RISCVMatInt.h

//===- RISCVMatInt.h - Immediate materialisation ---------------*- 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_TARGET_RISCV_MCTARGETDESC_MATINT_H
#define LLVM_LIB_TARGET_RISCV_MCTARGETDESC_MATINT_H

#include "llvm/ADT/SmallVector.h"
#include "llvm/MC/MCRegister.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include <cstdint>

namespace llvm {
class APInt;

namespace RISCVMatInt {

enum OpndKind {
  RegImm, // ADDI/ADDIW/SLLI/SRLI/BSETI/BCLRI
  Imm,    // LUI
  RegReg, // SH1ADD/SH2ADD/SH3ADD
  RegX0,  // ADD_UW
};

class Inst {
  unsigned Opc;
  int32_t Imm; // The largest value we need to store is 20 bits.

public:
  Inst(unsigned Opc, int64_t I) : Opc(Opc), Imm(I) {
    assert(I == Imm && "truncated");
  }

  unsigned getOpcode() const { return Opc; }
  int64_t getImm() const { return Imm; }

  OpndKind getOpndKind() const;
};
using InstSeq = SmallVector<Inst, 8>;

// Helper to generate an instruction sequence that will materialise the given
// immediate value into a register. A sequence of instructions represented by a
// simple struct is produced rather than directly emitting the instructions in
// order to allow this helper to be used from both the MC layer and during
// instruction selection.
InstSeq generateInstSeq(int64_t Val, const MCSubtargetInfo &STI);

// Helper to generate the generateInstSeq instruction sequence using MCInsts
void generateMCInstSeq(int64_t Val, const MCSubtargetInfo &STI,
                       MCRegister DestReg, SmallVectorImpl<MCInst> &Insts);

// Helper to generate an instruction sequence that can materialize the given
// immediate value into a register using an additional temporary register. This
// handles cases where the constant can be generated by (ADD (SLLI X, C), X) or
// (ADD_UW (SLLI X, C) X). The sequence to generate X is returned. ShiftAmt is
// provides the SLLI and AddOpc indicates ADD or ADD_UW.
InstSeq generateTwoRegInstSeq(int64_t Val, const MCSubtargetInfo &STI,
                              unsigned &ShiftAmt, unsigned &AddOpc);

// Helper to estimate the number of instructions required to materialise the
// given immediate value into a register. This estimate does not account for
// `Val` possibly fitting into an immediate, and so may over-estimate.
//
// This will attempt to produce instructions to materialise `Val` as an
// `Size`-bit immediate.
//
// If CompressionCost is true it will use a different cost calculation if RVC is
// enabled. This should be used to compare two different sequences to determine
// which is more compressible.
//
// If FreeZeroes is true, it will be assumed free to materialize any
// XLen-sized chunks that are 0. This is appropriate to use in instances when
// the zero register can be used, e.g. when estimating the cost of
// materializing a value used by a particular operation.
int getIntMatCost(const APInt &Val, unsigned Size, const MCSubtargetInfo &STI,
                  bool CompressionCost = false, bool FreeZeroes = false);
} // namespace RISCVMatInt
} // namespace llvm
#endif