Class: UdbGen::InstTable::TableBuilder

Inherits:
Object
  • Object
show all
Extended by:
T::Sig
Defined in:
lib/udb-gen/generators/inst_table/table_builder.rb

Instance Method Summary collapse

Constructor Details

#initialize(arch, file_name) ⇒ TableBuilder

Returns a new instance of TableBuilder.



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# File 'lib/udb-gen/generators/inst_table/table_builder.rb', line 18

def initialize(arch, file_name)
  @arch = arch
  @file_name = file_name
end

Instance Method Details

#generate ⇒ Object 



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# File 'lib/udb-gen/generators/inst_table/table_builder.rb', line 61

def generate
  lines = []
  @arch.instructions.each do |inst|
    enc_32 = get_encoding(inst, 32)
    enc_64 = get_encoding(inst, 64)

    if enc_32.empty? && enc_64.empty?
      puts "instruction #{inst.name} not supported by 32-bit or 64-bit"
      next
    end

    # Same encoding for 32/64-bit
    if (enc_32 == enc_64)
      lines << ([inst.name, "common"] + enc_64).join(" ")
      next
    end

    # There are some instructions that have different encodings on 32/64-bit
    unless enc_32.empty? || enc_64.empty?
      lines << ([inst.name, "common,32"] + enc_32).join(" ")
      lines << ([inst.name, "common,64"] + enc_64).join(" ")
      next
    end

    if enc_32.any?
      lines << ([inst.name, "32"] + enc_32).join(" ")
      next
    end

    if enc_64.any?
      lines << ([inst.name, "64"] + enc_64).join(" ")
      next
    end
  end

  command = "./bin/generate inst-table"
  command += " -o #{@file_name}" unless @file_name.nil?

  header = <<EOM
# SPDX-License-Identifier: BSD-3-Clause-Clear
#
# GENERATED WITH https://github.com/riscv-software-src/riscv-unified-db
# "#{command}"
#
# Each line of the instruction table should have the following format:
# NAME BASE FIXED_BITS [VARIABLE_LIST]
# NAME                        instruction name
# BASE                        instruction base size (common[,(32|64)])
#                             "common" means the instruction is valid on both architecture sizes
#                             "32" or "64" means the instruction is valid on that size
#                             if the instruction is valid on both architectures but has unique
#                             encodings, use a 32-bit entry "common,32" and 64-bit entry
# FIXED_BITS                  bitfields of the fixed bits of an instruction concatenated with '|'
#                             continuous grouping of fixed bits are in the form of 'bits<offset'
# VARIABLE_LIST               a variable sized list of all variables in the instruction definition
#                             in the form of name[~][<num][!num...]=(high[-low])|...
#                             symbols after the name represent different modifiers:
#                                 ~ sign extension, can only appear once
#                                 < left shift by 'num' amount on extraction, can only appear once
#                                 ! mark 'num' as an invalid input for this variable
EOM

  # Sort alphabetically by instruction mnemonic so the output is
  # deterministic regardless of where the instruction files live (moving a
  # file between extension directories must not change this table). Each
  # line begins with the instruction name, so sorting the full lines orders
  # by mnemonic and keeps an instruction's multi-row entries (e.g.
  # "common,32"/"common,64") grouped and stably ordered.
  lines.sort!

  header + lines.join("\n") + "\n"
end

#get_encoding(inst, base) ⇒ Object 



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# File 'lib/udb-gen/generators/inst_table/table_builder.rb', line 23

def get_encoding(inst, base)
  return [] unless inst.defined_in_base?(base)

  fields = []

  enc_obj = inst.encoding(base)
  fixed = enc_obj.opcode_fields.map do |fo|
    "#{fo.name}<#{fo.range.first}"
  end

  fields.append(fixed.join("|"))

  dvs = inst.decode_variables(base)

  dvs.each do |d|
    field = "#{d.name}"

    if d.sext?
      field += "~"
    end

    unless d.excludes.empty?
      field += "!#{d.excludes.join('!')}"
    end

    if d.left_shift > 0
      field += "<#{d.left_shift}"
    end

    field += "=#{d.location}"

    fields.append(field)
  end

  return fields
end