;;;; x86 VM definitions of various system hacking operations

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB!VM")

;;;; type frobbing VOPs

(define-vop (widetag-of)
  (:translate widetag-of)
  (:policy :fast-safe)
  (:args (object :scs (descriptor-reg)))
  (:temporary (:sc unsigned-reg :offset rax-offset :target result
                   :to (:result 0)) rax)
  (:results (result :scs (unsigned-reg)))
  (:result-types positive-fixnum)
  (:generator 6
    (inst movzx rax (reg-in-size object :byte))
    (inst and al-tn lowtag-mask)
    (inst cmp al-tn other-pointer-lowtag)
    (inst jmp :e OTHER-PTR)
    (inst cmp al-tn fun-pointer-lowtag)
    (inst jmp :e FUNCTION-PTR)

    ;; Pick off fixnums.
    (inst test al-tn fixnum-tag-mask)
    (inst jmp :e DONE)

    ;; Pick off structures and list pointers.
    (inst test al-tn 2)
    (inst jmp :ne DONE)

    ;; must be an other immediate
    (inst movzx rax (reg-in-size object :byte))
    (inst jmp DONE)

    FUNCTION-PTR
    (load-type rax object (- fun-pointer-lowtag))
    (inst jmp DONE)

    OTHER-PTR
    (load-type rax object (- other-pointer-lowtag))

    DONE
    (move result rax)))

#!+compact-instance-header
;; ~20 instructions vs. 35
(define-vop (layout-of) ; no translation
    (:policy :fast-safe)
    (:args (object :scs (descriptor-reg))
           (layouts :scs (constant)))
    (:temporary (:sc unsigned-reg :offset rax-offset) rax)
    (:results (result :scs (descriptor-reg)))
    (:generator 6
      ;; Lowtag: #b0011 instance
      ;;         #b0111 list
      ;;         #b1011 fun
      ;;         #b1111 other
      (inst mov  rax object)
      (inst xor  (reg-in-size rax :byte) #b0011)
      (inst test (reg-in-size rax :byte) #b0111)
      (inst jmp  :ne try-other)
      ;; It's an instance or function. Both have the layout in the header.
      (inst and  (reg-in-size rax :byte) #b11110111)
      (inst mov  (reg-in-size result :dword) (make-ea :dword :base rax :disp 4))
      (inst jmp  done)
      TRY-OTHER
      (inst xor  (reg-in-size rax :byte) #b1100)
      (inst test (reg-in-size rax :byte) #b1111)
      (inst jmp  :ne imm-or-list)
      ;; It's an other-pointer. Read the widetag.
      (inst movzx (reg-in-size rax :dword) (make-ea :byte :base rax))
      (inst jmp  load-from-vector)
      IMM-OR-LIST
      (inst cmp  object nil-value)
      (inst jmp  :eq NULL)
      (inst movzx (reg-in-size rax :dword) (reg-in-size object :byte))
      LOAD-FROM-VECTOR
      (inst mov  result layouts)
      (inst mov  (reg-in-size result :dword)
            (make-ea :dword :base result
                            :index rax :scale 8
                            :disp (+ (ash vector-data-offset word-shift)
                                     (- other-pointer-lowtag))))
      (inst jmp  done)
      NULL
      (inst mov  result (make-fixup (find-layout 'null) :layout))
      DONE))

(define-vop (%other-pointer-widetag)
  (:translate %other-pointer-widetag)
  (:policy :fast-safe)
  (:args (object :scs (descriptor-reg)))
  (:results (result :scs (unsigned-reg)))
  (:result-types positive-fixnum)
  (:generator 6
    (load-type result object (- other-pointer-lowtag))))

(define-vop (fun-subtype)
  (:translate fun-subtype)
  (:policy :fast-safe)
  (:args (function :scs (descriptor-reg)))
  (:results (result :scs (unsigned-reg)))
  (:result-types positive-fixnum)
  (:generator 6
    (load-type result function (- fun-pointer-lowtag))))

(define-vop (get-header-data)
  (:translate get-header-data)
  (:policy :fast-safe)
  (:args (x :scs (descriptor-reg)))
  (:results (res :scs (unsigned-reg)))
  (:result-types positive-fixnum)
  (:generator 6
    (loadw res x 0 other-pointer-lowtag)
    (inst shr res n-widetag-bits)))

(define-vop (get-closure-length)
  (:translate get-closure-length)
  (:policy :fast-safe)
  (:args (x :scs (descriptor-reg)))
  (:results (res :scs (any-reg)))
  (:result-types positive-fixnum)
  (:generator 6
    (let ((res (reg-in-size res :dword)))
      (inst movzx res
            (make-ea :word :base x :disp (1+ (- fun-pointer-lowtag))))
      (inst btr res 15) ; Clear the NAMEDP header bit
      (inst shl res n-fixnum-tag-bits))))

