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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/MachineFrameInfo.h"
     20 #include "llvm/CodeGen/MachineFunction.h"
     21 #include "llvm/CodeGen/ValueTypes.h"
     22 #include "llvm/IR/CallingConv.h"
     23 #include "llvm/Target/TargetCallingConv.h"
     24 
     25 namespace llvm {
     26   class TargetRegisterInfo;
     27   class TargetMachine;
     28   class CCState;
     29 
     30 /// CCValAssign - Represent assignment of one arg/retval to a location.
     31 class CCValAssign {
     32 public:
     33   enum LocInfo {
     34     Full,   // The value fills the full location.
     35     SExt,   // The value is sign extended in the location.
     36     ZExt,   // The value is zero extended in the location.
     37     AExt,   // The value is extended with undefined upper bits.
     38     BCvt,   // The value is bit-converted in the location.
     39     VExt,   // The value is vector-widened in the location.
     40             // FIXME: Not implemented yet. Code that uses AExt to mean
     41             // vector-widen should be fixed to use VExt instead.
     42     Indirect // The location contains pointer to the value.
     43     // TODO: a subset of the value is in the location.
     44   };
     45 private:
     46   /// ValNo - This is the value number begin assigned (e.g. an argument number).
     47   unsigned ValNo;
     48 
     49   /// Loc is either a stack offset or a register number.
     50   unsigned Loc;
     51 
     52   /// isMem - True if this is a memory loc, false if it is a register loc.
     53   unsigned isMem : 1;
     54 
     55   /// isCustom - True if this arg/retval requires special handling.
     56   unsigned isCustom : 1;
     57 
     58   /// Information about how the value is assigned.
     59   LocInfo HTP : 6;
     60 
     61   /// ValVT - The type of the value being assigned.
     62   MVT ValVT;
     63 
     64   /// LocVT - The type of the location being assigned to.
     65   MVT LocVT;
     66 public:
     67 
     68   static CCValAssign getReg(unsigned ValNo, MVT ValVT,
     69                             unsigned RegNo, MVT LocVT,
     70                             LocInfo HTP) {
     71     CCValAssign Ret;
     72     Ret.ValNo = ValNo;
     73     Ret.Loc = RegNo;
     74     Ret.isMem = false;
     75     Ret.isCustom = false;
     76     Ret.HTP = HTP;
     77     Ret.ValVT = ValVT;
     78     Ret.LocVT = LocVT;
     79     return Ret;
     80   }
     81 
     82   static CCValAssign getCustomReg(unsigned ValNo, MVT ValVT,
     83                                   unsigned RegNo, MVT LocVT,
     84                                   LocInfo HTP) {
     85     CCValAssign Ret;
     86     Ret = getReg(ValNo, ValVT, RegNo, LocVT, HTP);
     87     Ret.isCustom = true;
     88     return Ret;
     89   }
     90 
     91   static CCValAssign getMem(unsigned ValNo, MVT ValVT,
     92                             unsigned Offset, MVT LocVT,
     93                             LocInfo HTP) {
     94     CCValAssign Ret;
     95     Ret.ValNo = ValNo;
     96     Ret.Loc = Offset;
     97     Ret.isMem = true;
     98     Ret.isCustom = false;
     99     Ret.HTP = HTP;
    100     Ret.ValVT = ValVT;
    101     Ret.LocVT = LocVT;
    102     return Ret;
    103   }
    104 
    105   static CCValAssign getCustomMem(unsigned ValNo, MVT ValVT,
    106                                   unsigned Offset, MVT LocVT,
    107                                   LocInfo HTP) {
    108     CCValAssign Ret;
    109     Ret = getMem(ValNo, ValVT, Offset, LocVT, HTP);
    110     Ret.isCustom = true;
    111     return Ret;
    112   }
    113 
    114   unsigned getValNo() const { return ValNo; }
    115   MVT getValVT() const { return ValVT; }
    116 
    117   bool isRegLoc() const { return !isMem; }
    118   bool isMemLoc() const { return isMem; }
    119 
    120   bool needsCustom() const { return isCustom; }
    121 
    122   unsigned getLocReg() const { assert(isRegLoc()); return Loc; }
    123   unsigned getLocMemOffset() const { assert(isMemLoc()); return Loc; }
    124   MVT getLocVT() const { return LocVT; }
    125 
    126   LocInfo getLocInfo() const { return HTP; }
    127   bool isExtInLoc() const {
    128     return (HTP == AExt || HTP == SExt || HTP == ZExt);
    129   }
    130 
    131 };
    132 
    133 /// CCAssignFn - This function assigns a location for Val, updating State to
    134 /// reflect the change.  It returns 'true' if it failed to handle Val.
