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      1 //===-- llvm/CallingConvLower.h - Calling Conventions -----------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file declares the CCState and CCValAssign classes, used for lowering
     11 // and implementing calling conventions.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_CODEGEN_CALLINGCONVLOWER_H
     16 #define LLVM_CODEGEN_CALLINGCONVLOWER_H
     17 
     18 #include "llvm/ADT/SmallVector.h"
     19 #include "llvm/CodeGen/MachineFunction.h"
     20 #include "llvm/CodeGen/ValueTypes.h"
     21 #include "llvm/Target/TargetCallingConv.h"
     22 #include "llvm/CallingConv.h"
     23 
     24 namespace llvm {
     25   class TargetRegisterInfo;
     26   class TargetMachine;
     27   class CCState;
     28 
     29 /// CCValAssign - Represent assignment of one arg/retval to a location.
     30 class CCValAssign {
     31 public:
     32   enum LocInfo {
     33     Full,   // The value fills the full location.
     34     SExt,   // The value is sign extended in the location.
     35     ZExt,   // The value is zero extended in the location.
     36     AExt,   // The value is extended with undefined upper bits.
     37     BCvt,   // The value is bit-converted in the location.
     38     VExt,   // The value is vector-widened in the location.
     39             // FIXME: Not implemented yet. Code that uses AExt to mean
     40             // vector-widen should be fixed to use VExt instead.
     41     Indirect // The location contains pointer to the value.
     42     // TODO: a subset of the value is in the location.
     43   };
     44 private:
     45   /// ValNo - This is the value number begin assigned (e.g. an argument number).
     46   unsigned ValNo;
     47 
     48   /// Loc is either a stack offset or a register number.
     49   unsigned Loc;
     50 
     51   /// isMem - True if this is a memory loc, false if it is a register loc.
     52   bool isMem : 1;
     53 
     54   /// isCustom - True if this arg/retval requires special handling.
     55   bool isCustom : 1;
     56 
     57   /// Information about how the value is assigned.
     58   LocInfo HTP : 6;
     59 
     60   /// ValVT - The type of the value being assigned.
     61   MVT ValVT;
     62 
     63   /// LocVT - The type of the location being assigned to.
     64   MVT LocVT;
     65 public:
     66 
     67   static CCValAssign getReg(unsigned ValNo, MVT ValVT,
     68                             unsigned RegNo, MVT LocVT,
     69                             LocInfo HTP) {
     70     CCValAssign Ret;
     71     Ret.ValNo = ValNo;
     72     Ret.Loc = RegNo;
     73     Ret.isMem = false;
     74     Ret.isCustom = false;
     75     Ret.HTP = HTP;
     76     Ret.ValVT = ValVT;
     77     Ret.LocVT = LocVT;
     78     return Ret;
     79   }
     80 
     81   static CCValAssign getCustomReg(unsigned ValNo, MVT ValVT,
     82                                   unsigned RegNo, MVT LocVT,
     83                                   LocInfo HTP) {
     84     CCValAssign Ret;
     85     Ret = getReg(ValNo, ValVT, RegNo, LocVT, HTP);
     86     Ret.isCustom = true;
     87     return Ret;
     88   }
     89 
     90   static CCValAssign getMem(unsigned ValNo, MVT ValVT,
     91                             unsigned Offset, MVT LocVT,
     92                             LocInfo HTP) {
     93     CCValAssign Ret;
     94     Ret.ValNo = ValNo;
     95     Ret.Loc = Offset;
     96     Ret.isMem = true;
     97     Ret.isCustom = false;
     98     Ret.HTP = HTP;
     99     Ret.ValVT = ValVT;
    100     Ret.LocVT = LocVT;
    101     return Ret;
    102   }
    103 
    104   static CCValAssign getCustomMem(unsigned ValNo, MVT ValVT,
    105                                   unsigned Offset, MVT LocVT,
    106                                   LocInfo HTP) {
    107     CCValAssign Ret;
    108     Ret = getMem(ValNo, ValVT, Offset, LocVT, HTP);
    109     Ret.isCustom = true;
    110     return Ret;
    111   }
    112 
    113   unsigned getValNo() const { return ValNo; }
    114   MVT getValVT() const { return ValVT; }
    115 
    116   bool isRegLoc() const { return !isMem; }
    117   bool isMemLoc() const { return isMem; }
    118 
    119   bool needsCustom() const { return isCustom; }
    120 
    121   unsigned getLocReg() const { assert(isRegLoc()); return Loc; }
    122   unsigned getLocMemOffset() const { assert(isMemLoc()); return Loc; }
    123   MVT getLocVT() const { return LocVT; }
    124 
    125   LocInfo getLocInfo() const { return HTP; }
    126   bool isExtInLoc() const {
    127     return (HTP == AExt || HTP == SExt || HTP == ZExt);
    128   }
    129 
    130 };
    131 
    132 /// CCAssignFn - This function assigns a location for Val, updating State to
    133 /// reflect the change.  It returns 'true' if it failed to handle Val.
