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Machine.fs
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(* File MicroC/Machine.fs
Instructions and code emission for a stack-based
abstract machine * sestoft@itu.dk 2009-09-23
Implementations of the machine are found in file MicroC/Machine.java
and MicroC/machine.c.
Must precede Comp.fs and Contcomp.fs in the VS Solution Explorer.
*)
module Machine
type label = string
// 汇编指令
type instr =
| Label of label (* symbolic label; pseudo-instruc. *)
| FLabel of int * label (* symbolic label; pseudo-instruc. *)
| CSTI of int (* constant *)
| CSTF of int
| CSTC of int
| OFFSET of int (* constant 偏移地址 x86 *)
| GVAR of int (* global var 全局变量 x86 *)
| ADD (* addition *)
| SUB (* subtraction *)
| MUL (* multiplication *)
| DIV (* division *)
| MOD (* modulus *)
| EQ (* equality: s[sp-1] == s[sp] *)
| LT (* less than: s[sp-1] < s[sp] *)
| NOT (* logical negation: s[sp] != 0 *)
| DUP (* duplicate stack top *)
| SWAP (* swap s[sp-1] and s[sp] *)
| LDI (* get s[s[sp]] *)
| STI (* set s[s[sp-1]] *)
| GETBP (* get bp *)
| GETSP (* get sp *)
| INCSP of int (* increase stack top by m *)
| GOTO of label (* go to label *)
| IFZERO of label (* go to label if s[sp] == 0 *)
| IFNZRO of label (* go to label if s[sp] != 0 *)
| CALL of int * label (* move m args up 1, push pc, jump *)
| TCALL of int * int * label (* move m args down n, jump *)
| RET of int (* pop m and return to s[sp] *)
| PRINTI (* print s[sp] as integer *)
| PRINTC (* print s[sp] as character *)
| LDARGS of int (* load command line args on stack *)
| STOP (* halt the abstract machine *)
(* Generate new distinct labels *)
// 返回两个函数 resetLabels , newLabel
let (resetLabels, newLabel) =
let lastlab = ref -1
((fun () -> lastlab := 0), (fun () -> (lastlab := 1 + !lastlab; "L" + (!lastlab).ToString())))
(* Simple environment operations *)
type 'data env = (string * 'data) list
let rec lookup env x =
match env with
| [] -> failwith (x + " not found")
| (y, v)::yr -> if x=y then v else lookup yr x
(* An instruction list is emitted in two phases:
* pass 1 builds an environment labenv mapping labels to addresses
* pass 2 emits the code to file, using the environment labenv to
resolve labels
*)
(* These numeric instruction codes must agree with Machine.java: *)
//机器码
//[<Literal>] 属性可以让
//该变量在模式匹配时候被匹配,否则匹配时只能用数值.不能用变量名
[<Literal>]
let CODECSTI = 0
[<Literal>]
let CODECSTF = 26
[<Literal>]
let CODECSTC = 27;
[<Literal>]
let CODEADD = 1
[<Literal>]
let CODESUB = 2
[<Literal>]
let CODEMUL = 3
[<Literal>]
let CODEDIV = 4
[<Literal>]
let CODEMOD = 5
[<Literal>]
let CODEEQ = 6
[<Literal>]
let CODELT = 7
[<Literal>]
let CODENOT = 8
[<Literal>]
let CODEDUP = 9
[<Literal>]
let CODESWAP = 10
[<Literal>]
let CODELDI = 11
[<Literal>]
let CODESTI = 12
[<Literal>]
let CODEGETBP = 13
[<Literal>]
let CODEGETSP = 14
[<Literal>]
let CODEINCSP = 15
[<Literal>]
let CODEGOTO = 16
[<Literal>]
let CODEIFZERO = 17
[<Literal>]
let CODEIFNZRO = 18
[<Literal>]
let CODECALL = 19
[<Literal>]
let CODETCALL = 20
[<Literal>]
let CODERET = 21
[<Literal>]
let CODEPRINTI = 22
[<Literal>]
let CODEPRINTC = 23
[<Literal>]
let CODELDARGS = 24
[<Literal>]
let CODESTOP = 25;
(* Bytecode emission, first pass: build environment that maps
each label to an integer address in the bytecode.
