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