334 lines
7.4 KiB
NASM
334 lines
7.4 KiB
NASM
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page ,132
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subttl emlssng.asm - Load/Store Single Precision Numbers
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;***
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;emlssng.asm - Load/Store Single Precision Numbers
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;
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; Copyright (c) 1984-89, Microsoft Corporation
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;
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;Purpose:
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; Load/Store Single Precision Numbers
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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 LSSNG
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;*********************************************************************;
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; ;
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; Load Single Real ;
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; ;
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;*********************************************************************;
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;
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; Subroutine converts single in regs to internal at ES:SI
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pub eFLDsr
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LDUS2AX ; get lower mantissa part
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MOV DI,AX ; 2 keep lower mantissa in DX
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LDUS2AX ; get upper exponent/sign part
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MOV DL,AL ; 2 copy most sig. mantissa byte
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ROL AX,1 ; 2 sign to AL, exponent to AH
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AND AL,1 ; 4 clear all flags except sign
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ROR AL,1 ; 2 get sign in right position
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XCHG AL,AH
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; AX, DI, DL: operand one
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PUSHST ; 64 allocate another register
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pub SingleToInternal
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OR DL,80H ; Set leading bit of mantissa
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XOR DH,DH ; Set Tag to valid non-zero
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CMP AL,SexpMax ; Is Number NAN or Inf?
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JE short SNANorInf
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if fastSP
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OR AH,Single ; Set single Precision flag
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endif
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CMP AL,SexpMin ; Is Number Zero or Denormal
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JE short SZeroOrDenorm
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; Otherwise number is valid non-zero
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MOV Flag[esi],AH ; Store sign
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SUB AL,SexpBias ; Unbias the exponent
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CBW
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pub SStoreExpnTag
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MOV Expon[esi],AX ; Store Exponent
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MOV Tag[esi],DH ; Store Tag
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MOV MB7[esi],DL ; Store Mantissa
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MOV MB5[esi],DI
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ife fastSP
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XOR AX,AX ; Clear low order bytes of Mantissa
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MOV MB4[esi],AL
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MOV MB2[esi],AX
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MOV MB0[esi],AX
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endif
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RET
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pub SNANorInf
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MOV Flag[esi],AH ; Store sign
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MOV AX,IexpMax - IexpBias ; Set exponent to internal max
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MOV DH,Special ; Set Tag to show NAN or Inf
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CMP DL,80H ; If anything other than leading bit
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JNE short SStoreExpnTag ; is set number is NAN (not Inf)
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OR DI,DI
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JNE short SStoreExpnTag
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OR DH,ZROorINF ; Set Tag to show Inf
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JMP SStoreExpnTag
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pub SZeroorDenorm
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MOV Flag[esi],AH ; Store sign
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CMP DL,80H ; If anything other than leading bit
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JNE short SDenormal ; is set number is Denormal
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OR DI,DI
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JNE short SDenormal
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MOV AX,IexpMin - IexpBias ; Set exponent to internal min
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OR DH,ZROorINF ; Set Tag to show 0
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JMP SStoreExpnTag
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pub SDenormal
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OR [CURerr],Denormal ; Set Denormal Exception
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SUB AL,SexpBias ; unbias the Exponent
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CBW
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INC AX
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pub SNormalize
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DEC AX
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SHL DI,1
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RCL DL,1
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OR DL,DL
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JNS SNormalize
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JMP SStoreExpnTag
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page
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;************************************************************;
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; ;
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; Store Single Real ;
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; ;
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;************************************************************;
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pub SSpecial ; number is NAN or INF or Zero
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TEST CL,Special ; NAN or INF?
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JNE short SSNANorINF
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XOR AX,AX ; Number is Zero
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MOV BX,AX
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JMP STRUNC
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pub SSNANorINF
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TEST CL,ZROorINF
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JNE short SInf
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MOV BX,MB5[esi] ; Number is a NAN
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MOV AL,MB7[esi]
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MOV AH,Flag[esi] ; Pick up Sign
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SHL AX,1 ; Destroy leading bit, Sign to CF
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MOV AH,SexpMax
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RCR AX,1
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JMP STRUNC
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pub SInf
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MOV AH,Flag[esi]
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JMP SSignedInfinity
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pub JMPSOver
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JMP SOver
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pub JMPSUnder
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JMP SUnder
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; ES:SI: memory address of single
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; stores and misc. operations; first setup register values as follows:
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; AX: TOS flags (for DOUB and SIGN flags)
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; SI: TOS address (offset)
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pub eFSTsr
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mov edi,esi ; ES:DI = store address
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MOV esi,[CURstk] ; 14 load TOS address
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MOV AX,Flag[esi] ; 21 get TOS flags (sign, double)
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; convert internal at DS:SI to single
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; DS:SI = TOS, ES:DI = memory, CH = operation (POP), BP = old ES value
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MOV CL,Tag[esi] ; See if number is NAN or Inf or Zero
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OR CL,CL
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JNZ short SSpecial
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MOV CL,Flag[esi] ; Pick up sign & single precision flag
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MOV AX,Expon[esi]
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CMP AX,SexpMax - SexpBias
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JGE short JMPSOver
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CMP AX,SexpMin - SexpBias
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JLE short JMPSUnder
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ADD AL,SexpBias ; Bias the Exponent
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MOV AH,MB7[esi] ; Pick up MSB of Mantissa
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XCHG AH,AL
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SHL AL,1 ; Shift mantissa to destroy leading integer bit
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SHL CL,1 ; Get sign into CF
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RCR AX,1 ; Pack sign, exp, & MSB
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if fastSP
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TEST CL,Single*2 ; if number was single rounding is not needed
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JZ SS1
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MOV BX,MB5[esi]
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JMP SHORT STRUNC
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SS1:
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endif
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MOV DX,MB0[esi] ; DL Will be the sticky bit
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OR DX,MB2[esi] ; DH will be round and the rest of sticky
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OR DL,DH
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XOR DH,DH
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MOV BX,MB5[esi]
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OR DX,MB3[esi]
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JZ short STRUNC ; If no Round or Sticky result is exact
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OR [CURerr],Precision
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pub SRound ; single in AX:BX:DX
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MOV CL,[CWcntl] ; Need to know Rounding Control
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SHR CL,1
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SHR CL,1
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SHR CL,1
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JC short StDOWNorCHOP24
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SHR CL,1
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JC short StUP24
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pub StNEAR24
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CMP DX,8000H ; How are round and sticky bits?