    135 typedef bool CCAssignFn(unsigned ValNo, MVT ValVT,
    136                         MVT LocVT, CCValAssign::LocInfo LocInfo,
    137                         ISD::ArgFlagsTy ArgFlags, CCState &State);
    138 
    139 /// CCCustomFn - This function assigns a location for Val, possibly updating
    140 /// all args to reflect changes and indicates if it handled it. It must set
    141 /// isCustom if it handles the arg and returns true.
    142 typedef bool CCCustomFn(unsigned &ValNo, MVT &ValVT,
    143                         MVT &LocVT, CCValAssign::LocInfo &LocInfo,
    144                         ISD::ArgFlagsTy &ArgFlags, CCState &State);
    145 
    146 /// ParmContext - This enum tracks whether calling convention lowering is in
    147 /// the context of prologue or call generation. Not all backends make use of
    148 /// this information.
    149 typedef enum { Unknown, Prologue, Call } ParmContext;
    150 
    151 /// CCState - This class holds information needed while lowering arguments and
    152 /// return values.  It captures which registers are already assigned and which
    153 /// stack slots are used.  It provides accessors to allocate these values.
    154 class CCState {
    155 private:
    156   CallingConv::ID CallingConv;
    157   bool IsVarArg;
    158   MachineFunction &MF;
    159   const TargetMachine &TM;
    160   const TargetRegisterInfo &TRI;
    161   SmallVectorImpl<CCValAssign> &Locs;
    162   LLVMContext &Context;
    163 
    164   unsigned StackOffset;
    165   SmallVector<uint32_t, 16> UsedRegs;
    166 
    167   // ByValInfo and SmallVector<ByValInfo, 4> ByValRegs:
    168   //
    169   // Vector of ByValInfo instances (ByValRegs) is introduced for byval registers
    170   // tracking.
    171   // Or, in another words it tracks byval parameters that are stored in
    172   // general purpose registers.
    173   //
    174   // For 4 byte stack alignment,
    175   // instance index means byval parameter number in formal
    176   // arguments set. Assume, we have some "struct_type" with size = 4 bytes,
    177   // then, for function "foo":
    178   //
    179   // i32 foo(i32 %p, %struct_type* %r, i32 %s, %struct_type* %t)
    180   //
    181   // ByValRegs[0] describes how "%r" is stored (Begin == r1, End == r2)
    182   // ByValRegs[1] describes how "%t" is stored (Begin == r3, End == r4).
    183   //
    184   // In case of 8 bytes stack alignment,
    185   // ByValRegs may also contain information about wasted registers.
    186   // In function shown above, r3 would be wasted according to AAPCS rules.
    187   // And in that case ByValRegs[1].Waste would be "true".
    188   // ByValRegs vector size still would be 2,
    189   // while "%t" goes to the stack: it wouldn't be described in ByValRegs.
    190   //
    191   // Supposed use-case for this collection:
    192   // 1. Initially ByValRegs is empty, InRegsParamsProceed is 0.
    193   // 2. HandleByVal fillups ByValRegs.
    194   // 3. Argument analysis (LowerFormatArguments, for example). After
    195   // some byval argument was analyzed, InRegsParamsProceed is increased.
    196   struct ByValInfo {
    197     ByValInfo(unsigned B, unsigned E, bool IsWaste = false) :
    198       Begin(B), End(E), Waste(IsWaste) {}
    199     // First register allocated for current parameter.
    200     unsigned Begin;
    201 
    202     // First after last register allocated for current parameter.
    203     unsigned End;
    204 
    205     // Means that current range of registers doesn't belong to any
    206     // parameters. It was wasted due to stack alignment rules.
    207     // For more information see:
    208     // AAPCS, 5.5 Parameter Passing, Stage C, C.3.
    209     bool Waste;
    210   };
    211   SmallVector<ByValInfo, 4 > ByValRegs;
    212 
    213   // InRegsParamsProceed - shows how many instances of ByValRegs was proceed
    214   // during argument analysis.