(define-vop (set-header-data)
  (:translate set-header-data)
  (:policy :fast-safe)
  (:args (x :scs (descriptor-reg) :target res :to (:result 0))
         (data :scs (any-reg) :target eax))
  (:arg-types * positive-fixnum)
  (:results (res :scs (descriptor-reg)))
  (:temporary (:sc unsigned-reg :offset eax-offset
                   :from (:argument 1) :to (:result 0)) eax)
  (:generator 6
    (move eax data)
    (inst shl eax (- n-widetag-bits n-fixnum-tag-bits))
    (inst mov al-tn (make-ea :byte :base x :disp (- other-pointer-lowtag)))
    (storew eax x 0 other-pointer-lowtag)
    (move res x)))

(define-vop (get-header-data-high)
  (:translate get-header-data-high)
  (:policy :fast-safe)
  (:args (x :scs (descriptor-reg)))
  (:results (res :scs (any-reg)))
  (:result-types positive-fixnum)
  (:generator 6
    (inst mov (reg-in-size res :dword)
          (make-ea :dword :base x :disp (- 4 other-pointer-lowtag)))
    (inst shl res n-fixnum-tag-bits)))

;;; Swap the high half of the header word of an object
;;; that has OTHER-POINTER-LOWTAG
(define-vop (cas-header-data-high)
  (:args (object :scs (descriptor-reg) :to :eval)
         (old :scs (unsigned-reg) :target rax)
         (new :scs (unsigned-reg)))
  (:policy :fast-safe)
  (:translate cas-header-data-high)
  (:temporary (:sc descriptor-reg :offset rax-offset
               :from (:argument 1) :to :result :target result) rax)
  (:arg-types * unsigned-num unsigned-num)
  (:results (result :scs (any-reg)))
  (:result-types positive-fixnum)
  (:generator 5
     (move rax old)
     (inst cmpxchg (make-ea :dword :base object
                            :disp (- 4 other-pointer-lowtag))
           (reg-in-size new :dword) :lock)
     (inst lea result
           (make-ea :qword :index rax
                    :scale (ash 1 n-fixnum-tag-bits)))))

(define-vop (pointer-hash)
  (:translate pointer-hash)
  (:args (ptr :scs (any-reg descriptor-reg) :target res))
  (:results (res :scs (any-reg descriptor-reg)))
  (:policy :fast-safe)
  (:generator 1
    (move res ptr)
    ;; Mask the lowtag, and shift the whole address into a positive
    ;; fixnum.
    (inst and res (lognot lowtag-mask))
    (inst shr res 1)))

;;;; allocation

(define-vop (binding-stack-pointer-sap)
  (:results (int :scs (sap-reg)))
  (:result-types system-area-pointer)
  (:translate binding-stack-pointer-sap)
  (:policy :fast-safe)
  (:generator 1
    (load-binding-stack-pointer int)))

(define-vop (control-stack-pointer-sap)
  (:results (int :scs (sap-reg)))
  (:result-types system-area-pointer)
  (:translate control-stack-pointer-sap)
  (:policy :fast-safe)
  (:generator 1
    (move int rsp-tn)))

;;;; code object frobbing

(define-vop (code-instructions)
  (:translate code-instructions)
  (:policy :fast-safe)
  (:args (code :scs (descriptor-reg) :to (:result 0)))
  (:results (sap :scs (sap-reg) :from (:argument 0)))
  (:result-types system-area-pointer)
  (:generator 10
    ;; Perform an unaligned 16-bit read to extract the payload length.
    ;; There are only 15 bits of precision, but the high bit is always 0
    ;; so it doesn't need masking.
    (inst movzx (reg-in-size sap :dword)
              (make-ea :word :base code :disp (- 1 other-pointer-lowtag)))
    (inst lea sap (make-ea :byte :base code :index sap
                           :scale n-word-bytes
                           :disp (- other-pointer-lowtag)))))

(define-vop (compute-fun)
  (:args (code :scs (descriptor-reg) :to (:result 0))
         (offset :scs (signed-reg unsigned-reg) :to (:result 0)))
  (:arg-types * positive-fixnum)
  (:results (func :scs (descriptor-reg) :from (:argument 0)))
  (:generator 10
    (inst movzx (reg-in-size func :dword)
              (make-ea :word :base code :disp (- 1 other-pointer-lowtag)))
    (inst lea func
          (make-ea :byte :base offset :index func
                   :scale n-word-bytes
                   :disp (- fun-pointer-lowtag other-pointer-lowtag)))
    (inst add func code)))

