[mips] Move SpecialCallingConv to MipsCCState and use it from tablegen-erated code. NFC

[dsanders]

Summary

In the long run, it should probably become a calling convention in its own
right but for now just move it out of
MipsISelLowering::analyzeCallOperands() so that we can drop this function
in favour of CCState::AnalyzeCallOperands().

Depends on D6084

[dsanders]

David Chisnall requested (in D6117 - [mips] Promote i32 arguments to i64 for the N32/N64 ABI and fix <64-bit structs...) that this be committed and post-commit reviewed instead on the basis that it goes towards fixing a badly broken calling convention and there's nothing obviously wrong with the patches. I'm therefore going to go ahead and commit this.

[dsanders]

Closed by commit rL221517 (authored by @dsanders).

lib/Target/Mips/MipsCallingConv.td

def RetCC_Mips : CallingConv<[
   CCDelegateTo<RetCC_MipsO32>
 ]>;
 
 def CC_Mips_ByVal : CallingConv<[
   CCIfSubtarget<"isABI_O32()", CCIfByVal<CCPassByVal<4, 4>>>,
   CCIfByVal<CCPassByVal<8, 8>>
 ]>;
 
+def CC_Mips16RetHelper : CallingConv<[
+  CCIfByVal<CCDelegateTo<CC_Mips_ByVal>>,
+
+  // Integer arguments are passed in integer registers.
+  CCIfType<[i32], CCAssignToReg<[V0, V1, A0, A1]>>
+]>;
+
 def CC_Mips_FixedArg : CallingConv<[
+  // Mips16 needs special handling on some functions.
+  CCIf<"State.getCallingConv() != CallingConv::Fast",
+      CCIf<"static_cast<MipsCCState *>(&State)->getSpecialCallingConv() == "
+               "MipsCCState::Mips16RetHelperConv",
+           CCDelegateTo<CC_Mips16RetHelper>>>,
+
   CCIfByVal<CCDelegateTo<CC_Mips_ByVal>>,
 
   // f128 needs to be handled similarly to f32 and f64 on hard-float. However,
   // f128 is not legal and is lowered to i128 which is further lowered to a pair
   // of i64's.
   // This presents us with a problem for the calling convention since hard-float
   // still needs to pass them in FPU registers. We therefore resort to a
   // pre-analyze (see PreAnalyzeFormalArgsForF128()) step to pass information on
def CC_Mips_VarArg : CallingConv<[
   CCIfByVal<CCDelegateTo<CC_Mips_ByVal>>,
 
   // FIXME: There wasn't an EABI case in the original code and it seems unlikely
   //        that it's the same as CC_MipsN_VarArg
   CCIfSubtarget<"isABI_O32()", CCDelegateTo<CC_MipsO32_FP>>,
   CCDelegateTo<CC_MipsN_VarArg>
 ]>;
 
-//==
-
-def CC_Mips16RetHelper : CallingConv<[
-  CCIfByVal<CCDelegateTo<CC_Mips_ByVal>>,
-
-  // Integer arguments are passed in integer registers.
-  CCIfType<[i32], CCAssignToReg<[V0, V1, A0, A1]>>
-]>;
-
 //===----------------------------------------------------------------------===//
 // Callee-saved register lists.
 //===----------------------------------------------------------------------===//
 
 def CSR_SingleFloatOnly : CalleeSavedRegs<(add (sequence "F%u", 31, 20), RA, FP,
                                                (sequence "S%u", 7, 0))>;
 
 def CSR_O32_FPXX : CalleeSavedRegs<(add (sequence "D%u", 15, 10), RA, FP,

lib/Target/Mips/MipsISelLowering.h

getOpndList(SmallVectorImpl<SDValue> &Ops,
                 bool IsPICCall, bool GlobalOrExternal, bool InternalLinkage,
                 bool IsCallReloc, CallLoweringInfo &CLI, SDValue Callee,
                 SDValue Chain) const;
 
     /// MipsCC - This class provides methods used to analyze formal and call
     /// arguments and inquire about calling convention information.
     class MipsCC {
     public:
-      enum SpecialCallingConvType {
-        Mips16RetHelperConv, NoSpecialCallingConv
-      };
-
       MipsCC(CallingConv::ID CallConv, const MipsSubtarget &Subtarget,
              CCState &Info);
 
       void analyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
-                               const SDNode *CallNode,
                                std::vector<ArgListEntry> &FuncArgs,
                                CCState &State);
 
       /// reservedArgArea - The size of the area the caller reserves for
       /// register arguments. This is 16-byte if ABI is O32.
       unsigned reservedArgArea() const;
 
       /// Return pointer to array of integer argument registers.
       const ArrayRef<MCPhysReg> intArgRegs() const;
 
     private:
       /// Return the type of the register which is used to pass an argument or
       /// return a value. This function returns f64 if the argument is an i64
       /// value which has been generated as a result of softening an f128 value.
       /// Otherwise, it just returns VT.
       MVT getRegVT(MVT VT, const Type *OrigTy, const SDNode *CallNode,
                    bool IsSoftFloat) const;
 