    215   unsigned InRegsParamsProceed;
    216 
    217 protected:
    218   ParmContext CallOrPrologue;
    219 
    220 public:
    221   CCState(CallingConv::ID CC, bool isVarArg, MachineFunction &MF,
    222           const TargetMachine &TM, SmallVectorImpl<CCValAssign> &locs,
    223           LLVMContext &C);
    224 
    225   void addLoc(const CCValAssign &V) {
    226     Locs.push_back(V);
    227   }
    228 
    229   LLVMContext &getContext() const { return Context; }
    230   const TargetMachine &getTarget() const { return TM; }
    231   MachineFunction &getMachineFunction() const { return MF; }
    232   CallingConv::ID getCallingConv() const { return CallingConv; }
    233   bool isVarArg() const { return IsVarArg; }
    234 
    235   unsigned getNextStackOffset() const { return StackOffset; }
    236 
    237   /// isAllocated - Return true if the specified register (or an alias) is
    238   /// allocated.
    239   bool isAllocated(unsigned Reg) const {
    240     return UsedRegs[Reg/32] & (1 << (Reg&31));
    241   }
    242 
    243   /// AnalyzeFormalArguments - Analyze an array of argument values,
    244   /// incorporating info about the formals into this state.
    245   void AnalyzeFormalArguments(const SmallVectorImpl<ISD::InputArg> &Ins,
    246                               CCAssignFn Fn);
    247 
    248   /// AnalyzeReturn - Analyze the returned values of a return,
    249   /// incorporating info about the result values into this state.
    250   void AnalyzeReturn(const SmallVectorImpl<ISD::OutputArg> &Outs,
    251                      CCAssignFn Fn);
    252 
    253   /// CheckReturn - Analyze the return values of a function, returning
    254   /// true if the return can be performed without sret-demotion, and
    255   /// false otherwise.
    256   bool CheckReturn(const SmallVectorImpl<ISD::OutputArg> &ArgsFlags,
    257                    CCAssignFn Fn);
    258 
    259   /// AnalyzeCallOperands - Analyze the outgoing arguments to a call,
    260   /// incorporating info about the passed values into this state.
    261   void AnalyzeCallOperands(const SmallVectorImpl<ISD::OutputArg> &Outs,
    262                            CCAssignFn Fn);
    263 
    264   /// AnalyzeCallOperands - Same as above except it takes vectors of types
    265   /// and argument flags.
    266   void AnalyzeCallOperands(SmallVectorImpl<MVT> &ArgVTs,
    267                            SmallVectorImpl<ISD::ArgFlagsTy> &Flags,
    268                            CCAssignFn Fn);
    269 
    270   /// AnalyzeCallResult - Analyze the return values of a call,
    271   /// incorporating info about the passed values into this state.
    272   void AnalyzeCallResult(const SmallVectorImpl<ISD::InputArg> &Ins,
    273                          CCAssignFn Fn);
    274 
    275   /// AnalyzeCallResult - Same as above except it's specialized for calls which
    276   /// produce a single value.
    277   void AnalyzeCallResult(MVT VT, CCAssignFn Fn);
    278 
    279   /// getFirstUnallocated - Return the first unallocated register in the set, or
    280   /// NumRegs if they are all allocated.
    281   unsigned getFirstUnallocated(const uint16_t *Regs, unsigned NumRegs) const {
    282     for (unsigned i = 0; i != NumRegs; ++i)
    283       if (!isAllocated(Regs[i]))
    284         return i;
    285     return NumRegs;
    286   }
    287 
    288   /// AllocateReg - Attempt to allocate one register.  If it is not available,
    289   /// return zero.  Otherwise, return the register, marking it and any aliases
    290   /// as allocated.
    291   unsigned AllocateReg(unsigned Reg) {
    292     if (isAllocated(Reg)) return 0;
    293     MarkAllocated(Reg);
    294     return Reg;
    295   }
    296 
    297   /// Version of AllocateReg with extra register to be shadowed.
    298   unsigned AllocateReg(unsigned Reg, unsigned ShadowReg) {
    299     if (isAllocated(Reg)) return 0;
    300     MarkAllocated(Reg);
    301     MarkAllocated(ShadowReg);
    302     return Reg;
    303   }
    304 
    305   /// AllocateReg - Attempt to allocate one of the specified registers.  If none
    306   /// are available, return zero.  Otherwise, return the first one available,
    307   /// marking it and any aliases as allocated.
