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page ,132
subttl emfmisc.asm - Miscellaneous Operations
;***
;emfmisc.asm - Miscellaneous Operations
;
; Copyright (c) 1987-89, Microsoft Corporation
;
;Purpose:
; Miscellaneous Operations: FABS, FCHS, DupTOS, FSCALE, FXCHG
;
;
; This Module contains Proprietary Information of Microsoft
; Corporation and should be treated as Confidential.
;
;Revision History:
; See emulator.hst
;
;*******************************************************************************
ProfBegin FMISC
pub eFABS
MOV esi,[CURstk] ; point to TOS
AND byte ptr Flag[esi],0FFH - Sign ; mask off sign
RET
pub eFCHS
MOV esi,[CURstk] ; point to TOS
XOR byte ptr Flag[esi],Sign ; toggle the sign
RET
; FLDCW and FSTCW should only be used in a nested fashion
; and should never change the denormal and invalid masks (in real 8087)
;
; FSTCW old
; FLDCW new ; new and old have same denormal/invalid masks
; ...
; FLDCW old
pub eFLDCW
LDUS2AX ; Fetch control word from user memory
MOV [ControlWord],AX ; Store in the emulated control word
MOV [UserControlWord],AX ; Store in the user control word
RET
pub eFSTCW
MOV AX,[UserControlWord] ; Fetch user control word
MOV edi,esi
STAX2US ; Store into user memory
RET
pub eFSTSW
MOV AX,[StatusWord] ; Fetch emulated Status word
MOV edi,esi
STAX2US ; Store into user memory
RET
pub eFSCALE ; NOS is treated as short integer and TOS gets
MOV esi,[CURstk] ; its exponent bumped by that amount
MOV edi,esi
ChangeDIfromTOStoNOS
MOV CL,15
MOV AL,Expon[edi] ; Assume word integer
AND AL,0FH ; Assume exp is positive and in range
SUB CL,AL ; Generate shift count for mantissa
MOV AX,MB6[edi] ; MSW will contain the whole integer
SHR AX,CL ; AX is now the integer
MOV CL,Flag[edi] ; Get the sign for the integer
OR CL,CL
JNS short GotExponInc
NEG AX
pub GotExponInc
ADD AX,Expon[esi]
JO short ExpOverflowed
CMP AX,IexpMax - IexpBias
JGE short ScaledToInfinity
CMP AX,IexpMin - IexpBias
JLE short ScaledToZero
pub ScaleReturn
MOV Expon[esi],AX
RET
pub ExpOverflowed
JNS short ScaledToZero
pub ScaledToInfinity
MOV AX,IexpMax - IexpBias
MOV byte ptr Tag[esi],Special + ZROorINF
JMP short ScaleReturn
pub ScaledToZero
MOV AX,IexpMin - IexpBias
MOV byte ptr Tag[esi],ZROorINF
JMP short ScaleReturn
ProfEnd FMISC
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