include/llvm/CodeGen/GlobalISel/CallLowering.h

   1 //===- llvm/CodeGen/GlobalISel/CallLowering.h - Call lowering ---*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 ///
   9 /// \file
  10 /// This file describes how to lower LLVM calls to machine code calls.
  11 ///
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_CODEGEN_GLOBALISEL_CALLLOWERING_H
  15 #define LLVM_CODEGEN_GLOBALISEL_CALLLOWERING_H
  16
  17 #include "llvm/ADT/ArrayRef.h"
  18 #include "llvm/ADT/SmallVector.h"
  19 #include "llvm/CodeGen/CallingConvLower.h"
  20 #include "llvm/CodeGen/TargetCallingConv.h"
  21 #include "llvm/IR/CallSite.h"
  22 #include "llvm/IR/CallingConv.h"
  23 #include "llvm/Support/ErrorHandling.h"
  24 #include "llvm/Support/MachineValueType.h"
  25 #include <cstdint>
  26 #include <functional>
  27
  28 namespace llvm {
  29
  30 class DataLayout;
  31 class Function;
  32 class MachineIRBuilder;
  33 class MachineOperand;
  34 struct MachinePointerInfo;
  35 class MachineRegisterInfo;
  36 class TargetLowering;
  37 class Type;
  38 class Value;
  39
  40 class CallLowering {
  41   const TargetLowering *TLI;
  42
  43   virtual void anchor();
  44 public:
  45   struct ArgInfo {
  46     SmallVector<Register, 4> Regs;
  47     Type *Ty;
  48     ISD::ArgFlagsTy Flags;
  49     bool IsFixed;
  50
  51     ArgInfo(ArrayRef<Register> Regs, Type *Ty,
  52             ISD::ArgFlagsTy Flags = ISD::ArgFlagsTy{}, bool IsFixed = true)
  53         : Regs(Regs.begin(), Regs.end()), Ty(Ty), Flags(Flags),
  54           IsFixed(IsFixed) {
  55       // FIXME: We should have just one way of saying "no register".
  56       assert((Ty->isVoidTy() == (Regs.empty() || Regs[0] == 0)) &&
  57              "only void types should have no register");
  58     }
  59   };
  60
  61   /// Argument handling is mostly uniform between the four places that
  62   /// make these decisions: function formal arguments, call
  63   /// instruction args, call instruction returns and function
  64   /// returns. However, once a decision has been made on where an
  65   /// arugment should go, exactly what happens can vary slightly. This
  66   /// class abstracts the differences.
  67   struct ValueHandler {
  68     ValueHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
  69                  CCAssignFn *AssignFn)
  70       : MIRBuilder(MIRBuilder), MRI(MRI), AssignFn(AssignFn) {}
  71
  72     virtual ~ValueHandler() = default;
  73
  74     /// Returns true if the handler is dealing with formal arguments,
  75     /// not with return values etc.
  76     virtual bool isArgumentHandler() const { return false; }
  77
  78     /// Materialize a VReg containing the address of the specified
  79     /// stack-based object. This is either based on a FrameIndex or
  80     /// direct SP manipulation, depending on the context. \p MPO
  81     /// should be initialized to an appropriate description of the
  82     /// address created.
  83     virtual Register getStackAddress(uint64_t Size, int64_t Offset,
  84                                      MachinePointerInfo &MPO) = 0;
  85
  86     /// The specified value has been assigned to a physical register,
  87     /// handle the appropriate COPY (either to or from) and mark any
  88     /// relevant uses/defines as needed.
  89     virtual void assignValueToReg(Register ValVReg, Register PhysReg,
  90                                   CCValAssign &VA) = 0;
  91
  92     /// The specified value has been assigned to a stack
  93     /// location. Load or store it there, with appropriate extension
  94     /// if necessary.
  95     virtual void assignValueToAddress(Register ValVReg, Register Addr,
  96                                       uint64_t Size, MachinePointerInfo &MPO,
  97                                       CCValAssign &VA) = 0;
  98
  99     /// Handle custom values, which may be passed into one or more of \p VAs.
 100     /// \return The number of \p VAs that have been assigned after the first
 101     ///         one, and which should therefore be skipped from further
 102     ///         processing.
 103     virtual unsigned assignCustomValue(const ArgInfo &Arg,
 104                                        ArrayRef<CCValAssign> VAs) {
 105       // This is not a pure virtual method because not all targets need to worry
 106       // about custom values.
