SystemZISelLowering.h

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//===-- SystemZISelLowering.h - SystemZ DAG lowering interface --*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the interfaces that SystemZ uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZISELLOWERING_H
#define LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZISELLOWERING_H

#include "SystemZ.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/Target/TargetLowering.h"

namespace llvm {
namespace SystemZISD {
enum {
  FIRST_NUMBER = ISD::BUILTIN_OP_END,

  // Return with a flag operand.  Operand 0 is the chain operand.
  RET_FLAG,

  // Calls a function.  Operand 0 is the chain operand and operand 1
  // is the target address.  The arguments start at operand 2.
  // There is an optional glue operand at the end.
  CALL,
  SIBCALL,

  // Wraps a TargetGlobalAddress that should be loaded using PC-relative
  // accesses (LARL).  Operand 0 is the address.
  PCREL_WRAPPER,

  // Used in cases where an offset is applied to a TargetGlobalAddress.
  // Operand 0 is the full TargetGlobalAddress and operand 1 is a
  // PCREL_WRAPPER for an anchor point.  This is used so that we can
  // cheaply refer to either the full address or the anchor point
  // as a register base.
  PCREL_OFFSET,

  // Integer absolute.
  IABS,

  // Integer comparisons.  There are three operands: the two values
  // to compare, and an integer of type SystemZICMP.
  ICMP,

  // Floating-point comparisons.  The two operands are the values to compare.
  FCMP,

  // Test under mask.  The first operand is ANDed with the second operand
  // and the condition codes are set on the result.  The third operand is
  // a boolean that is true if the condition codes need to distinguish
  // between CCMASK_TM_MIXED_MSB_0 and CCMASK_TM_MIXED_MSB_1 (which the
  // register forms do but the memory forms don't).
  TM,

  // Branches if a condition is true.  Operand 0 is the chain operand;
  // operand 1 is the 4-bit condition-code mask, with bit N in
  // big-endian order meaning "branch if CC=N"; operand 2 is the
  // target block and operand 3 is the flag operand.
  BR_CCMASK,

  // Selects between operand 0 and operand 1.  Operand 2 is the
  // mask of condition-code values for which operand 0 should be
  // chosen over operand 1; it has the same form as BR_CCMASK.
  // Operand 3 is the flag operand.
  SELECT_CCMASK,

  // Evaluates to the gap between the stack pointer and the
  // base of the dynamically-allocatable area.
  ADJDYNALLOC,

  // Extracts the value of a 32-bit access register.  Operand 0 is
  // the number of the register.
  EXTRACT_ACCESS,

  // Wrappers around the ISD opcodes of the same name.  The output and
  // first input operands are GR128s.  The trailing numbers are the
  // widths of the second operand in bits.
  UMUL_LOHI64,
  SDIVREM32,
  SDIVREM64,
  UDIVREM32,
  UDIVREM64,

  // Use a series of MVCs to copy bytes from one memory location to another.
  // The operands are:
  // - the target address
  // - the source address
  // - the constant length
  //
  // This isn't a memory opcode because we'd need to attach two
  // MachineMemOperands rather than one.
  MVC,

  // Like MVC, but implemented as a loop that handles X*256 bytes
  // followed by straight-line code to handle the rest (if any).
  // The value of X is passed as an additional operand.
  MVC_LOOP,

  // Similar to MVC and MVC_LOOP, but for logic operations (AND, OR, XOR).
  NC,
  NC_LOOP,
  OC,
  OC_LOOP,
  XC,
  XC_LOOP,

  // Use CLC to compare two blocks of memory, with the same comments
  // as for MVC and MVC_LOOP.
  CLC,
  CLC_LOOP,

  // Use an MVST-based sequence to implement stpcpy().
  STPCPY,

  // Use a CLST-based sequence to implement strcmp().  The two input operands
  // are the addresses of the strings to compare.
  STRCMP,

  // Use an SRST-based sequence to search a block of memory.  The first
  // operand is the end address, the second is the start, and the third
  // is the character to search for.  CC is set to 1 on success and 2
  // on failure.
  SEARCH_STRING,

