Require Import Coqlib Maps.
Require Import AST Integers Values Events Memory Globalenvs Smallstep.
Require Import Op Locations Conventions.

Abstract syntax

Definition node := positive.

Inductive instruction: Type :=
  | Lop (op: operation) (args: list mreg) (res: mreg)
  | Lload (chunk: memory_chunk) (addr: addressing) (args: list mreg) (dst: mreg)
  | Lgetstack (sl: slot) (ofs: Z) (ty: typ) (dst: mreg)
  | Lsetstack (src: mreg) (sl: slot) (ofs: Z) (ty: typ)
  | Lstore (chunk: memory_chunk) (addr: addressing) (args: list mreg) (src: mreg)
  | Lcall (sg: signature) (ros: mreg + ident)
  | Ltailcall (sg: signature) (ros: mreg + ident)
  | Lbuiltin (ef: external_function) (args: list (builtin_arg loc)) (res: builtin_res mreg)
  | Lbranch (s: node)
  | Lcond (cond: condition) (args: list mreg) (s1 s2: node)
  | Ljumptable (arg: mreg) (tbl: list node)
  | Lreturn.

Definition bblock := list instruction.

Definition code: Type := PTree.t bblock.

Record function: Type := mkfunction {
  fn_sig: signature;
  fn_stacksize: Z;
  fn_code: code;
  fn_entrypoint: node
}.

Definition fundef := AST.fundef function.

Definition program := AST.program fundef unit.

Definition funsig (fd: fundef) :=
  match fd with
  | Internal f => fn_sig f
  | External ef => ef_sig ef
  end.

Operational semantics

Definition genv := Genv.t fundef unit.
Definition locset := Locmap.t.


Definition call_regs (caller: locset) : locset :=
  fun (l: loc) =>
    match l with
    | R r => caller (R r)
    | S Local ofs ty => Vundef
    | S Incoming ofs ty => caller (S Outgoing ofs ty)
    | S Outgoing ofs ty => Vundef
    end.


Definition return_regs (caller callee: locset) : locset :=
  fun (l: loc) =>
    match l with
    | R r => if is_callee_save r then caller (R r) else callee (R r)
    | S sl ofs ty => caller (S sl ofs ty)
    end.


Inductive stackframe : Type :=
  | Stackframe:
      forall (f: function) (* calling function *)
             (sp: val) (* stack pointer in calling function *)
             (ls: locset) (* location state in calling function *)
             (bb: bblock), (* continuation in calling function *)
      stackframe.

Inductive state : Type :=
  | State:
      forall (stack: list stackframe) (* call stack *)
             (f: function) (* function currently executing *)
             (sp: val) (* stack pointer *)
             (pc: node) (* current program point *)
             (ls: locset) (* location state *)
             (m: mem), (* memory state *)
      state
  | Block:
      forall (stack: list stackframe) (* call stack *)
             (f: function) (* function currently executing *)
             (sp: val) (* stack pointer *)
             (bb: bblock) (* current basic block *)
             (ls: locset) (* location state *)
             (m: mem), (* memory state *)
      state
  | Callstate:
      forall (stack: list stackframe) (* call stack *)
             (f: fundef) (* function to call *)
             (ls: locset) (* location state of caller *)
             (m: mem), (* memory state *)
      state
  | Returnstate:
      forall (stack: list stackframe) (* call stack *)
             (ls: locset) (* location state of callee *)
             (m: mem), (* memory state *)
      state.


Section RELSEM.

Variable ge: genv.

Definition reglist (rs: locset) (rl: list mreg) : list val :=
  List.map (fun r => rs (R r)) rl.

Fixpoint undef_regs (rl: list mreg) (rs: locset) : locset :=
  match rl with
  | nil => rs
  | r1 :: rl => Locmap.set (R r1) Vundef (undef_regs rl rs)
  end.

Definition destroyed_by_getstack (s: slot): list mreg :=
  match s with
  | Incoming => temp_for_parent_frame :: nil
  | _ => nil
  end.

Definition find_function (ros: mreg + ident) (rs: locset) : option fundef :=
  match ros with
  | inl r => Genv.find_funct ge (rs (R r))
  | inr symb =>
      match Genv.find_symbol ge symb with
      | None => None
      | Some b => Genv.find_funct_ptr ge b
      end
  end.


Definition parent_locset (stack: list stackframe) : locset :=
  match stack with
  | nil => Locmap.init Vundef
  | Stackframe f sp ls bb :: stack' => ls
  end.

