subttl emfcom.asm - Comparison Instructions
page
;*******************************************************************************
;emfcom.asm - Comparison Instructions
;
; Microsoft Confidential
;
; Copyright (c) Microsoft Corporation 1991
; All Rights Reserved
;
;Purpose:
; FCOM,FCOMP,FCOMPP,FUCOM,FUCOMP,FUCOMPP,FTST,FXAM instructions
;
;Revision History:
;
; [] 09/05/91 TP Initial 32-bit version.
;
;*******************************************************************************
;*******************************************************************************
;Dispatch table for compare
;
;One operand has been loaded into ecx:ebx:esi ("source"), the other is
;pointed to by edi ("dest").
;
;Tag of source is shifted. Tag values are as follows:
.erre TAG_SNGL eq 0 ;SINGLE: low 32 bits are zero
.erre TAG_VALID eq 1
.erre TAG_ZERO eq 2
.erre TAG_SPCL eq 3 ;NAN, Infinity, Denormal, Empty
;Any special case routines not found in this file are in emarith.asm
tFcomDisp label dword ;Source (reg) Dest (*[di] = ST)
dd ComDouble ;single single
dd ComDouble ;single double
dd ComDestZero ;single zero
dd ComSpclDest ;single special
dd ComDouble ;double single
dd ComDouble ;double double
dd ComDestZero ;double zero
dd ComSpclDest ;double special
dd ComSrcZero ;zero single
dd ComSrcZero ;zero double
dd ComEqual ;zero zero
dd ComSpclDest ;zero special
dd ComSpclSource ;special single
dd ComSpclSource ;special double
dd ComSpclSource ;special zero
dd ComBothSpcl ;special special
EM_ENTRY eFICOMP16
eFICOMP16:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset PopWhenDone
push offset ComOpLoaded
jmp Load16Int ;Returns to ComOpLoaded
EM_ENTRY eFICOM16
eFICOM16:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset ComOpLoaded
jmp Load16Int ;Returns to ComOpLoaded
EM_ENTRY eFICOMP32
eFICOMP32:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset PopWhenDone
push offset ComOpLoaded
jmp Load32Int ;Returns to ComOpLoaded
EM_ENTRY eFICOM32
eFICOM32:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset ComOpLoaded
jmp Load32Int ;Returns to ComOpLoaded
EM_ENTRY eFCOMP32
eFCOMP32:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset PopWhenDone
push offset ComOpLoaded
jmp Load32Real ;Returns to ComOpLoaded
EM_ENTRY eFCOM32
eFCOM32:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset ComOpLoaded
jmp Load32Real ;Returns to ComOpLoaded
EM_ENTRY eFCOMP64
eFCOMP64:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset PopWhenDone
push offset ComOpLoaded
jmp Load64Real ;Returns to ComOpLoaded
EM_ENTRY eFCOM64
eFCOM64:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset ComOpLoaded
jmp Load64Real ;Returns to ComOpLoaded
EM_ENTRY eFUCOMPP
eFUCOMPP:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset ComPop2
jmp eFUCOM0
EM_ENTRY eFUCOMP
eFUCOMP:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset PopWhenDone
jmp eFUCOM0
EM_ENTRY eFUCOM
eFUCOM:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
eFUCOM0:
;esi = pointer to st(i) from instruction field
;edi = [CURstk]
mov ecx,EMSEG:[esi].ExpSgn
mov ebx,EMSEG:[esi].lManHi
mov esi,EMSEG:[esi].lManLo
mov dl,40H ;Flag FUCOM - Look for SNAN
jmp UComOpLoaded
EM_ENTRY eFCOMPP
eFCOMPP:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset ComPop2
jmp eFCOM0
EM_ENTRY eFCOMP
eFCOMP:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
push offset PopWhenDone
jmp eFCOM0
EM_ENTRY eFCOM
eFCOM:
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
eFCOM0:
;esi = pointer to st(i) from instruction field
;edi = [CURstk]
mov ecx,EMSEG:[esi].ExpSgn
mov ebx,EMSEG:[esi].lManHi
mov esi,EMSEG:[esi].lManLo
ComOpLoaded:
; mov EMSEG:[UpdateCCodes],1
mov dl,0 ;flag FCOM - Look for any NAN
UComOpLoaded:
mov ebp,offset tFcomDisp
mov al,cl
mov ah,EMSEG:[edi].bTag
test ax,ZEROorSPCL * 100H + ZEROorSPCL
jnz TwoOpDispatch
;.erre ComDouble eq $ ;Fall into ComDouble
;*********
ComDouble:
;*********
;
;ebx:esi = op1 mantissa
;ecx = op1 sign in bit 15, exponent in high half
;edi = pointer to op2
mov eax,EMSEG:[edi].ExpSgn
and ax,bSign shl 8 ;Keep sign only
and cx,bSign shl 8
cmp ah,ch ;Are signs the same?