  // Store the CC value in bits 29 and 28 of an integer.
  IPM,

  // Perform a serialization operation.  (BCR 15,0 or BCR 14,0.)
  SERIALIZE,

  // Wrappers around the inner loop of an 8- or 16-bit ATOMIC_SWAP or
  // ATOMIC_LOAD_<op>.
  //
  // Operand 0: the address of the containing 32-bit-aligned field
  // Operand 1: the second operand of <op>, in the high bits of an i32
  //            for everything except ATOMIC_SWAPW
  // Operand 2: how many bits to rotate the i32 left to bring the first
  //            operand into the high bits
  // Operand 3: the negative of operand 2, for rotating the other way
  // Operand 4: the width of the field in bits (8 or 16)
  ATOMIC_SWAPW = ISD::FIRST_TARGET_MEMORY_OPCODE,
  ATOMIC_LOADW_ADD,
  ATOMIC_LOADW_SUB,
  ATOMIC_LOADW_AND,
  ATOMIC_LOADW_OR,
  ATOMIC_LOADW_XOR,
  ATOMIC_LOADW_NAND,
  ATOMIC_LOADW_MIN,
  ATOMIC_LOADW_MAX,
  ATOMIC_LOADW_UMIN,
  ATOMIC_LOADW_UMAX,

  // A wrapper around the inner loop of an ATOMIC_CMP_SWAP.
  //
  // Operand 0: the address of the containing 32-bit-aligned field
  // Operand 1: the compare value, in the low bits of an i32
  // Operand 2: the swap value, in the low bits of an i32
  // Operand 3: how many bits to rotate the i32 left to bring the first
  //            operand into the high bits
  // Operand 4: the negative of operand 2, for rotating the other way
  // Operand 5: the width of the field in bits (8 or 16)
  ATOMIC_CMP_SWAPW,

  // Prefetch from the second operand using the 4-bit control code in
  // the first operand.  The code is 1 for a load prefetch and 2 for
  // a store prefetch.
  PREFETCH
};

// Return true if OPCODE is some kind of PC-relative address.
inline bool isPCREL(unsigned Opcode) {
  return Opcode == PCREL_WRAPPER || Opcode == PCREL_OFFSET;
}
} // end namespace SystemZISD

namespace SystemZICMP {
// Describes whether an integer comparison needs to be signed or unsigned,
// or whether either type is OK.
enum {
  Any,
  UnsignedOnly,
  SignedOnly
};
} // end namespace SystemZICMP

class SystemZSubtarget;
class SystemZTargetMachine;

class SystemZTargetLowering : public TargetLowering {
public:
  explicit SystemZTargetLowering(const TargetMachine &TM);

  // Override TargetLowering.
  MVT getScalarShiftAmountTy(EVT LHSTy) const override {
    return MVT::i32;
  }
  EVT getSetCCResultType(LLVMContext &, EVT) const override;
  bool isFMAFasterThanFMulAndFAdd(EVT VT) const override;
  bool isFPImmLegal(const APFloat &Imm, EVT VT) const override;
  bool isLegalAddressingMode(const AddrMode &AM, Type *Ty) const override;
  bool allowsMisalignedMemoryAccesses(EVT VT, unsigned AS,
                                      unsigned Align,
                                      bool *Fast) const override;
  bool isTruncateFree(Type *, Type *) const override;
  bool isTruncateFree(EVT, EVT) const override;
  const char *getTargetNodeName(unsigned Opcode) const override;
  std::pair<unsigned, const TargetRegisterClass *>
    getRegForInlineAsmConstraint(const std::string &Constraint,
                                 MVT VT) const override;
  TargetLowering::ConstraintType
    getConstraintType(const std::string &Constraint) const override;
  TargetLowering::ConstraintWeight
    getSingleConstraintMatchWeight(AsmOperandInfo &info,
                                   const char *constraint) const override;
  void LowerAsmOperandForConstraint(SDValue Op,
                                    std::string &Constraint,
                                    std::vector<SDValue> &Ops,
                                    SelectionDAG &DAG) const override;
  MachineBasicBlock *EmitInstrWithCustomInserter(MachineInstr *MI,
                                                 MachineBasicBlock *BB) const
    override;
  SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
  bool allowTruncateForTailCall(Type *, Type *) const override;
  bool mayBeEmittedAsTailCall(CallInst *CI) const override;
  SDValue LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv,
                               bool isVarArg,
                               const SmallVectorImpl<ISD::InputArg> &Ins,
                               SDLoc DL, SelectionDAG &DAG,
                               SmallVectorImpl<SDValue> &InVals) const override;
  SDValue LowerCall(CallLoweringInfo &CLI,
                    SmallVectorImpl<SDValue> &InVals) const override;

