+  switch (Subtarget->getABI().GetEnumValue()) {
+  case MipsABIInfo::ABI::O32:  return "abi32";
+  case MipsABIInfo::ABI::N32:  return "abiN32";
+  case MipsABIInfo::ABI::N64:  return "abi64";
+  case MipsABIInfo::ABI::EABI: return "eabi32"; // TODO: handle eabi64
   default: llvm_unreachable("Unknown Mips ABI");
   }
 }
 
 void MipsAsmPrinter::EmitFunctionEntryLabel() {
   MipsTargetStreamer &TS = getTargetStreamer();
 
   // NaCl sandboxing requires that indirect call instructions are masked.

lib/Target/Mips/MipsConstantIslandPass.cpp

namespace {
   std::vector<ImmBranch> ImmBranches;
 
   /// HasFarJump - True if any far jump instruction has been emitted during
   /// the branch fix up pass.
   bool HasFarJump;
 
   const TargetMachine &TM;
   bool IsPIC;
-  unsigned ABI;
   const MipsSubtarget *STI;
   const Mips16InstrInfo *TII;
   MipsFunctionInfo *MFI;
   MachineFunction *MF;
   MachineConstantPool *MCP;
 
   unsigned PICLabelUId;
   bool PrescannedForConstants;
 
   void initPICLabelUId(unsigned UId) {
     PICLabelUId = UId;
   }
 
 
   unsigned createPICLabelUId() {
     return PICLabelUId++;
   }
 
   public:
     static char ID;
     MipsConstantIslands(TargetMachine &tm)
         : MachineFunctionPass(ID), TM(tm),
-          IsPIC(TM.getRelocationModel() == Reloc::PIC_),
-          ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()), STI(nullptr),
+          IsPIC(TM.getRelocationModel() == Reloc::PIC_), STI(nullptr),
           MF(nullptr), MCP(nullptr), PrescannedForConstants(false) {}
 
     const char *getPassName() const override {
       return "Mips Constant Islands";
     }
 
     bool runOnMachineFunction(MachineFunction &F) override;
 

lib/Target/Mips/MipsLongBranch.cpp

namespace {
 
   class MipsLongBranch : public MachineFunctionPass {
 
   public:
     static char ID;
     MipsLongBranch(TargetMachine &tm)
       : MachineFunctionPass(ID), TM(tm),
         IsPIC(TM.getRelocationModel() == Reloc::PIC_),
-        ABI(TM.getSubtarget<MipsSubtarget>().getTargetABI()),
-        LongBranchSeqSize(!IsPIC ? 2 : (ABI == MipsSubtarget::N64 ? 10 :
+        ABI(TM.getSubtarget<MipsSubtarget>().getABI()),
+        LongBranchSeqSize(!IsPIC ? 2 : (ABI.IsN64() ? 10 :
             (!TM.getSubtarget<MipsSubtarget>().isTargetNaCl() ? 9 : 10))) {}
 
     const char *getPassName() const override {
       return "Mips Long Branch";
     }
 
     bool runOnMachineFunction(MachineFunction &F) override;
 
   private:
     void splitMBB(MachineBasicBlock *MBB);
     void initMBBInfo();
     int64_t computeOffset(const MachineInstr *Br);
     void replaceBranch(MachineBasicBlock &MBB, Iter Br, DebugLoc DL,
                        MachineBasicBlock *MBBOpnd);
     void expandToLongBranch(MBBInfo &Info);
 
     const TargetMachine &TM;
     MachineFunction *MF;
     SmallVector<MBBInfo, 16> MBBInfos;
     bool IsPIC;
-    unsigned ABI;
+    MipsABIInfo ABI;
     unsigned LongBranchSeqSize;
   };
 
   char MipsLongBranch::ID = 0;
 } // end of anonymous namespace
 
 /// createMipsLongBranchPass - Returns a pass that converts branches to long
 /// branches.
if (IsPIC) {
 
     // We must select between the MIPS32r6/MIPS64r6 BAL (which is a normal
     // instruction) and the pre-MIPS32r6/MIPS64r6 definition (which is an
     // pseudo-instruction wrapping BGEZAL).
 
     const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>();
     unsigned BalOp = Subtarget.hasMips32r6() ? Mips::BAL : Mips::BAL_BR;
 
-    if (ABI != MipsSubtarget::N64) {
+    if (!ABI.IsN64()) {
       // $longbr:
       //  addiu $sp, $sp, -8
       //  sw $ra, 0($sp)
       //  lui $at, %hi($tgt - $baltgt)
       //  bal $baltgt
       //  addiu $at, $at, %lo($tgt - $baltgt)
       // $baltgt:
       //  addu $at, $ra, $at

lib/Target/Mips/MipsSubtarget.h

 #include "MipsFrameLowering.h"
 #include "MipsISelLowering.h"
 #include "MipsInstrInfo.h"
 #include "MipsSelectionDAGInfo.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/MC/MCInstrItineraries.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
+#include "MipsABIInfo.h"
 #include <string>
 