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JB short STRUNC ; No round, so truncate
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JA short SINC ; Round and sticky so round up
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TEST BL,1 ; Round and no sticky, is last bit even?
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JZ short STRUNC ; Yes, so truncate.
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pub SINC
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MOV DL,AL ; Increment mantissa
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ADD BX,1
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ADC AX,0
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XOR DL,AL ; See if we overflowed a bit into the exponent
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JNS short STRUNC ; If not number is now correct so go store
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MOV DX,AX ; Exponent was incremented, see if it overflowed
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SHL DX,1
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CMP DH,SexpMax
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JE short SOver
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pub StCHOP24
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STRUNC:
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XCHG AX,BX
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STAX2US
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MOV AX,BX
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STAX2US
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pub SStoreExit
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RET
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pub StDOWNorCHOP24
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SHR CL,1
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JC short StCHOP24
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pub StDOWN24
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OR AH,AH ; Test the sign
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JS short SINC
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JMP short STRUNC
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pub StUP24
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OR AH,AH ; Test the sign
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JS short STRUNC
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JMP short SINC
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pub SOver ; Number overflowed Single Precision range.
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; Result returned depends upon rounding control
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OR [CURerr],Overflow + Precision
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MOV CL,[CWcntl]
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SHR CL,1
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SHR CL,1
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SHR CL,1
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JC short StMOvDNorCHP24
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SHR CL,1
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JC short StMOvUP24
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StMOvNEAR24: ; Masked Overflow Near Rounding
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pub SSignedInfinity ; Return signed infinity
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MOV BX,[IEEEinfinityS + 2]
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AND AH,Sign ; Overstore the proper sign
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OR BH,AH
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MOV AX,[IEEEinfinityS]
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STAX2US
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MOV AX,BX
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STAX2US
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JMP SStoreExit
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pub StMOvDNorCHP24
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SHR CL,1
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JC short StMOvCHOP24
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pub StMOvDOWN24 ; Masked Overflow Down Rounding
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TEST AH,Sign ; Positive goes to biggest
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JNZ short SSignedInfinity
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StMOvCHOP24: ; Masked Overflow Chop Rounding
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pub SSignedBiggest
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MOV BX,[IEEEbiggestS + 2]
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AND AH,Sign ; Overstore the proper sign
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OR AH,BH
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MOV AL,BL
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STAX2US
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MOV AX,[IEEEbiggestS]
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STAX2US
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JMP SStoreExit
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pub StMOvUP24 ; Masked Overflow Up Rounding
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TEST AH,Sign ; Negative goes to biggest
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JZ short SSignedInfinity
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JMP SSignedBiggest
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pub SUnder ; Masked Underflow - Try to denormalize
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OR [CURerr],Underflow+Precision
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NEG AX ; Convert exponent (which is too small)
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ADD AX,SexpMin-SexpBias+1 ; To a positive shift count
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CMP AX,24 ; Is shift more than mantissa precision
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JGE short Szero
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XCHG CX,AX
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ifdef i386
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movzx ecx,cx ; (ecx) = zero-extended loop count
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endif
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MOV DX,MB0[esi] ; Pick up Insignif bytes for sticky bit
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OR DX,MB2[esi]
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MOV AL,DL
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OR AL,DH
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MOV DX,MB4[esi]
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MOV BX,MB6[esi]
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OR AL,AL
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JZ short SSHIFTR
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OR DL,1 ; Set the sticky bit
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pub SSHIFTR
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SHR BX,1
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RCR DX,1
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JNC short SSLOOP
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OR DL,1
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pub SSLOOP
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LOOP SSHIFTR
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XCHG AH,CH ; Restore operation to CH
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MOV AH,Flag[esi] ; Pick up sign
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AND AH,Sign ; Mask to sign only
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MOV AL,BH ; Biased exponent for a denormal is 0
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MOV BH,BL
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MOV BL,DH
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MOV DH,DL
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XOR DL,DL
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JMP SRound
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pub Szero
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XOR AX,AX
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MOV BX,AX
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JMP STRUNC ; Go store single and exit
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ProfEnd LSSNG
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