    134 typedef bool CCAssignFn(unsigned ValNo, MVT ValVT,
    135                         MVT LocVT, CCValAssign::LocInfo LocInfo,
    136                         ISD::ArgFlagsTy ArgFlags, CCState &State);
    137 
    138 /// CCCustomFn - This function assigns a location for Val, possibly updating
    139 /// all args to reflect changes and indicates if it handled it. It must set
    140 /// isCustom if it handles the arg and returns true.
    141 typedef bool CCCustomFn(unsigned &ValNo, MVT &ValVT,
    142                         MVT &LocVT, CCValAssign::LocInfo &LocInfo,
    143                         ISD::ArgFlagsTy &ArgFlags, CCState &State);
    144 
    145 /// ParmContext - This enum tracks whether calling convention lowering is in
    146 /// the context of prologue or call generation. Not all backends make use of
    147 /// this information.
    148 typedef enum { Unknown, Prologue, Call } ParmContext;
    149 
    150 /// CCState - This class holds information needed while lowering arguments and
    151 /// return values.  It captures which registers are already assigned and which
    152 /// stack slots are used.  It provides accessors to allocate these values.
    153 class CCState {
    154 private:
    155   CallingConv::ID CallingConv;
    156   bool IsVarArg;
    157   MachineFunction &MF;
    158   const TargetMachine &TM;
    159   const TargetRegisterInfo &TRI;
    160   SmallVector<CCValAssign, 16> &Locs;
    161   LLVMContext &Context;
    162 
    163   unsigned StackOffset;
    164   SmallVector<uint32_t, 16> UsedRegs;
    165   unsigned FirstByValReg;
    166   bool FirstByValRegValid;
    167 
    168 protected:
    169   ParmContext CallOrPrologue;
    170 
    171 public:
    172   CCState(CallingConv::ID CC, bool isVarArg, MachineFunction &MF,
    173           const TargetMachine &TM, SmallVector<CCValAssign, 16> &locs,
    174           LLVMContext &C);
    175 
    176   void addLoc(const CCValAssign &V) {
    177     Locs.push_back(V);
    178   }
    179 
    180   LLVMContext &getContext() const { return Context; }
    181   const TargetMachine &getTarget() const { return TM; }
    182   MachineFunction &getMachineFunction() const { return MF; }
    183   CallingConv::ID getCallingConv() const { return CallingConv; }
    184   bool isVarArg() const { return IsVarArg; }
    185 
    186   unsigned getNextStackOffset() const { return StackOffset; }
    187 
    188   /// isAllocated - Return true if the specified register (or an alias) is
    189   /// allocated.
    190   bool isAllocated(unsigned Reg) const {
    191     return UsedRegs[Reg/32] & (1 << (Reg&31));
    192   }
    193 
    194   /// AnalyzeFormalArguments - Analyze an array of argument values,
    195   /// incorporating info about the formals into this state.
    196   void AnalyzeFormalArguments(const SmallVectorImpl<ISD::InputArg> &Ins,
    197                               CCAssignFn Fn);
    198 
    199   /// AnalyzeReturn - Analyze the returned values of a return,
    200   /// incorporating info about the result values into this state.
    201   void AnalyzeReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
    202                      CCAssignFn Fn);
    203 
    204   /// CheckReturn - Analyze the return values of a function, returning
    205   /// true if the return can be performed without sret-demotion, and
    206   /// false otherwise.
    207   bool CheckReturn(const SmallVectorImpl<ISD::OutputArg> &ArgsFlags,
    208                    CCAssignFn Fn);
    209 
    210   /// AnalyzeCallOperands - Analyze the outgoing arguments to a call,
    211   /// incorporating info about the passed values into this state.
    212   void AnalyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
    213                            CCAssignFn Fn);
    214 
    215   /// AnalyzeCallOperands - Same as above except it takes vectors of types
    216   /// and argument flags.
    217   void AnalyzeCallOperands(SmallVectorImpl<MVT> &ArgVTs,
    218                            SmallVectorImpl<ISD::ArgFlagsTy> &Flags,
    219                            CCAssignFn Fn);
    220 
    221   /// AnalyzeCallResult - Analyze the return values of a call,
    222   /// incorporating info about the passed values into this state.
    223   void AnalyzeCallResult(const SmallVectorImpl<ISD::InputArg> &Ins,
    224                          CCAssignFn Fn);
    225 
    226   /// AnalyzeCallResult - Same as above except it's specialized for calls which
    227   /// produce a single value.