;;; This vop is quite magical - because 'closure-fun' is a raw program counter,
;;; as soon as it's loaded into a register, it prevents the underlying fun from
;;; being transported by GC. It's even subtler in that sense than COMPUTE-FUN,
;;; which doesn't pin a *different* object produced from thin air.
;;; (It's output operand is embedded in the object pointed to by its input)
(define-vop (%closure-fun)
  (:policy :fast-safe)
  (:translate %closure-fun)
  (:args (function :scs (descriptor-reg)))
  (:results (result :scs (descriptor-reg)))
  (:generator 3
    (loadw result function closure-fun-slot fun-pointer-lowtag)
    (inst lea result
          (make-ea :byte :base result
                   :disp (- fun-pointer-lowtag
                            (* simple-fun-code-offset n-word-bytes))))))

;;;; symbol frobbing
(defun load-symbol-info-vector (result symbol temp)
  (loadw result symbol symbol-info-slot other-pointer-lowtag)
  ;; If RES has list-pointer-lowtag, take its CDR. If not, use it as-is.
  ;; This CMOV safely reads from memory when it does not move, because if
  ;; there is an info-vector in the slot, it has at least one element.
  ;; This would compile to almost the same code without a VOP,
  ;; but using a jmp around a mov instead.
  (inst lea temp (make-ea :dword :base result :disp (- list-pointer-lowtag)))
  (inst test (reg-in-size temp :byte) lowtag-mask)
  (inst cmov :e result
        (make-ea-for-object-slot result cons-cdr-slot list-pointer-lowtag)))

(define-vop (symbol-info-vector)
  (:policy :fast-safe)
  (:translate symbol-info-vector)
  (:args (x :scs (descriptor-reg)))
  (:results (res :scs (descriptor-reg)))
  (:temporary (:sc unsigned-reg :offset rax-offset) rax)
  (:generator 1
    (load-symbol-info-vector res x rax)))

(define-vop (symbol-plist)
  (:policy :fast-safe)
  (:translate symbol-plist)
  (:args (x :scs (descriptor-reg)))
  (:results (res :scs (descriptor-reg)))
  (:temporary (:sc unsigned-reg) temp)
  (:generator 1
    (loadw res x symbol-info-slot other-pointer-lowtag)
    ;; Instruction pun: (CAR x) is the same as (VECTOR-LENGTH x)
    ;; so if the info slot holds a vector, this gets a fixnum- it's not a plist.
    (loadw res res cons-car-slot list-pointer-lowtag)
    (inst mov temp nil-value)
    (inst test (reg-in-size res :byte) fixnum-tag-mask)
    (inst cmov :e res temp)))

;;;; other miscellaneous VOPs

(defknown sb!unix::receive-pending-interrupt () (values))
(define-vop (sb!unix::receive-pending-interrupt)
  (:policy :fast-safe)
  (:translate sb!unix::receive-pending-interrupt)
  (:generator 1
    (inst break pending-interrupt-trap)))

#!+sb-thread
;; 29 signed bits is the max before shifting left by 3 that fits in the
;; 'displacement' of an EA. This is hugely generous.
;; We need negative indices to reference the interrupt contexts
(defknown current-thread-offset-sap ((signed-byte 29))
  system-area-pointer (flushable))

#!+sb-thread
(progn
(define-vop (current-thread-offset-sap/c)
  (:results (sap :scs (sap-reg)))
  (:result-types system-area-pointer)
  (:translate current-thread-offset-sap)
  (:info n)
  (:arg-types (:constant signed-byte))
  (:policy :fast-safe)
  (:generator 1
    (inst mov sap (thread-tls-ea (ash n 3)))))
(define-vop (current-thread-offset-sap)
  (:results (sap :scs (sap-reg)))
  (:result-types system-area-pointer)
  (:translate current-thread-offset-sap)
  (:args (n :scs (any-reg) :target sap))
  (:arg-types tagged-num)
  (:policy :fast-safe)
  (:generator 2
    (inst mov sap
          (make-ea :qword :base thread-base-tn :index n
                          :scale (ash 1 (- word-shift n-fixnum-tag-bits)))))))

(define-vop (halt)
  (:generator 1
    (inst break halt-trap)))

;;;; Miscellany

;;; the RDTSC instruction (present on Pentium processors and
;;; successors) allows you to access the time-stamp counter, a 64-bit
;;; model-specific register that counts executed cycles. The
;;; instruction returns the low cycle count in EAX and high cycle
;;; count in EDX.
;;;
;;; In order to obtain more significant results on out-of-order
;;; processors (such as the Pentium II and later), we issue a
;;; serializing CPUID instruction before and after reading the cycle
;;; counter. This instruction is used for its side effect of emptying
;;; the processor pipeline, to ensure that the RDTSC instruction is
;;; executed once all pending instructions have been completed and
;;; before any others. CPUID writes to EBX and ECX in addition to EAX
;;; and EDX, so they need to be added as temporaries.
;;;
;;; Note that cache effects mean that the cycle count can vary for
;;; different executions of the same code (it counts cycles, not
;;; retired instructions). Furthermore, the results are per-processor
;;; and not per-process, so are unreliable on multiprocessor machines
;;; where processes can migrate between processors.
;;;
;;; This method of obtaining a cycle count has the advantage of being
;;; very fast (around 20 cycles), and of not requiring a system call.
;;; However, you need to know your processor's clock speed to translate
;;; this into real execution time.
;;;
;;; FIXME: This about the WITH-CYCLE-COUNTER interface a bit, and then
;;; perhaps export it from SB-SYS.

