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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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