 107       llvm_unreachable("Custom values not supported");
 108     }
 109
 110     Register extendRegister(Register ValReg, CCValAssign &VA);
 111
 112     virtual bool assignArg(unsigned ValNo, MVT ValVT, MVT LocVT,
 113                            CCValAssign::LocInfo LocInfo, const ArgInfo &Info,
 114                            CCState &State) {
 115       return AssignFn(ValNo, ValVT, LocVT, LocInfo, Info.Flags, State);
 116     }
 117
 118     MachineIRBuilder &MIRBuilder;
 119     MachineRegisterInfo &MRI;
 120     CCAssignFn *AssignFn;
 121
 122   private:
 123     virtual void anchor();
 124   };
 125
 126 protected:
 127   /// Getter for generic TargetLowering class.
 128   const TargetLowering *getTLI() const {
 129     return TLI;
 130   }
 131
 132   /// Getter for target specific TargetLowering class.
 133   template <class XXXTargetLowering>
 134     const XXXTargetLowering *getTLI() const {
 135     return static_cast<const XXXTargetLowering *>(TLI);
 136   }
 137
 138   template <typename FuncInfoTy>
 139   void setArgFlags(ArgInfo &Arg, unsigned OpIdx, const DataLayout &DL,
 140                    const FuncInfoTy &FuncInfo) const;
 141
 142   /// Generate instructions for packing \p SrcRegs into one big register
 143   /// corresponding to the aggregate type \p PackedTy.
 144   ///
 145   /// \param SrcRegs should contain one virtual register for each base type in
 146   ///                \p PackedTy, as returned by computeValueLLTs.
 147   ///
 148   /// \return The packed register.
 149   Register packRegs(ArrayRef<Register> SrcRegs, Type *PackedTy,
 150                     MachineIRBuilder &MIRBuilder) const;
 151
 152   /// Generate instructions for unpacking \p SrcReg into the \p DstRegs
 153   /// corresponding to the aggregate type \p PackedTy.
 154   ///
 155   /// \param DstRegs should contain one virtual register for each base type in
 156   ///        \p PackedTy, as returned by computeValueLLTs.
 157   void unpackRegs(ArrayRef<Register> DstRegs, Register SrcReg, Type *PackedTy,
 158                   MachineIRBuilder &MIRBuilder) const;
 159
 160   /// Invoke Handler::assignArg on each of the given \p Args and then use
 161   /// \p Callback to move them to the assigned locations.
 162   ///
 163   /// \return True if everything has succeeded, false otherwise.
 164   bool handleAssignments(MachineIRBuilder &MIRBuilder, ArrayRef<ArgInfo> Args,
 165                          ValueHandler &Handler) const;
 166
 167 public:
 168   CallLowering(const TargetLowering *TLI) : TLI(TLI) {}
 169   virtual ~CallLowering() = default;
 170
 171   /// \return true if the target is capable of handling swifterror values that
 172   /// have been promoted to a specified register. The extended versions of
 173   /// lowerReturn and lowerCall should be implemented.
 174   virtual bool supportSwiftError() const {
 175     return false;
 176   }
 177
 178   /// This hook must be implemented to lower outgoing return values, described
 179   /// by \p Val, into the specified virtual registers \p VRegs.
 180   /// This hook is used by GlobalISel.
 181   ///
 182   /// \p SwiftErrorVReg is non-zero if the function has a swifterror parameter
 183   /// that needs to be implicitly returned.
 184   ///
 185   /// \return True if the lowering succeeds, false otherwise.
 186   virtual bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
 187                            ArrayRef<Register> VRegs,
 188                            Register SwiftErrorVReg) const {
 189     if (!supportSwiftError()) {
 190       assert(SwiftErrorVReg == 0 && "attempt to use unsupported swifterror");
 191       return lowerReturn(MIRBuilder, Val, VRegs);
 192     }
 193     return false;
 194   }
 195
 196   /// This hook behaves as the extended lowerReturn function, but for targets
 197   /// that do not support swifterror value promotion.
 198   virtual bool lowerReturn(MachineIRBuilder &MIRBuilder, const Value *Val,
 199                            ArrayRef<Register> VRegs) const {
 200     return false;
 201   }
 202
 203   /// This hook must be implemented to lower the incoming (formal)
 204   /// arguments, described by \p VRegs, for GlobalISel. Each argument
 205   /// must end up in the related virtual registers described by \p VRegs.