-      SpecialCallingConvType getSpecialCallingConv(const SDNode *Callee) const;
-
       CallingConv::ID CallConv;
       const MipsSubtarget &Subtarget;
     };
   protected:
     SDValue lowerLOAD(SDValue Op, SelectionDAG &DAG) const;
     SDValue lowerSTORE(SDValue Op, SelectionDAG &DAG) const;
 
     // Subtarget Info

lib/Target/Mips/MipsISelLowering.cpp

static const MCPhysReg Mips64DPRegs[8] = {
   Mips::D12_64, Mips::D13_64, Mips::D14_64, Mips::D15_64,
   Mips::D16_64, Mips::D17_64, Mips::D18_64, Mips::D19_64
 };
 
 static bool originalTypeIsF128(const Type *Ty, const SDNode *CallNode);
 
 namespace {
 class MipsCCState : public CCState {
+public:
+  enum SpecialCallingConvType { Mips16RetHelperConv, NoSpecialCallingConv };
+
+  /// Determine the SpecialCallingConvType for the given callee
+  static SpecialCallingConvType
+  getSpecialCallingConvForCallee(const SDNode *Callee,
+                                 const MipsSubtarget &Subtarget) {
+    SpecialCallingConvType SpecialCallingConv = NoSpecialCallingConv;
+    if (Subtarget.inMips16HardFloat()) {
+      if (const GlobalAddressSDNode *G =
+              dyn_cast<const GlobalAddressSDNode>(Callee)) {
+        llvm::StringRef Sym = G->getGlobal()->getName();
+        Function *F = G->getGlobal()->getParent()->getFunction(Sym);
+        if (F && F->hasFnAttribute("__Mips16RetHelper")) {
+          SpecialCallingConv = Mips16RetHelperConv;
+        }
+      }
+    }
+    return SpecialCallingConv;
+  }
+
 private:
   /// Identify lowered values that originated from f128 arguments and record
   /// this for use by RetCC_MipsN.
   void
   PreAnalyzeCallResultForF128(const SmallVectorImpl<ISD::InputArg> &Ins,
                               const TargetLowering::CallLoweringInfo &CLI) {
     for (unsigned i = 0; i < Ins.size(); ++i)
       OriginalArgWasF128.push_back(
for (unsigned i = 0; i < Ins.size(); ++i) {
       OriginalArgWasF128.push_back(
           originalTypeIsF128(FuncArg->getType(), nullptr));
     }
   }
 
   /// Records whether the value has been lowered from an f128.
   SmallVector<bool, 4> OriginalArgWasF128;
 
+  // Used to handle MIPS16-specific calling convention tweaks.
+  // FIXME: This should probably be a fully fledged calling convention.
+  SpecialCallingConvType SpecialCallingConv;
+
 public:
   // FIXME: Remove this from a public inteface ASAP. It's a temporary trap door
   //        to allow analyzeCallOperands to be removed incrementally.
   void PreAnalyzeCallOperandsForF128_(
       const SmallVectorImpl<ISD::OutputArg> &Outs,
       std::vector<TargetLowering::ArgListEntry> &FuncArgs, SDNode *CallNode) {
     PreAnalyzeCallOperandsForF128(Outs, FuncArgs, CallNode);
   }
   // FIXME: Remove this from a public inteface ASAP. It's a temporary trap door
   //        to clean up after the above functions.
   void ClearOriginalArgWasF128() { OriginalArgWasF128.clear(); }
 
   MipsCCState(CallingConv::ID CC, bool isVarArg, MachineFunction &MF,
-              SmallVectorImpl<CCValAssign> &locs, LLVMContext &C)
-      : CCState(CC, isVarArg, MF, locs, C) {}
+              SmallVectorImpl<CCValAssign> &locs, LLVMContext &C,
+              SpecialCallingConvType SpecialCC = NoSpecialCallingConv)
+      : CCState(CC, isVarArg, MF, locs, C), SpecialCallingConv(SpecialCC) {}
 
   void AnalyzeFormalArguments(const SmallVectorImpl<ISD::InputArg> &Ins,
                               CCAssignFn Fn) {
     PreAnalyzeFormalArgumentsForF128(Ins);
     CCState::AnalyzeFormalArguments(Ins, Fn);
     OriginalArgWasF128.clear();
   }
 
bool CheckReturn(const SmallVectorImpl<ISD::OutputArg> &ArgsFlags,
                    CCAssignFn Fn) {
     PreAnalyzeReturnForF128(ArgsFlags);
     bool Return = CCState::CheckReturn(ArgsFlags, Fn);
     OriginalArgWasF128.clear();
     return Return;
   }
 
   bool WasOriginalArgF128(unsigned ValNo) { return OriginalArgWasF128[ValNo]; }
+  SpecialCallingConvType getSpecialCallingConv() { return SpecialCallingConv; }
 };
 }
 