  SDValue LowerReturn(SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
                      const SmallVectorImpl<ISD::OutputArg> &Outs,
                      const SmallVectorImpl<SDValue> &OutVals,
                      SDLoc DL, SelectionDAG &DAG) const override;
  SDValue prepareVolatileOrAtomicLoad(SDValue Chain, SDLoc DL,
                                      SelectionDAG &DAG) const override;
  SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;

private:
  const SystemZSubtarget &Subtarget;

  // Implement LowerOperation for individual opcodes.
  SDValue lowerSETCC(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerBR_CC(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerGlobalAddress(GlobalAddressSDNode *Node,
                             SelectionDAG &DAG) const;
  SDValue lowerGlobalTLSAddress(GlobalAddressSDNode *Node,
                                SelectionDAG &DAG) const;
  SDValue lowerBlockAddress(BlockAddressSDNode *Node,
                            SelectionDAG &DAG) const;
  SDValue lowerJumpTable(JumpTableSDNode *JT, SelectionDAG &DAG) const;
  SDValue lowerConstantPool(ConstantPoolSDNode *CP, SelectionDAG &DAG) const;
  SDValue lowerVASTART(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerVACOPY(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerSMUL_LOHI(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerUMUL_LOHI(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerSDIVREM(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerUDIVREM(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerBITCAST(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerOR(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerATOMIC_LOAD(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerATOMIC_STORE(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerATOMIC_LOAD_OP(SDValue Op, SelectionDAG &DAG,
                              unsigned Opcode) const;
  SDValue lowerATOMIC_LOAD_SUB(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerATOMIC_CMP_SWAP(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerLOAD_SEQUENCE_POINT(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerSTACKSAVE(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerSTACKRESTORE(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerPREFETCH(SDValue Op, SelectionDAG &DAG) const;

  // If the last instruction before MBBI in MBB was some form of COMPARE,
  // try to replace it with a COMPARE AND BRANCH just before MBBI.
  // CCMask and Target are the BRC-like operands for the branch.
  // Return true if the change was made.
  bool convertPrevCompareToBranch(MachineBasicBlock *MBB,
                                  MachineBasicBlock::iterator MBBI,
                                  unsigned CCMask,
                                  MachineBasicBlock *Target) const;

  // Implement EmitInstrWithCustomInserter for individual operation types.
  MachineBasicBlock *emitSelect(MachineInstr *MI,
                                MachineBasicBlock *BB) const;
  MachineBasicBlock *emitCondStore(MachineInstr *MI,
                                   MachineBasicBlock *BB,
                                   unsigned StoreOpcode, unsigned STOCOpcode,
                                   bool Invert) const;
  MachineBasicBlock *emitExt128(MachineInstr *MI,
                                MachineBasicBlock *MBB,
                                bool ClearEven, unsigned SubReg) const;
  MachineBasicBlock *emitAtomicLoadBinary(MachineInstr *MI,
                                          MachineBasicBlock *BB,
                                          unsigned BinOpcode, unsigned BitSize,
                                          bool Invert = false) const;
  MachineBasicBlock *emitAtomicLoadMinMax(MachineInstr *MI,
                                          MachineBasicBlock *MBB,
                                          unsigned CompareOpcode,
                                          unsigned KeepOldMask,
                                          unsigned BitSize) const;
  MachineBasicBlock *emitAtomicCmpSwapW(MachineInstr *MI,
                                        MachineBasicBlock *BB) const;
  MachineBasicBlock *emitMemMemWrapper(MachineInstr *MI,
                                       MachineBasicBlock *BB,
                                       unsigned Opcode) const;
  MachineBasicBlock *emitStringWrapper(MachineInstr *MI,
                                       MachineBasicBlock *BB,
                                       unsigned Opcode) const;
};
} // end namespace llvm

#endif