Inductive step: state -> trace -> state -> Prop :=
  | exec_start_block: forall s f sp pc rs m bb,
      (fn_code f)!pc = Some bb ->
      step (State s f sp pc rs m)
        E0 (Block s f sp bb rs m)
  | exec_Lop: forall s f sp op args res bb rs m v rs',
      eval_operation ge sp op (reglist rs args) m = Some v ->
      rs' = Locmap.set (R res) v (undef_regs (destroyed_by_op op) rs) ->
      step (Block s f sp (Lop op args res :: bb) rs m)
        E0 (Block s f sp bb rs' m)
  | exec_Lload: forall s f sp chunk addr args dst bb rs m a v rs',
      eval_addressing ge sp addr (reglist rs args) = Some a ->
      Mem.loadv chunk m a = Some v ->
      rs' = Locmap.set (R dst) v (undef_regs (destroyed_by_load chunk addr) rs) ->
      step (Block s f sp (Lload chunk addr args dst :: bb) rs m)
        E0 (Block s f sp bb rs' m)
  | exec_Lgetstack: forall s f sp sl ofs ty dst bb rs m rs',
      rs' = Locmap.set (R dst) (rs (S sl ofs ty)) (undef_regs (destroyed_by_getstack sl) rs) ->
      step (Block s f sp (Lgetstack sl ofs ty dst :: bb) rs m)
        E0 (Block s f sp bb rs' m)
  | exec_Lsetstack: forall s f sp src sl ofs ty bb rs m rs',
      rs' = Locmap.set (S sl ofs ty) (rs (R src)) (undef_regs (destroyed_by_setstack ty) rs) ->
      step (Block s f sp (Lsetstack src sl ofs ty :: bb) rs m)
        E0 (Block s f sp bb rs' m)
  | exec_Lstore: forall s f sp chunk addr args src bb rs m a rs' m',
      eval_addressing ge sp addr (reglist rs args) = Some a ->
      Mem.storev chunk m a (rs (R src)) = Some m' ->
      rs' = undef_regs (destroyed_by_store chunk addr) rs ->
      step (Block s f sp (Lstore chunk addr args src :: bb) rs m)
        E0 (Block s f sp bb rs' m')
  | exec_Lcall: forall s f sp sig ros bb rs m fd,
      find_function ros rs = Some fd ->
      funsig fd = sig ->
      step (Block s f sp (Lcall sig ros :: bb) rs m)
        E0 (Callstate (Stackframe f sp rs bb :: s) fd rs m)
  | exec_Ltailcall: forall s f sp sig ros bb rs m fd rs' m',
      rs' = return_regs (parent_locset s) rs ->
      find_function ros rs' = Some fd ->
      funsig fd = sig ->
      Mem.free m sp 0 f.(fn_stacksize) = Some m' ->
      step (Block s f (Vptr sp Ptrofs.zero) (Ltailcall sig ros :: bb) rs m)
        E0 (Callstate s fd rs' m')
  | exec_Lbuiltin: forall s f sp ef args res bb rs m vargs t vres rs' m',
      eval_builtin_args ge rs sp m args vargs ->
      external_call ef ge vargs m t vres m' ->
      rs' = Locmap.setres res vres (undef_regs (destroyed_by_builtin ef) rs) ->
      step (Block s f sp (Lbuiltin ef args res :: bb) rs m)
         t (Block s f sp bb rs' m')
  | exec_Lbranch: forall s f sp pc bb rs m,
      step (Block s f sp (Lbranch pc :: bb) rs m)
        E0 (State s f sp pc rs m)
  | exec_Lcond: forall s f sp cond args pc1 pc2 bb rs b pc rs' m,
      eval_condition cond (reglist rs args) m = Some b ->
      pc = (if b then pc1 else pc2) ->
      rs' = undef_regs (destroyed_by_cond cond) rs ->
      step (Block s f sp (Lcond cond args pc1 pc2 :: bb) rs m)
        E0 (State s f sp pc rs' m)
  | exec_Ljumptable: forall s f sp arg tbl bb rs m n pc rs',
      rs (R arg) = Vint n ->
      list_nth_z tbl (Int.unsigned n) = Some pc ->
      rs' = undef_regs (destroyed_by_jumptable) rs ->
      step (Block s f sp (Ljumptable arg tbl :: bb) rs m)
        E0 (State s f sp pc rs' m)
  | exec_Lreturn: forall s f sp bb rs m m',
      Mem.free m sp 0 f.(fn_stacksize) = Some m' ->
      step (Block s f (Vptr sp Ptrofs.zero) (Lreturn :: bb) rs m)
        E0 (Returnstate s (return_regs (parent_locset s) rs) m')
  | exec_function_internal: forall s f rs m m' sp rs',
      Mem.alloc m 0 f.(fn_stacksize) = (m', sp) ->
      rs' = undef_regs destroyed_at_function_entry (call_regs rs) ->
      step (Callstate s (Internal f) rs m)
        E0 (State s f (Vptr sp Ptrofs.zero) f.(fn_entrypoint) rs' m')
  | exec_function_external: forall s ef t args res rs m rs' m',
      args = map (fun p => Locmap.getpair p rs) (loc_arguments (ef_sig ef)) ->
      external_call ef ge args m t res m' ->
      rs' = Locmap.setpair (loc_result (ef_sig ef)) res rs ->
      step (Callstate s (External ef) rs m)
         t (Returnstate s rs' m')
  | exec_return: forall f sp rs1 bb s rs m,
      step (Returnstate (Stackframe f sp rs1 bb :: s) rs m)
        E0 (Block s f sp bb rs m).

End RELSEM.


Inductive initial_state (p: program): state -> Prop :=
  | initial_state_intro: forall b f m0,
      let ge := Genv.globalenv p in
      Genv.init_mem p = Some m0 ->
      Genv.find_symbol ge p.(prog_main) = Some b ->
      Genv.find_funct_ptr ge b = Some f ->
      funsig f = signature_main ->
      initial_state p (Callstate nil f (Locmap.init Vundef) m0).

Inductive final_state: state -> int -> Prop :=
  | final_state_intro: forall rs m retcode,
      Locmap.getpair (map_rpair R (loc_result signature_main)) rs = Vint retcode ->
      final_state (Returnstate nil rs m) retcode.

Definition semantics (p: program) :=
  Semantics step (initial_state p) final_state (Genv.globalenv p).

Operations over LTL

Fixpoint successors_block (b: bblock) : list node :=
  match b with
  | nil => nil (* should never happen *)
  | Ltailcall _ _ :: _ => nil
  | Lbranch s :: _ => s :: nil
  | Lcond _ _ s1 s2 :: _ => s1 :: s2 :: nil
  | Ljumptable _ tbl :: _ => tbl
  | Lreturn :: _ => nil
  | instr :: b' => successors_block b'
  end.