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126 lines
3.4 KiB
126 lines
3.4 KiB
subttl emfconst.asm - Loading of 387 on chip constants
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page
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;*******************************************************************************
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;emfconst.asm - Loading of 387 on chip constants
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;
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; Microsoft Confidential
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;
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; Copyright (c) Microsoft Corporation 1991
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; All Rights Reserved
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;
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;Purpose:
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; FLDZ, FLD1, FLDPI, FLDL2T, FLDL2E, FLDLG2, FLDLN2 instructions
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;Inputs:
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; edi = [CURstk]
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;
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;Revision History:
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;
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; [] 09/05/91 TP Initial 32-bit version.
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;
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;*******************************************************************************
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PrevStackWrap edi,Ld1 ;Tied to PrevStackElem below
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EM_ENTRY eFLD1
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eFLD1:
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;edi = [CURstk]
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PrevStackElem edi,Ld1 ;Point to receiving location
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cmp EMSEG:[edi].bTag,bTAG_EMPTY ;Is it empty?
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jnz FldErr ;in emload.asm
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mov EMSEG:[CURstk],edi
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mov EMSEG:[edi].lManLo,0
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mov EMSEG:[edi].lManHi,1 shl 31
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mov EMSEG:[edi].ExpSgn,bTAG_SNGL ;Exponent and sign are zero
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ret
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PrevStackWrap edi,Ldz ;Tied to PrevStackElem below
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EM_ENTRY eFLDZ
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eFLDZ:
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;edi = [CURstk]
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PrevStackElem edi,Ldz ;Point to receiving location
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cmp EMSEG:[edi].bTag,bTAG_EMPTY ;Is it empty?
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jnz FldErr ;in emload.asm
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mov EMSEG:[CURstk],edi
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mov EMSEG:[edi].lManLo,0
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mov EMSEG:[edi].lManHi,0
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mov EMSEG:[edi].ExpSgn,bTAG_ZERO ;Exponent and sign are zero
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ret
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;*******************************************************************************
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;The 5 irrational constants need to be adjusted according to rounding mode.
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DefConst macro cName,low,high,expon,round
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c&cName&lo equ low
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c&cName&hi equ high
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c&cName&exp equ expon
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c&cName&rnd equ round
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endm
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DefConst FLDL2T,0CD1B8AFEH,0D49A784BH,00001H,0
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DefConst FLDL2E,05C17F0BCH,0B8AA3B29H,00000H,1
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DefConst FLDLG2,0FBCFF799H,09A209A84H,0FFFEH,1
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DefConst FLDLN2,0D1CF79ACH,0B17217F7H,0FFFFH,1
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DefConst FLDPI,02168C235H,0C90FDAA2H,00001H,1
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LoadConstant macro cName,nojmp
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EM_ENTRY e&cName
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e&cName:
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mov ebx,c&cName&hi
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mov edx,c&cName&lo
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mov ecx,c&cName&exp shl 16 + c&cName&rnd
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ifb <nojmp>
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jmp CommonConst
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endif
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endm
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LoadConstant FLDL2T
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LoadConstant FLDL2E
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LoadConstant FLDLG2
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LoadConstant FLDLN2
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LoadConstant FLDPI,nojmp
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CommonConst:
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;ebx:edx = mantissa of constant, rounded to nearest
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;high ecx = exponent
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;ch = sign
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;cl = rounding flag: 1 indicates roundup occured for round nearest, else 0
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;edi = [CURstk]
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test EMSEG:[CWcntl],RoundControl ;Check rounding control bits
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.erre RCnear eq 0
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jnz NotNearConst ;Adjust constant if not round nearest
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StoreConst:
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mov cl,bTAG_VALID
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mov esi,edx
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jmp FldCont ;In emload.asm
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NotNearConst:
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;It is known that the five constants positive irrational numbers.
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;This means they are never exact, and chop and round down always
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;produce the same answer. It is also know that the values are such
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;that rounding only alters bits in the last byte.
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;
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;A flag in cl indicates if the number has been rounded up for round
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;nearest (1 = rounded up, 0 = rounded down). In chop and round down
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;modes, this flag can be directly subtracted to reverse the rounding.
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;In round up mode, we want to add (1-flag) = -(flag-1).
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.erre RCchop eq 0CH ;Two bits set only for chop
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test EMSEG:[CWcntl],RCdown ;DOWN bit set?
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jnz DirectRoundConst ;If so, it's chop or down
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;Round Up mode
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dec cl ;-1 if round up needed, else 0
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DirectRoundConst:
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sub dl,cl ;Directed rounding
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jmp StoreConst
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