    228   void AnalyzeCallResult(MVT VT, CCAssignFn Fn);
    229 
    230   /// getFirstUnallocated - Return the first unallocated register in the set, or
    231   /// NumRegs if they are all allocated.
    232   unsigned getFirstUnallocated(const unsigned *Regs, unsigned NumRegs) const {
    233     for (unsigned i = 0; i != NumRegs; ++i)
    234       if (!isAllocated(Regs[i]))
    235         return i;
    236     return NumRegs;
    237   }
    238 
    239   /// AllocateReg - Attempt to allocate one register.  If it is not available,
    240   /// return zero.  Otherwise, return the register, marking it and any aliases
    241   /// as allocated.
    242   unsigned AllocateReg(unsigned Reg) {
    243     if (isAllocated(Reg)) return 0;
    244     MarkAllocated(Reg);
    245     return Reg;
    246   }
    247 
    248   /// Version of AllocateReg with extra register to be shadowed.
    249   unsigned AllocateReg(unsigned Reg, unsigned ShadowReg) {
    250     if (isAllocated(Reg)) return 0;
    251     MarkAllocated(Reg);
    252     MarkAllocated(ShadowReg);
    253     return Reg;
    254   }
    255 
    256   /// AllocateReg - Attempt to allocate one of the specified registers.  If none
    257   /// are available, return zero.  Otherwise, return the first one available,
    258   /// marking it and any aliases as allocated.
    259   unsigned AllocateReg(const unsigned *Regs, unsigned NumRegs) {
    260     unsigned FirstUnalloc = getFirstUnallocated(Regs, NumRegs);
    261     if (FirstUnalloc == NumRegs)
    262       return 0;    // Didn't find the reg.
    263 
    264     // Mark the register and any aliases as allocated.
    265     unsigned Reg = Regs[FirstUnalloc];
    266     MarkAllocated(Reg);
    267     return Reg;
    268   }
    269 
    270   /// Version of AllocateReg with list of registers to be shadowed.
    271   unsigned AllocateReg(const unsigned *Regs, const unsigned *ShadowRegs,
    272                        unsigned NumRegs) {
    273     unsigned FirstUnalloc = getFirstUnallocated(Regs, NumRegs);
    274     if (FirstUnalloc == NumRegs)
    275       return 0;    // Didn't find the reg.
    276 
    277     // Mark the register and any aliases as allocated.
    278     unsigned Reg = Regs[FirstUnalloc], ShadowReg = ShadowRegs[FirstUnalloc];
    279     MarkAllocated(Reg);
    280     MarkAllocated(ShadowReg);
    281     return Reg;
    282   }
    283 
    284   /// AllocateStack - Allocate a chunk of stack space with the specified size
    285   /// and alignment.
    286   unsigned AllocateStack(unsigned Size, unsigned Align) {
    287     assert(Align && ((Align-1) & Align) == 0); // Align is power of 2.
    288     StackOffset = ((StackOffset + Align-1) & ~(Align-1));
    289     unsigned Result = StackOffset;
    290     StackOffset += Size;
    291     return Result;
    292   }
    293 
    294   /// Version of AllocateStack with extra register to be shadowed.
    295   unsigned AllocateStack(unsigned Size, unsigned Align, unsigned ShadowReg) {
    296     MarkAllocated(ShadowReg);
    297     return AllocateStack(Size, Align);
    298   }
    299 
    300   // HandleByVal - Allocate a stack slot large enough to pass an argument by
    301   // value. The size and alignment information of the argument is encoded in its
    302   // parameter attribute.
    303   void HandleByVal(unsigned ValNo, MVT ValVT,
    304                    MVT LocVT, CCValAssign::LocInfo LocInfo,
    305                    int MinSize, int MinAlign, ISD::ArgFlagsTy ArgFlags);
    306 
    307   // First GPR that carries part of a byval aggregate that's split
    308   // between registers and memory.
    309   unsigned getFirstByValReg() { return FirstByValRegValid ? FirstByValReg : 0; }
    310   void setFirstByValReg(unsigned r) { FirstByValReg = r; FirstByValRegValid = true; }
    311   void clearFirstByValReg() { FirstByValReg = 0; FirstByValRegValid = false; }
    312   bool isFirstByValRegValid() { return FirstByValRegValid; }
    313 
    314   ParmContext getCallOrPrologue() { return CallOrPrologue; }
    315 
    316 private:
    317   /// MarkAllocated - Mark a register and all of its aliases as allocated.
    318   void MarkAllocated(unsigned Reg);
    319 };
    320 
    321 
    322 
    323 } // end namespace llvm
    324 
    325 #endif
    326