Module Machregs

Require Import String.
Require Import Coqlib.
Require Import Maps.
Require Import AST.
Require Import Integers.
Require Import Op.

Machine registers

The following type defines the machine registers that can be referenced as locations. These include:

Integer registers that can be allocated to RTL pseudo-registers.
Floating-point registers that can be allocated to RTL pseudo-registers.
The special FP0 register denoting the top of the X87 float stack.

The type mreg does not include special-purpose or reserved machine registers such as the stack pointer and the condition codes.

Inductive mreg: Type :=

Allocatable integer regs

Allocatable float regs

Special float reg

| FP0: mreg (* top of x87 FP stack *).

Lemma mreg_eq: forall (r1 r2: mreg), {r1 = r2} + {r1 <> r2}.

Proof.

decide equality. Defined.

Global Opaque mreg_eq.

Definition mreg_type (r: mreg): typ :=
  match r with
  | AX | BX | CX | DX | SI | DI | BP => Tany32
  | X0 | X1 | X2 | X3 | X4 | X5 | X6 | X7 | FP0 => Tany64
  end.

Local Open Scope positive_scope.

Module IndexedMreg <: INDEXED_TYPE.
  Definition t := mreg.
  Definition eq := mreg_eq.
  Definition index (r: mreg): positive :=
    match r with
    | AX => 1 | BX => 2 | CX => 3 | DX => 4 | SI => 5 | DI => 6 | BP => 7
    | X0 => 8 | X1 => 9 | X2 => 10 | X3 => 11
    | X4 => 12 | X5 => 13 | X6 => 14 | X7 => 15
    | FP0 => 16
    end.
  Lemma index_inj:
    forall r1 r2, index r1 = index r2 -> r1 = r2.

Proof.

destruct r1; destruct r2; simpl; intro; discriminate || reflexivity.
Qed.

End IndexedMreg.

Definition is_stack_reg (r: mreg) : bool :=
match r with FP0 => true | _ => false end.

Names of registers

Local Open Scope string_scope.

Definition register_names :=
  ("EAX", AX) :: ("EBX", BX) :: ("ECX", CX) :: ("EDX", DX) ::
  ("ESI", SI) :: ("EDI", DI) :: ("EBP", BP) ::
  ("XMM0", X0) :: ("XMM1", X1) :: ("XMM2", X2) :: ("XMM3", X3) ::
  ("XMM4", X4) :: ("XMM5", X5) :: ("XMM6", X6) :: ("XMM7", X7) ::
  ("ST0", FP0) :: nil.

Definition register_by_name (s: string) : option mreg :=
  let fix assoc (l: list (string * mreg)) : option mreg :=
    match l with
    | nil => None
    | (s1, r1) :: l' => if string_dec s s1 then Some r1 else assoc l'
    end
  in assoc register_names.

Destroyed registers, preferred registers

Definition destroyed_by_op (op: operation): list mreg :=
  match op with
  | Ocast8signed | Ocast8unsigned | Ocast16signed | Ocast16unsigned => AX :: nil
  | Omulhs => AX :: DX :: nil
  | Omulhu => AX :: DX :: nil
  | Odiv => AX :: DX :: nil
  | Odivu => AX :: DX :: nil
  | Omod => AX :: DX :: nil
  | Omodu => AX :: DX :: nil
  | Oshrximm _ => CX :: nil
  | Ocmp _ => AX :: CX :: nil
  | _ => nil
  end.

Definition destroyed_by_load (chunk: memory_chunk) (addr: addressing): list mreg :=
  nil.

Definition destroyed_by_store (chunk: memory_chunk) (addr: addressing): list mreg :=
  match chunk with
  | Mint8signed | Mint8unsigned => AX :: CX :: nil
  | _ => nil
  end.

Definition destroyed_by_cond (cond: condition): list mreg :=
  nil.

Definition destroyed_by_jumptable: list mreg :=
  nil.

Fixpoint destroyed_by_clobber (cl: list string): list mreg :=
  match cl with
  | nil => nil
  | c1 :: cl =>
      match register_by_name c1 with
      | Some r => r :: destroyed_by_clobber cl
      | None => destroyed_by_clobber cl
      end
  end.

Definition destroyed_by_builtin (ef: external_function): list mreg :=
  match ef with
  | EF_memcpy sz al =>
      if zle sz 32 then CX :: X7 :: nil else CX :: SI :: DI :: nil
  | EF_vstore (Mint8unsigned|Mint8signed) => AX :: CX :: nil
  | EF_builtin name sg =>
      if string_dec name "__builtin_write16_reversed"
      || string_dec name "__builtin_write32_reversed"
      then CX :: DX :: nil else nil
  | EF_inline_asm txt sg clob => destroyed_by_clobber clob
  | _ => nil
  end.

Definition destroyed_at_function_entry: list mreg :=
  DX :: FP0 :: nil.

Definition destroyed_by_setstack (ty: typ): list mreg :=
  match ty with
  | Tfloat | Tsingle => FP0 :: nil
  | _ => nil
  end.

Definition temp_for_parent_frame: mreg :=
  DX.

Definition mregs_for_operation (op: operation): list (option mreg) * option mreg :=
  match op with
  | Omulhs => (Some AX :: None :: nil, Some DX)
  | Omulhu => (Some AX :: None :: nil, Some DX)
  | Odiv => (Some AX :: Some CX :: nil, Some AX)
  | Odivu => (Some AX :: Some CX :: nil, Some AX)
  | Omod => (Some AX :: Some CX :: nil, Some DX)
  | Omodu => (Some AX :: Some CX :: nil, Some DX)
  | Oshl => (None :: Some CX :: nil, None)
  | Oshr => (None :: Some CX :: nil, None)
  | Oshru => (None :: Some CX :: nil, None)
  | Oshrximm _ => (Some AX :: nil, Some AX)
  | _ => (nil, None)
  end.

Definition mregs_for_builtin (ef: external_function): list (option mreg) * list (option mreg) :=
  match ef with
  | EF_memcpy sz al =>
     if zle sz 32 then (Some AX :: Some DX :: nil, nil) else (Some DI :: Some SI :: nil, nil)
  | EF_builtin name sg =>
     if string_dec name "__builtin_negl" then
       (Some DX :: Some AX :: nil, Some DX :: Some AX :: nil)
     else if string_dec name "__builtin_addl"
          || string_dec name "__builtin_subl" then
       (Some DX :: Some AX :: Some CX :: Some BX :: nil, Some DX :: Some AX :: nil)
     else if string_dec name "__builtin_mull" then
       (Some AX :: Some DX :: nil, Some DX :: Some AX :: nil)
     else
       (nil, nil)
  | _ => (nil, nil)
  end.

Global Opaque
    destroyed_by_op destroyed_by_load destroyed_by_store
    destroyed_by_cond destroyed_by_jumptable destroyed_by_builtin
    destroyed_by_setstack destroyed_at_function_entry temp_for_parent_frame
    mregs_for_operation mregs_for_builtin.

Two-address operations. Return true if the first argument and the result must be in the same location *and* are unconstrained by mregs_for_operation.