Specialize in Gem5

Problem to solve

decoder/one_byte_opcodes.isa => build/X86/arch/x86/generated/decode-method.cc.inc
MOV(Bv, Iv)                  => x86_macroop::MOV_R_I(...)

decoder/one_byte_opcodes.isa:

'X86ISA::OneByteOpcode': decode OPCODE_OP_TOP5 {
  format Inst {
    0x17: MOV(Bv,Iv);
}}

format Inst is defined in src/arch/x86/isa/formats/multi.isa:

def format Inst(*opTypeSet) {{
    blocks = specializeInst(Name, list(opTypeSet), EmulEnv())
    (header_output, decoder_output,
     decode_block, exec_output) = blocks.makeList()
}};

specializeInst is defined in src/arch/x86/isa/specialize.isa:

def specializeInst(Name, opTypes, env):
  ...

Here Name = "MOV", opTypes = ("Bv", "Iv").

r prefixed opType is reg, others are tag. Tag specialization are listed as below.

Note: '_P' means RIP relative addressing

Available data size is defined in src/arch/x86/isa/macroop.isa: getAllocator

string specialization

See gem5/src/arch/x86/isa/formats/string.isa

_E for repe, _N for repne, e.g. STOS_E_M