    308   unsigned AllocateReg(const uint16_t *Regs, unsigned NumRegs) {
    309     unsigned FirstUnalloc = getFirstUnallocated(Regs, NumRegs);
    310     if (FirstUnalloc == NumRegs)
    311       return 0;    // Didn't find the reg.
    312 
    313     // Mark the register and any aliases as allocated.
    314     unsigned Reg = Regs[FirstUnalloc];
    315     MarkAllocated(Reg);
    316     return Reg;
    317   }
    318 
    319   /// Version of AllocateReg with list of registers to be shadowed.
    320   unsigned AllocateReg(const uint16_t *Regs, const uint16_t *ShadowRegs,
    321                        unsigned NumRegs) {
    322     unsigned FirstUnalloc = getFirstUnallocated(Regs, NumRegs);
    323     if (FirstUnalloc == NumRegs)
    324       return 0;    // Didn't find the reg.
    325 
    326     // Mark the register and any aliases as allocated.
    327     unsigned Reg = Regs[FirstUnalloc], ShadowReg = ShadowRegs[FirstUnalloc];
    328     MarkAllocated(Reg);
    329     MarkAllocated(ShadowReg);
    330     return Reg;
    331   }
    332 
    333   /// AllocateStack - Allocate a chunk of stack space with the specified size
    334   /// and alignment.
    335   unsigned AllocateStack(unsigned Size, unsigned Align) {
    336     assert(Align && ((Align-1) & Align) == 0); // Align is power of 2.
    337     StackOffset = ((StackOffset + Align-1) & ~(Align-1));
    338     unsigned Result = StackOffset;
    339     StackOffset += Size;
    340     MF.getFrameInfo()->ensureMaxAlignment(Align);
    341     return Result;
    342   }
    343 
    344   /// Version of AllocateStack with extra register to be shadowed.
    345   unsigned AllocateStack(unsigned Size, unsigned Align, unsigned ShadowReg) {
    346     MarkAllocated(ShadowReg);
    347     return AllocateStack(Size, Align);
    348   }
    349 
    350   // HandleByVal - Allocate a stack slot large enough to pass an argument by
    351   // value. The size and alignment information of the argument is encoded in its
    352   // parameter attribute.
    353   void HandleByVal(unsigned ValNo, MVT ValVT,
    354                    MVT LocVT, CCValAssign::LocInfo LocInfo,
    355                    int MinSize, int MinAlign, ISD::ArgFlagsTy ArgFlags);
    356 
    357   // Returns count of byval arguments that are to be stored (even partly)
    358   // in registers.
    359   unsigned getInRegsParamsCount() const { return ByValRegs.size(); }
    360 
    361   // Returns count of byval in-regs arguments proceed.
    362   unsigned getInRegsParamsProceed() const { return InRegsParamsProceed; }
    363 
    364   // Get information about N-th byval parameter that is stored in registers.
    365   // Here "ByValParamIndex" is N.
    366   void getInRegsParamInfo(unsigned InRegsParamRecordIndex,
    367                           unsigned& BeginReg, unsigned& EndReg) const {
    368     assert(InRegsParamRecordIndex < ByValRegs.size() &&
    369            "Wrong ByVal parameter index");
    370 
    371     const ByValInfo& info = ByValRegs[InRegsParamRecordIndex];
    372     BeginReg = info.Begin;
    373     EndReg = info.End;
    374   }
    375 
    376   // Add information about parameter that is kept in registers.
    377   void addInRegsParamInfo(unsigned RegBegin, unsigned RegEnd) {
    378     ByValRegs.push_back(ByValInfo(RegBegin, RegEnd));
    379   }
    380 
    381   // Goes either to next byval parameter (excluding "waste" record), or
    382   // to the end of collection.
    383   // Returns false, if end is reached.
    384   bool nextInRegsParam() {
    385     unsigned e = ByValRegs.size();
    386     if (InRegsParamsProceed < e)
    387       ++InRegsParamsProceed;
    388     return InRegsParamsProceed < e;
    389   }
    390 
    391   // Clear byval registers tracking info.
    392   void clearByValRegsInfo() {
    393     InRegsParamsProceed = 0;
    394     ByValRegs.clear();
    395   }
    396 
    397   ParmContext getCallOrPrologue() const { return CallOrPrologue; }
    398 
    399 private:
    400   /// MarkAllocated - Mark a register and all of its aliases as allocated.
    401   void MarkAllocated(unsigned Reg);
    402 };
    403 
    404 
    405 
    406 } // end namespace llvm
    407 
    408 #endif
    409