 #define GET_SUBTARGETINFO_HEADER
 #include "MipsGenSubtargetInfo.inc"
 
 namespace llvm {
 class StringRef;
 
 class MipsTargetMachine;
 
 class MipsSubtarget : public MipsGenSubtargetInfo {
   virtual void anchor();
 
-public:
-  // NOTE: O64 will not be supported.
-  enum MipsABIEnum {
-    UnknownABI, O32, N32, N64, EABI
-  };
-
-protected:
   enum MipsArchEnum {
     Mips1, Mips2, Mips32, Mips32r2, Mips32r6, Mips3, Mips4, Mips5, Mips64,
     Mips64r2, Mips64r6
   };
 
   // Mips architecture version
   MipsArchEnum MipsArchVersion;
 
-  // Mips supported ABIs
-  MipsABIEnum MipsABI;
+  // Selected ABI
+  MipsABIInfo ABI;
 
   // IsLittle - The target is Little Endian
   bool IsLittle;
 
   // IsSingleFloat - The target only supports single precision float
   // point operations. This enable the target to use all 32 32-bit
   // floating point registers instead of only using even ones.
   bool IsSingleFloat;

 
 public:
   /// This overrides the PostRAScheduler bit in the SchedModel for each CPU.
   bool enablePostMachineScheduler() const override;
   void getCriticalPathRCs(RegClassVector &CriticalPathRCs) const override;
   CodeGenOpt::Level getOptLevelToEnablePostRAScheduler() const override;
 
   /// Only O32 and EABI supported right now.
-  bool isABI_EABI() const { return MipsABI == EABI; }
-  bool isABI_N64() const { return MipsABI == N64; }
-  bool isABI_N32() const { return MipsABI == N32; }
-  bool isABI_O32() const { return MipsABI == O32; }
+  bool isABI_EABI() const { return ABI.IsEABI(); }
+  bool isABI_N64() const { return ABI.IsN64(); }
+  bool isABI_N32() const { return ABI.IsN32(); }
+  bool isABI_O32() const { return ABI.IsO32(); }
   bool isABI_FPXX() const { return isABI_O32() && IsFPXX; }
-  unsigned getTargetABI() const { return MipsABI; }
+  const MipsABIInfo &getABI() const { return ABI; }
 
   /// This constructor initializes the data members to match that
   /// of the specified triple.
   MipsSubtarget(const std::string &TT, const std::string &CPU,
                 const std::string &FS, bool little,
                 const MipsTargetMachine *TM);
 
   /// ParseSubtargetFeatures - Parses features string setting specified

lib/Target/Mips/MipsSubtarget.cpp

static std::string computeDataLayout(const MipsSubtarget &ST) {
 
   return Ret;
 }
 
 MipsSubtarget::MipsSubtarget(const std::string &TT, const std::string &CPU,
                              const std::string &FS, bool little,
                              const MipsTargetMachine *_TM)
     : MipsGenSubtargetInfo(TT, CPU, FS), MipsArchVersion(Mips32),
-      MipsABI(UnknownABI), IsLittle(little), IsSingleFloat(false),
+      ABI(MipsABIInfo::Unknown()), IsLittle(little), IsSingleFloat(false),
       IsFPXX(false), NoABICalls(false), IsFP64bit(false), UseOddSPReg(true),
       IsNaN2008bit(false), IsGP64bit(false), HasVFPU(false), HasCnMips(false),
       IsLinux(true), HasMips3_32(false), HasMips3_32r2(false),
       HasMips4_32(false), HasMips4_32r2(false), HasMips5_32r2(false),
       InMips16Mode(false), InMips16HardFloat(Mips16HardFloat),
       InMicroMipsMode(false), HasDSP(false), HasDSPR2(false),
       AllowMixed16_32(Mixed16_32 | Mips_Os16), Os16(Mips_Os16),
       HasMSA(false), TM(_TM), TargetTriple(TT),
if (MipsArchVersion == Mips2)
     report_fatal_error("Code generation for MIPS-II is not implemented", false);
   if (MipsArchVersion == Mips3)
     report_fatal_error("Code generation for MIPS-III is not implemented",
                        false);
   if (MipsArchVersion == Mips5)
     report_fatal_error("Code generation for MIPS-V is not implemented", false);
 
   // Assert exactly one ABI was chosen.
-  assert(MipsABI != UnknownABI);
+  assert(ABI.IsKnown());
   assert((((getFeatureBits() & Mips::FeatureO32) != 0) +
           ((getFeatureBits() & Mips::FeatureEABI) != 0) +
           ((getFeatureBits() & Mips::FeatureN32) != 0) +
           ((getFeatureBits() & Mips::FeatureN64) != 0)) == 1);
 
   // Check if Architecture and ABI are compatible.
   assert(((!isGP64bit() && (isABI_O32() || isABI_EABI())) ||
           (isGP64bit() && (isABI_N32() || isABI_N64()))) &&