jnz StBigger
cmp eax,ecx ;Are exponents the same?
jl StSmaller
jg StBigger
cmp EMSEG:[edi].lManHi,ebx ;Compare mantissas
jnz MantDif
cmp EMSEG:[edi].lManLo,esi ;Set flags for ST - src
jz ComEqual
MantDif:
adc al,al ;Copy CY flag to bit 0
rol ah,1 ;Rotate sign to bit 0
xor al,ah ;Flip saved CY bit if negative
mov EMSEG:[SWcc],al ;Set condition code
ret
StSmaller:
not ah
StBigger:
;ah = sign of ST
;ch = sign of other operand
;ST is bigger if it is positive (smaller if it is negative).
;Use the sign bit directly as the "less than" bit C0.
.erre C0 eq 1
shr ah,7 ;Bring sign down to bit 0, clear CY
mov EMSEG:[SWcc],ah ;Bit set if ST smaller (negative)
ret
ComEqual:
mov EMSEG:[SWcc],CCequal
ret
PopWhenDone:
.erre bTAG_NOPOP eq -1
inc cl ;OK to pop?
jz ComPopX ;No - had unmasked Invalid Operation
POPSTret
ComPop2:
.erre bTAG_NOPOP eq -1
inc cl ;OK to pop?
jz ComPopX ;No - had unmasked Invalid Operation
mov esi,EMSEG:[CURstk]
mov EMSEG:[esi].bTag,bTAG_EMPTY
add esi,Reg87Len*2
cmp esi,ENDstk ;JWM
je PopOneOver
ja PopTwoOver
mov EMSEG:[esi-Reg87Len].bTag,bTAG_EMPTY
mov EMSEG:[CURstk],esi
ComPopX:
ret
PopOneOver:
mov EMSEG:[CURstk],BEGstk ;JWM
ifdef NT386
mov EMSEG:[INITstk].bTAG,bTAG_EMPTY
else
mov EMSEG:[XINITstk].bTAG,bTAG_EMPTY
endif
ret
PopTwoOver:
mov EMSEG:[CURstk],BEGstk+Reg87Len ;JWM
ifdef NT386
mov EMSEG:[BEGstk].bTAG,bTAG_EMPTY
else
mov EMSEG:[XBEGstk].bTAG,bTAG_EMPTY
endif
ret
;*******************************************************************************
;Special cases for FCOM/FUCOM.
;These don't share with those in emarith.asm because NANs are treated
;differently.
ComDestZero:
;ST is zero, so Src is bigger if it is positive (smaller if it is negative).
;Use the sign bit directly as the "less than" bit C0.
not ch ;C0 is 1 if ST < Src
.erre C0 eq 1
shr ch,7 ;Bring sign down to bit 0
mov EMSEG:[SWcc],ch ;Bit set if Src smaller (negative)
ret
ComSrcZero:
;ST is bigger if it is positive (smaller if it is negative).