 206   /// In other words, the first argument should end up in \c VRegs[0],
 207   /// the second in \c VRegs[1], and so on. For each argument, there will be one
 208   /// register for each non-aggregate type, as returned by \c computeValueLLTs.
 209   /// \p MIRBuilder is set to the proper insertion for the argument
 210   /// lowering.
 211   ///
 212   /// \return True if the lowering succeeded, false otherwise.
 213   virtual bool lowerFormalArguments(MachineIRBuilder &MIRBuilder,
 214                                     const Function &F,
 215                                     ArrayRef<ArrayRef<Register>> VRegs) const {
 216     return false;
 217   }
 218
 219   /// This hook must be implemented to lower the given call instruction,
 220   /// including argument and return value marshalling.
 221   ///
 222   /// \p CallConv is the calling convention to be used for the call.
 223   ///
 224   /// \p Callee is the destination of the call. It should be either a register,
 225   /// globaladdress, or externalsymbol.
 226   ///
 227   /// \p OrigRet is a descriptor for the return type of the function.
 228   ///
 229   /// \p OrigArgs is a list of descriptors of the arguments passed to the
 230   /// function.
 231   ///
 232   /// \p SwiftErrorVReg is non-zero if the call has a swifterror inout
 233   /// parameter, and contains the vreg that the swifterror should be copied into
 234   /// after the call.
 235   ///
 236   /// \return true if the lowering succeeded, false otherwise.
 237   virtual bool lowerCall(MachineIRBuilder &MIRBuilder, CallingConv::ID CallConv,
 238                          const MachineOperand &Callee, const ArgInfo &OrigRet,
 239                          ArrayRef<ArgInfo> OrigArgs,
 240                          Register SwiftErrorVReg) const {
 241     if (!supportSwiftError()) {
 242       assert(SwiftErrorVReg == 0 && "trying to use unsupported swifterror");
 243       return lowerCall(MIRBuilder, CallConv, Callee, OrigRet, OrigArgs);
 244     }
 245     return false;
 246   }
 247
 248   /// This hook behaves as the extended lowerCall function, but for targets that
 249   /// do not support swifterror value promotion.
 250   virtual bool lowerCall(MachineIRBuilder &MIRBuilder, CallingConv::ID CallConv,
 251                          const MachineOperand &Callee, const ArgInfo &OrigRet,
 252                          ArrayRef<ArgInfo> OrigArgs) const {
 253     return false;
 254   }
 255
 256   /// Lower the given call instruction, including argument and return value
 257   /// marshalling.
 258   ///
 259   /// \p CI is the call/invoke instruction.
 260   ///
 261   /// \p ResRegs are the registers where the call's return value should be
 262   /// stored (or 0 if there is no return value). There will be one register for
 263   /// each non-aggregate type, as returned by \c computeValueLLTs.
 264   ///
 265   /// \p ArgRegs is a list of lists of virtual registers containing each
 266   /// argument that needs to be passed (argument \c i should be placed in \c
 267   /// ArgRegs[i]). For each argument, there will be one register for each
 268   /// non-aggregate type, as returned by \c computeValueLLTs.
 269   ///
 270   /// \p SwiftErrorVReg is non-zero if the call has a swifterror inout
 271   /// parameter, and contains the vreg that the swifterror should be copied into
 272   /// after the call.
 273   ///
 274   /// \p GetCalleeReg is a callback to materialize a register for the callee if
 275   /// the target determines it cannot jump to the destination based purely on \p
 276   /// CI. This might be because \p CI is indirect, or because of the limited
 277   /// range of an immediate jump.
 278   ///
 279   /// \return true if the lowering succeeded, false otherwise.
 280   bool lowerCall(MachineIRBuilder &MIRBuilder, ImmutableCallSite CS,
 281                  ArrayRef<Register> ResRegs,
 282                  ArrayRef<ArrayRef<Register>> ArgRegs, Register SwiftErrorVReg,
 283                  std::function<unsigned()> GetCalleeReg) const;
 284 };
 285
 286 } // end namespace llvm
 287
 288 #endif // LLVM_CODEGEN_GLOBALISEL_CALLLOWERING_H