 // If I is a shifted mask, set the size (Size) and the first bit of the
 // mask (Pos), and return true.
 // For example, if I is 0x003ff800, (Pos, Size) = (11, 11).
 static bool isShiftedMask(uint64_t I, uint64_t &Pos, uint64_t &Size) {
   if (!isShiftedMask_64(I))
MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   MachineFunction &MF = DAG.getMachineFunction();
   MachineFrameInfo *MFI = MF.getFrameInfo();
   const TargetFrameLowering *TFL = MF.getSubtarget().getFrameLowering();
   MipsFunctionInfo *FuncInfo = MF.getInfo<MipsFunctionInfo>();
   bool IsPIC = getTargetMachine().getRelocationModel() == Reloc::PIC_;
 
   // Analyze operands of the call, assigning locations to each operand.
   SmallVector<CCValAssign, 16> ArgLocs;
-  MipsCCState CCInfo(CallConv, IsVarArg, DAG.getMachineFunction(), ArgLocs,
-                     *DAG.getContext());
+  MipsCCState CCInfo(
+      CallConv, IsVarArg, DAG.getMachineFunction(), ArgLocs, *DAG.getContext(),
+      MipsCCState::getSpecialCallingConvForCallee(Callee.getNode(), Subtarget));
   MipsCC MipsCCInfo(CallConv, Subtarget, CCInfo);
 
   CCInfo.PreAnalyzeCallOperandsForF128_(Outs, CLI.getArgs(), Callee.getNode());
-  MipsCCInfo.analyzeCallOperands(Outs, Callee.getNode(), CLI.getArgs(), CCInfo);
+  MipsCCInfo.analyzeCallOperands(Outs, CLI.getArgs(), CCInfo);
   CCInfo.ClearOriginalArgWasF128();
 
   // Get a count of how many bytes are to be pushed on the stack.
   unsigned NextStackOffset = CCInfo.getNextStackOffset();
 
   // Check if it's really possible to do a tail call.
   if (IsTailCall)
     IsTailCall = isEligibleForTailCallOptimization(
static bool originalTypeIsF128(const Type *Ty, const SDNode *CallNode) {
   const ExternalSymbolSDNode *ES =
     dyn_cast_or_null<const ExternalSymbolSDNode>(CallNode);
 
   // If the Ty is i128 and the function being called is a long double emulation
   // routine, then the original type is f128.
   return (ES && Ty->isIntegerTy(128) && isF128SoftLibCall(ES->getSymbol()));
 }
 
-MipsTargetLowering::MipsCC::SpecialCallingConvType
-MipsTargetLowering::MipsCC::getSpecialCallingConv(const SDNode *Callee) const {
-  MipsCC::SpecialCallingConvType SpecialCallingConv =
-    MipsCC::NoSpecialCallingConv;
-  if (Subtarget.inMips16HardFloat()) {
-    if (const GlobalAddressSDNode *G =
-            dyn_cast<const GlobalAddressSDNode>(Callee)) {
-      llvm::StringRef Sym = G->getGlobal()->getName();
-      Function *F = G->getGlobal()->getParent()->getFunction(Sym);
-      if (F && F->hasFnAttribute("__Mips16RetHelper")) {
-        SpecialCallingConv = MipsCC::Mips16RetHelperConv;
-      }
-    }
-  }
-  return SpecialCallingConv;
-}
-
 MipsTargetLowering::MipsCC::MipsCC(CallingConv::ID CC,
                                    const MipsSubtarget &Subtarget_,
                                    CCState &Info)
     : CallConv(CC), Subtarget(Subtarget_) {
   // Pre-allocate reserved argument area.
   Info.AllocateStack(reservedArgArea(), 1);
 }
 
 void MipsTargetLowering::MipsCC::analyzeCallOperands(
-    const SmallVectorImpl<ISD::OutputArg> &Args, const SDNode *CallNode,
+    const SmallVectorImpl<ISD::OutputArg> &Args,
     std::vector<ArgListEntry> &FuncArgs, CCState &State) {
-  MipsCC::SpecialCallingConvType SpecialCallingConv =
-      getSpecialCallingConv(CallNode);
   assert((CallConv != CallingConv::Fast || !State.isVarArg()) &&
          "CallingConv::Fast shouldn't be used for vararg functions.");
 
   unsigned NumOpnds = Args.size();
-  llvm::CCAssignFn *FixedFn = CC_Mips_FixedArg;
-  if (CallConv != CallingConv::Fast &&
-      SpecialCallingConv == Mips16RetHelperConv)
-    FixedFn = CC_Mips16RetHelper;
 
   for (unsigned I = 0; I != NumOpnds; ++I) {
     MVT ArgVT = Args[I].VT;
     ISD::ArgFlagsTy ArgFlags = Args[I].Flags;
     bool R;
 
     if (State.isVarArg() && !Args[I].IsFixed)
       R = CC_Mips_VarArg(I, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, State);
     else
-      R = FixedFn(I, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, State);
+      R = CC_Mips_FixedArg(I, ArgVT, ArgVT, CCValAssign::Full, ArgFlags, State);
 
     if (R) {
 #ifndef NDEBUG
       dbgs() << "Call operand #" << I << " has unhandled type "
              << EVT(ArgVT).getEVTString();
 #endif
       llvm_unreachable(nullptr);
     }