257 lines
4.7 KiB
NASM
257 lines
4.7 KiB
NASM
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page ,132
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subttl emdecode.asm - Instruction decoding
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;***
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;emdecode.asm - Instruction decoding
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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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; Instruction decoding.
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; Further decoding of instructions done here.
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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 DECODE
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even
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pub eFLDsdri
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MOV BX,CX ; Dispatch on MF
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AND ebx,6H
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ifdef i386
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JMP FLDsdriTab[2*ebx]
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else
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JMP FLDsdriTab[ebx]
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endif
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pub eFSTsdri
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MOV BX,CX ; Dispatch on MF
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AND ebx,6H
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ifdef i386
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JMP FSTsdriTab[2*ebx]
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else
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JMP FSTsdriTab[ebx]
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endif
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even
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pub eFSTPsdri
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mov bx, cx ; Dispatch on MF
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and ebx, 6h
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ifdef i386
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call FSTsdriTab[2*ebx]
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else
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call FSTsdriTab[ebx]
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endif
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mov esi, [CURstk]
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cmp esi, [BASstk] ; Do we have an empty stack?
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jbe short FSTPSTUnder ; Yes, Underflow.
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FSTPSTOk:
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sub esi, Reg87Len ; decrement SI to previous register
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mov [CURstk], esi ; set current top of stack
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ret
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FSTPSTUnder:
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call UnderStk ; stack underflow error
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jmp FSTPSTOk
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pub eFLDtempORcw
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MOV BX,CX ; Dispatch on MF
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AND ebx,6H
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ifdef i386
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JMP FLDtempORcwTab[2*ebx]
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else
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JMP FLDtempORcwTab[ebx]
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endif
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pub eFSTtempORcw
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MOV BX,CX ; Dispatch on MF
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AND ebx,6H
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ifdef i386
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JMP FSTtempORcwTab[2*ebx]
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else
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JMP FSTtempORcwTab[ebx]
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endif
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pub eFLDregOrFFREE ; We only emulate FLD ST (Duplicate TOS)
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;CX = |Op|r/m|MOD|esc|MF|Arith|
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test cx,06h ; test MF. MF=01 is FFREE, MF=00 is FLD ST(i)
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jnz short jmpeFFREE ; go emulate FFREE
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jmp eFLDreg ; emulate FLD ST(i)
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jmpeFFREE:
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jmp eFFREE ; emulate FFREE ST(i)
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pub eMISCELANEOUS ; We only emulate FCHS, FABS, FTST, & FXAM
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; FCLEX is emulated in non-IBM version
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TEST CX,0806H ; We already have match on Op,MOD,&Arith
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jz short MFzero ; MF = 0, must be FCHS, FABS, FTST or FXAM
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; check for FCLEX (cx = 8B03)
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xor cx,00203h ; toggle low bit of MF and middle bit of r/m
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test cx,00603h ; test for zero in MF and r/m fields
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jnz short jnzUNUSED ; MF <> 01 and/or r/m <> 010 => unemulated
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cmp cx,8104h ; check for FSTSW AX
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je short eFSTSWAX ; yes
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mov [StatusWord],0 ; FCLEX: clear status word
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ret
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pub eFSTSWAX
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ifdef XENIX
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xor eax,eax ; UNDONE - set to non-zero - cleanup code
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else
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push sp ; test for 286 !!!
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pop ax
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cmp ax,sp
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endif
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pub jnzUNUSED
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jnz UNUSED ; UNUSED if not 286
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mov ax,[StatusWord] ; FSTSW AX: save status word in AX
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mov [ebp].regAX,ax ; overwrite AX stack entry
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ret
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MFzero:
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TEST CX,1000H
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JZ short FABSorFCHS
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TEST CX,0400H ; r/m = 101 for FXAM
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JNZ short JMPeFXAM ; r/m = 100 for FTST
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JMP eFTST
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pub JMPeFXAM
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JMP eFXAM
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pub FABSorFCHS
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TEST CX,0400H ; r/m = 001 for FABS
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JNZ short JMPeFABS ; r/m = 000 for FCHS
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JMP eFCHS
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pub JMPeFABS
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JMP eFABS
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pub eFLDconstants
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MOV BL,CH ; Mov r/m field to BX for jump
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SHR BL,1
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AND ebx,0EH
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ifdef i386
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JMP FLDconstantsTab[2*ebx]
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else
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JMP FLDconstantsTab[ebx]
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endif
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pub eTranscendental
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MOV BL,CH ; Mov r/m field to BX for jump
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SHR BL,1
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AND ebx,0EH
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ifdef i386
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JMP TranscendentalTab[2*ebx]
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else
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JMP TranscendentalTab[ebx]
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endif
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pub eVARIOUS
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MOV BL,CH ; Mov r/m field to BX for jump
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SHR BL,1
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AND ebx,0EH
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ifdef i386
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JMP VariousTab[2*ebx]
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else
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JMP VariousTab[ebx]
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endif
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pub eFXCHGreg ; only valid FXCHG is with r/m = 001, MF = 00
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TEST CX,06h ; only valid FXCHG is with MF = 0
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JNZ short UNUSED ; unemulated
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JMP eFXCHG ; emulate FXCH ST(i)
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pub eFSTPreg
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xor cl,04h ; test for MF = 10, valid encoding of FSTP ST(x)
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test cx,06h
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jne short UNUSED ; MF <> 10, no such instruction
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mov ax,1 ; indicate stack should be popped after xfer
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jmp eFST_Preg ; emulate FSTP ST(x)
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;*** eFSTreg - decode FST ST(i),FNOP
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;
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; ARGUMENTS
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; CX = |Op|r/m|MOD|esc|MF|Arith|
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;
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; DESCRIPTION
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; All parts of the instruction except MF and r/m have already
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; been decoded. If MF=0, the instruction is FNOP, which is
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; unemulated. Otherwise, clear AX to indicate FST ST(i), then
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; jump to eFST_Preg, the common emulator routine for
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; FST ST(i) and FSTP ST(i).
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;
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eFSTreg:
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test cl,06h ;test for MF = 0
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jz short UNUSED ;MF=0 ==> FNOP, which is unemulated
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;otherwise this is FST ST(i)
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xor ax,ax ;clear ax to indicate FST ST(i), not FSTP ST(i)
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jmp eFST_Preg ; emulate FSTP ST(x)
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; This sets the error flag indicating Unemulated functions
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eFXTRACT:
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eFDECSTP:
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eFINCSTP:
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ifdef frontend ; unused instructions for frontend version
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eFLDL2T:
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eFLDL2E:
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eFLDPI:
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eFLDLG2:
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eFLDLN2:
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eFPREM:
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eF2XM1:
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eFYL2X:
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eFPTAN:
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eFPATAN:
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eFYL2XP1:
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eFSQRT:
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endif ;frontend
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ifdef SMALL_EMULATOR
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eFLDL2T:
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eFLDL2E:
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eFLDPI:
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eFLDLG2:
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eFLDLN2:
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eFPREM:
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eF2XM1:
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eFYL2X:
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eFPTAN:
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eFPATAN:
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eFYL2XP1:
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eFSQRT:
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endif ;SMALL_EMULATOR
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pub UNUSED
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OR [CURerr],Unemulated
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RET
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ProfEnd DECODE
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