*)
//获得标签在机器码中的地址
let makelabenv (addr, labenv) instr =
match instr with
// 记录当前 (标签, 地址) ==> 到 labenv中
| Label lab -> (addr, (lab, addr) :: labenv)
| FLabel (m,lab) -> (addr, (lab, addr) :: labenv)
| CSTI i -> (addr+2, labenv)
| CSTF i -> (addr+2, labenv)
| CSTC i -> (addr+2, labenv)
| GVAR i -> (addr+2, labenv)
| OFFSET i -> (addr+2, labenv)
| ADD -> (addr+1, labenv)
| SUB -> (addr+1, labenv)
| MUL -> (addr+1, labenv)
| DIV -> (addr+1, labenv)
| MOD -> (addr+1, labenv)
| EQ -> (addr+1, labenv)
| LT -> (addr+1, labenv)
| NOT -> (addr+1, labenv)
| DUP -> (addr+1, labenv)
| SWAP -> (addr+1, labenv)
| LDI -> (addr+1, labenv)
| STI -> (addr+1, labenv)
| GETBP -> (addr+1, labenv)
| GETSP -> (addr+1, labenv)
| INCSP m -> (addr+2, labenv)
| GOTO lab -> (addr+2, labenv)
| IFZERO lab -> (addr+2, labenv)
| IFNZRO lab -> (addr+2, labenv)
| CALL(m,lab) -> (addr+3, labenv)
| TCALL(m,n,lab) -> (addr+4, labenv)
| RET m -> (addr+2, labenv)
| PRINTI -> (addr+1, labenv)
| PRINTC -> (addr+1, labenv)
| LDARGS m -> (addr+1, labenv)
| STOP -> (addr+1, labenv)
(* Bytecode emission, second pass: output bytecode as integers *)
//getlab 是得到标签所在地址的函数
//let getlab lab = lookup labenv lab
let rec emitints getlab instr ints =
match instr with
| Label lab -> ints
| FLabel (m,lab) -> ints
| CSTI i -> CODECSTI :: i :: ints
| CSTF i -> CODECSTF :: i :: ints
| CSTC i -> CODECSTC :: i :: ints
| GVAR i -> CODECSTI :: i :: ints
| OFFSET i -> CODECSTI :: i :: ints
| ADD -> CODEADD :: ints
| SUB -> CODESUB :: ints
| MUL -> CODEMUL :: ints
| DIV -> CODEDIV :: ints
| MOD -> CODEMOD :: ints
| EQ -> CODEEQ :: ints
| LT -> CODELT :: ints
| NOT -> CODENOT :: ints
| DUP -> CODEDUP :: ints
| SWAP -> CODESWAP :: ints
| LDI -> CODELDI :: ints
| STI -> CODESTI :: ints
| GETBP -> CODEGETBP :: ints
| GETSP -> CODEGETSP :: ints
| INCSP m -> CODEINCSP :: m :: ints
| GOTO lab -> CODEGOTO :: getlab lab :: ints
| IFZERO lab -> CODEIFZERO :: getlab lab :: ints
| IFNZRO lab -> CODEIFNZRO :: getlab lab :: ints
| CALL(m,lab) -> CODECALL :: m :: getlab lab :: ints
| TCALL(m,n,lab) -> CODETCALL :: m :: n :: getlab lab :: ints
| RET m -> CODERET :: m :: ints
| PRINTI -> CODEPRINTI :: ints
| PRINTC -> CODEPRINTC :: ints
| LDARGS m -> CODELDARGS :: ints
| STOP -> CODESTOP :: ints
(* Convert instruction list to int list in two passes:
Pass 1: build label environment
Pass 2: output instructions using label environment
*)
//通过对 code 的两次遍历,完成汇编指令到机器指令的转换
let code2ints (code : instr list) : int list =
//从前往后遍历 `汇编指令序列 code: instr list`
//得到 标签对应的地址,记录到 labenv中
let (_, labenv) = List.fold makelabenv (0, []) code
//getlab 是得到标签所在地址的函数
let getlab lab = lookup labenv lab
//从后往前 遍历 `汇编指令序列 code: instr list`
List.foldBack (emitints getlab) code []
let ntolabel (n:int) :label =
string(n)
//反编译
let rec decomp ints : instr list =
// printf "%A" ints
match ints with
| [] -> []
| CODEADD :: ints_rest -> ADD :: decomp ints_rest
| CODESUB :: ints_rest -> SUB :: decomp ints_rest
| CODEMUL :: ints_rest -> MUL :: decomp ints_rest
| CODEDIV :: ints_rest -> DIV :: decomp ints_rest
| CODEMOD :: ints_rest -> MOD :: decomp ints_rest
| CODEEQ :: ints_rest -> EQ :: decomp ints_rest
| CODELT :: ints_rest -> LT :: decomp ints_rest
| CODENOT :: ints_rest -> NOT :: decomp ints_rest
| CODEDUP :: ints_rest -> DUP :: decomp ints_rest
| CODESWAP :: ints_rest -> SWAP :: decomp ints_rest
| CODELDI :: ints_rest -> LDI :: decomp ints_rest
| CODESTI :: ints_rest -> STI :: decomp ints_rest
| CODEGETBP :: ints_rest -> GETBP :: decomp ints_rest
| CODEGETSP :: ints_rest -> GETSP :: decomp ints_rest
| CODEINCSP :: m :: ints_rest -> INCSP m :: decomp ints_rest
| CODEGOTO :: lab :: ints_rest -> GOTO (ntolabel lab) :: decomp ints_rest
| CODEIFZERO :: lab :: ints_rest -> IFZERO (ntolabel lab) :: decomp ints_rest
| CODEIFNZRO :: lab :: ints_rest -> IFNZRO (ntolabel lab) :: decomp ints_rest
| CODECALL :: m :: lab :: ints_rest -> CALL(m, ntolabel lab) :: decomp ints_rest
| CODETCALL :: m :: n :: lab :: ints_rest -> TCALL(m,n,ntolabel lab):: decomp ints_rest
| CODERET :: m :: ints_rest -> RET m :: decomp ints_rest
| CODEPRINTI :: ints_rest -> PRINTI :: decomp ints_rest
| CODEPRINTC :: ints_rest -> PRINTC :: decomp ints_rest
| CODELDARGS :: ints_rest -> LDARGS 0 :: decomp ints_rest
| CODESTOP :: ints_rest -> STOP :: decomp ints_rest
| CODECSTI :: i :: ints_rest -> CSTI i :: decomp ints_rest
| CODECSTF :: i :: ints_rest -> CSTF i :: decomp ints_rest
| _ -> printf "%A" ints; failwith "unknow code"