fpucosh.asm

来自「工欲善其事」· 汇编 代码 · 共 130 行

; #########################################################################
;
;                             FpuCosh
;
;##########################################################################

  ; -----------------------------------------------------------------------
  ; This procedure was written by Raymond Filiatreault, December 2002
  ;
  ;     cosh(Src) = [e^(Src) + e^(-Src)]/2 -> Dest    (see FpuEexpX for e^x)
  ;
  ; This FpuCosh function computes the hyperbolic cosine of a number (Src)
  ; with the FPU and returns the result as an 80-bit REAL number at the
  ; specified destination (the FPU itself or a memory location), unless
  ; an invalid operation is reported by the FPU or the definition of the
  ; parameters (with uID) is invalid.
  ;
  ; The source can be an 80-bit REAL number from the FPU itself or from
  ; memory, an immediate DWORD value or one in memory.
  ;
  ; The source is not checked for validity. This is the programmer's
  ; responsibility.
  ;
  ; Only EAX is used to return error or success. All other registers are
  ; preserved.
  ;
  ; -----------------------------------------------------------------------

    .486
    .model flat, stdcall  ; 32 bit memory model
    option casemap :none  ; case sensitive

    include Fpu.inc

    .data
    
    tempdw  dd    0
    stword  dw    0

    .code

; #########################################################################

FpuCosh proc public lpSrc:DWORD, lpDest:DWORD, uID:DWORD
        
;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
;
; Because a library is assembled before its functions are called, all
; references to external memory data must be qualified for the expected
; size of that data so that the proper code is generated.
;
;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

; the FPU will be initialized only if the source parameter is not taken
; from the FPU itself.

      fclex                   ;clear exception flags on FPU
      test  uID,SRC1_FPU      ;is Src taken from FPU?
      jnz   dest0             ;go complete process
      finit
      
;----------------------------------------
;check source for Src and load it to FPU
;----------------------------------------

      mov   eax,lpSrc
      test  uID,SRC1_REAL     ;is Src an 80-bit REAL in memory?
      jz    @F
      fld   tbyte ptr [eax]
      jmp   dest0             ;go complete process
@@:
      test  uID,SRC1_DMEM     ;is Src a 32-bit integer in memory?
      jz    @F
      fild  dword ptr [eax]
      jmp   dest0             ;go complete process
@@:
      test  uID,SRC1_DIMM     ;is Src an immediate 32-bit integer?
      jz    srcerr            ;no correct flag for Src
      mov   tempdw,eax
      fild  tempdw
      jmp   dest0             ;go complete process
      
srcerr:
      finit
      xor   eax,eax
      ret

dest0:
      fldl2e
      fmul                    ;log2(e)*Src
      fld   st(0)
      frndint
      fxch
      fsub  st,st(1)
      f2xm1
      fld1
      fadd
      fscale                  ;-> antilog[log2(e)*Src] = e^(Src)
      fxch
      fstp  st(0)             ;get rid of scaling factor

      fld   st(0)             ;copy it to get the reciprocal
      fld1
      fxch
      fdiv                    ;1/e^(Src) = e^(-Src)
      fadd                    ;e^(Src) + e^(-Src)
      fld1
      fadd  st,st(0)          ;1+1=2
      fdiv                    ;-> [e^(Src) + e^(-Src)]/2 = cosh(Src)

      fstsw stword            ;retrieve exception flags from FPU
      fwait
      test  stword,1          ;test for invalid operation
      jnz   srcerr            ;clean-up and return error

      mov   eax,lpDest
      test  uID,DEST_FPU      ;check where result should be stored
      jnz   @F                ;leave result on FPU if so indicated
      fstp  tbyte ptr [eax]   ;store result at specified address

@@:
      or    al,1              ;to insure EAX!=0
      ret
    
FpuCosh endp

; #########################################################################

end