(defknown %read-cycle-counter () (values (unsigned-byte 32) (unsigned-byte 32)) ())

(define-vop (%read-cycle-counter)
  (:policy :fast-safe)
  (:translate %read-cycle-counter)
  (:temporary (:sc unsigned-reg :offset eax-offset :target lo) eax)
  (:temporary (:sc unsigned-reg :offset edx-offset :target hi) edx)
  (:temporary (:sc unsigned-reg :offset ebx-offset) ebx)
  (:temporary (:sc unsigned-reg :offset ecx-offset) ecx)
  (:ignore ebx ecx)
  (:results (hi :scs (unsigned-reg))
            (lo :scs (unsigned-reg)))
  (:result-types unsigned-num unsigned-num)
  (:generator 5
     (zeroize eax)
     ;; Intel docs seem quite consistent on only using CPUID before RDTSC,
     ;; not both before and after. Go figure.
     (inst cpuid)
     (inst rdtsc)
     (move lo eax)
     (move hi edx)))

(defmacro with-cycle-counter (&body body)
  "Returns the primary value of BODY as the primary value, and the
number of CPU cycles elapsed as secondary value. EXPERIMENTAL."
  (with-unique-names (hi0 hi1 lo0 lo1)
    `(multiple-value-bind (,hi0 ,lo0) (%read-cycle-counter)
       (values (locally ,@body)
               (multiple-value-bind (,hi1 ,lo1) (%read-cycle-counter)
                 (+ (ash (- ,hi1 ,hi0) 32)
                    (- ,lo1 ,lo0)))))))

#!+sb-dyncount
(define-vop (count-me)
  (:args (count-vector :scs (descriptor-reg)))
  (:info index)
  (:generator 0
    (inst inc (make-ea :qword :base count-vector
                       :disp (- (* (+ vector-data-offset index) n-word-bytes)
                                other-pointer-lowtag)))))

;;;; Memory barrier support

(define-vop (%compiler-barrier)
  (:policy :fast-safe)
  (:translate %compiler-barrier)
  (:generator 3))

(define-vop (%memory-barrier)
  (:policy :fast-safe)
  (:translate %memory-barrier)
  (:generator 3
    (inst mfence)))

(define-vop (%read-barrier)
  (:policy :fast-safe)
  (:translate %read-barrier)
  (:generator 3))

(define-vop (%write-barrier)
  (:policy :fast-safe)
  (:translate %write-barrier)
  (:generator 3))

(define-vop (%data-dependency-barrier)
  (:policy :fast-safe)
  (:translate %data-dependency-barrier)
  (:generator 3))

(define-vop (pause)
  (:translate spin-loop-hint)
  (:policy :fast-safe)
  (:generator 0
    (inst pause)))

(defknown %cpu-identification ((unsigned-byte 32) (unsigned-byte 32))
    (values (unsigned-byte 32) (unsigned-byte 32)
            (unsigned-byte 32) (unsigned-byte 32)))

;; This instruction does in fact not utilize all bits of the full width (Rxx)
;; regs so it would be wonderful to share this verbatim with x86 32-bit.
(define-vop (%cpu-identification)
  (:policy :fast-safe)
  (:translate %cpu-identification)
  (:args (function :scs (unsigned-reg) :target eax)
         (subfunction :scs (unsigned-reg) :target ecx))
  (:arg-types unsigned-num unsigned-num)
  (:results (a :scs (unsigned-reg))
            (b :scs (unsigned-reg))
            (c :scs (unsigned-reg))
            (d :scs (unsigned-reg)))
  (:result-types unsigned-num unsigned-num unsigned-num unsigned-num)
  (:temporary (:sc unsigned-reg :from (:argument 0) :to (:result 0)
               :offset eax-offset) eax)
  (:temporary (:sc unsigned-reg :from (:argument 1) :to (:result 2)
               :offset ecx-offset) ecx)
  (:temporary (:sc unsigned-reg :from :eval :to (:result 3)
               :offset edx-offset) edx)
  (:temporary (:sc unsigned-reg :from :eval :to (:result 1)
               :offset ebx-offset) ebx)
  (:generator 5
   (move eax function)
   (move ecx subfunction)
   (inst cpuid)
   (move a eax)
   (move b ebx)
   (move c ecx)
   (move d edx)))
