BPFISelLowering.h
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//===-- BPFISelLowering.h - BPF DAG Lowering Interface ----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the interfaces that BPF uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_TARGET_BPF_BPFISELLOWERING_H
#define LLVM_LIB_TARGET_BPF_BPFISELLOWERING_H
#include "BPF.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/TargetLowering.h"
namespace llvm {
class BPFSubtarget;
namespace BPFISD {
enum NodeType : unsigned {
FIRST_NUMBER = ISD::BUILTIN_OP_END,
RET_FLAG,
CALL,
SELECT_CC,
BR_CC,
Wrapper,
MEMCPY
};
}
class BPFTargetLowering : public TargetLowering {
public:
explicit BPFTargetLowering(const TargetMachine &TM, const BPFSubtarget &STI);
// Provide custom lowering hooks for some operations.
SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
// This method returns the name of a target specific DAG node.
const char *getTargetNodeName(unsigned Opcode) const override;
// This method decides whether folding a constant offset
// with the given GlobalAddress is legal.
bool isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const override;
std::pair<unsigned, const TargetRegisterClass *>
getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
StringRef Constraint, MVT VT) const override;
MachineBasicBlock *
EmitInstrWithCustomInserter(MachineInstr &MI,
MachineBasicBlock *BB) const override;
bool getHasAlu32() const { return HasAlu32; }
bool getHasJmp32() const { return HasJmp32; }
bool getHasJmpExt() const { return HasJmpExt; }
EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Context,
EVT VT) const override;
MVT getScalarShiftAmountTy(const DataLayout &, EVT) const override;
private:
// Control Instruction Selection Features
bool HasAlu32;
bool HasJmp32;
bool HasJmpExt;
SDValue LowerBR_CC(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const;
SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
// Lower the result values of a call, copying them out of physregs into vregs
SDValue LowerCallResult(SDValue Chain, SDValue InFlag,
CallingConv::ID CallConv, bool IsVarArg,
const SmallVectorImpl<ISD::InputArg> &Ins,
const SDLoc &DL, SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals) const;
// Maximum number of arguments to a call
static const unsigned MaxArgs;
// Lower a call into CALLSEQ_START - BPFISD:CALL - CALLSEQ_END chain
SDValue LowerCall(TargetLowering::CallLoweringInfo &CLI,
SmallVectorImpl<SDValue> &InVals) const override;
// Lower incoming arguments, copy physregs into vregs
SDValue LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv,
bool IsVarArg,
const SmallVectorImpl<ISD::InputArg> &Ins,
const SDLoc &DL, SelectionDAG &DAG,
SmallVectorImpl<SDValue> &InVals) const override;
SDValue LowerReturn(SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
const SmallVectorImpl<ISD::OutputArg> &Outs,
const SmallVectorImpl<SDValue> &OutVals, const SDLoc &DL,
SelectionDAG &DAG) const override;
EVT getOptimalMemOpType(const MemOp &Op,
const AttributeList &FuncAttributes) const override {
return Op.size() >= 8 ? MVT::i64 : MVT::i32;
}
bool shouldConvertConstantLoadToIntImm(const APInt &Imm,
Type *Ty) const override {
return true;
}
// Prevent reducing load width during SelectionDag phase.
// Otherwise, we may transform the following
// ctx = ctx + reloc_offset
// ... (*(u32 *)ctx) & 0x8000...
// to
// ctx = ctx + reloc_offset
// ... (*(u8 *)(ctx + 1)) & 0x80 ...
// which will be rejected by the verifier.
bool shouldReduceLoadWidth(SDNode *Load, ISD::LoadExtType ExtTy,
EVT NewVT) const override {
return false;
}
// isTruncateFree - Return true if it's free to truncate a value of
// type Ty1 to type Ty2. e.g. On BPF at alu32 mode, it's free to truncate
// a i64 value in register R1 to i32 by referencing its sub-register W1.
bool isTruncateFree(Type *Ty1, Type *Ty2) const override;
bool isTruncateFree(EVT VT1, EVT VT2) const override;
// For 32bit ALU result zext to 64bit is free.
bool isZExtFree(Type *Ty1, Type *Ty2) const override;
bool isZExtFree(EVT VT1, EVT VT2) const override;
unsigned EmitSubregExt(MachineInstr &MI, MachineBasicBlock *BB, unsigned Reg,
bool isSigned) const;
MachineBasicBlock * EmitInstrWithCustomInserterMemcpy(MachineInstr &MI,
MachineBasicBlock *BB)
const;
};
}
#endif