help.toml

[meta]
# Name of the ISA/extension
name = "My sample RISC-V extension"
# ISA letter code, use Z for non one-letter names
code = "Zhelp"
# Version on the specification document this is based on
spec = "Help spec 1.0"
# Required base ISAs
#requires = ["RV32I"]

[consts]
# these will be substituted in where numbers are expected and strings are provided
EVERYTHING = 42 

[registers]
[registers.names]
# Reg# = Array(Name, [Optional ABI Name], [Optional extra parsed names])
45 = ["x45" , "ufhr", "ufhd"]
46 = ["x46" , "ufr", "ufd"]

[registers.lengths]
# Reg# = Reg size in bits
45 = "XLEN"
46 = 128

[instruction_formats]
# [instruction_formats.Format_Name]
[instruction_formats.R]
# Field name = { type = "value/register", length = <total field size in bits>, encoding = [[vlast,vfirst,ifirst],... }
# Encoding: copies [vlast:vfirst] (inclusive ranges) bits from value
# as [ifirst+vlast-vfirst:ifirst] bits of the encoded instruction
# Can specify multiple copies for multiple sub-fields encoding the same value
opcode = { type = "value", length = 7, encoding = [[6,0,0]] }

[instruction_formats.U]
opcode = { type = "value", length = 7, encoding = [[6,0,0]] }
rd = { type = "register", length = 5, encoding = [[4,0,7]] }
imm = { type = "value", length = 32, encoding = [[31,12,12]] }

[instructions]
# [instructions.<name>]
[instructions.lui]
# One of the instruction formats defined above
format = "U"
# Fields of the format in order as they appear as arguments
args = ["rd", "imm"]
# Fields that are set to a constant value
fields = { opcode = 0b0110111 }
# All bits of the instruction should be covered by args and fields keys above combined