;Use the sign bit directly as the "less than" bit C0.
mov al,EMSEG:[edi].bSgn
.erre C0 eq 1
shr al,7 ;Bring sign down to bit 0
mov EMSEG:[SWcc],al ;Bit set if ST smaller (negative)
ret
ComSpclSource:
cmp cl,bTAG_NAN
jz ComSrcNAN
cmp cl,bTAG_INF
jz ComDestZero
cmp cl,bTAG_DEN
jz ComDenormal
;Must be empty
ComEmpty:
mov EMSEG:[CURerr],Invalid+StackFlag
jmp ComChkMask
ComSrcNAN:
shl edx,24 ;Move dl to high byte
test ebx,edx ;See if we report error with this NAN
ComChkNAN:
jnz Incomp
ComInvalid:
mov EMSEG:[CURerr],Invalid ;Flag the error
ComChkMask:
test EMSEG:[CWmask],Invalid ;Is exception masked?
jnz Incomp
mov cl,bTAG_NOPOP ;Unmasked, don't pop stack
Incomp:
mov EMSEG:[SWcc],CCincomprable
ret
ComSpclDest:
mov al,EMSEG:[edi].bTag
cmp al,bTAG_INF
jz ComSrcZero
cmp al,bTAG_Empty
jz ComEmpty
cmp al,bTAG_DEN
jz ComDenormal
;Must be NAN
ComDestNAN:
test EMSEG:[edi].bMan7,dl ;See if we report error with this NAN
jmp ComChkNAN
ComBothSpcl:
mov al,EMSEG:[edi].bTag
cmp cl,bTAG_EMPTY
jz ComEmpty
cmp al,bTAG_EMPTY
jz ComEmpty
cmp cl,bTAG_NAN
jz ComSrcNAN
cmp al,bTAG_NAN
jz ComDestNAN
mov ah,cl
cmp ax,(bTAG_INF shl 8) + bTag_INF ;Are both Infinity?
jz ComDouble ;If so, compare their signs
;Must have at least one denormal
ComDenormal:
or EMSEG:[CURerr],Denormal
jmp ComDouble
;*******************************************************************************
XAM_Unsupported equ 0
XAM_NAN equ C0
XAM_Norm equ C2
XAM_Inf equ C2+C0
XAM_Zero equ C3
XAM_Empty equ C3+C0
XAM_Den equ C3+C2
tXamTag label byte
.erre TAG_SNGL eq $-tXamTag
db XAM_Norm ;TAG_SNGL
.erre TAG_VALID eq $-tXamTag
db XAM_Norm ;TAG_VALID
.erre TAG_ZERO eq $-tXamTag
db XAM_Zero ;TAG_ZERO
.erre TAG_EMPTY eq $-tXamTag
db XAM_Empty ;TAG_EMPTY
db 0
db 0
db 0
.erre TAG_INF eq $-tXamTag
db XAM_Inf ;TAG_INF
db 0
db 0
db 0
.erre TAG_NAN eq $-tXamTag
db XAM_NAN ;TAG_NAN
db 0
db 0
db 0
.erre TAG_DEN eq $-tXamTag
db XAM_Den ;TAG_DEN
EM_ENTRY eFXAM
eFXAM:
;edi = [CURstk]
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
mov eax,EMSEG:[edi].ExpSgn ;Get sign and tag
mov bl,ah ;Save sign
and bl,bSign ;Keep only sign bit
and eax,0FH ;Save low 4 bits of tag
mov al,tXamTag[eax] ;Lookup cond. codes for this tag
.erre C1 eq 2 ;Bit 1
.erre bSign eq 80H ;Bit 7
shr bl,7-1 ;Move sign bit to CC C1
or al,bl
mov EMSEG:[SWcc],al
ret
;*******************************************************************************
EM_ENTRY eFTST
eFTST:
;edi = [CURstk]
and [esp].[OldLongStatus+4],NOT(ConditionCode SHL 16) ;clear C0,C1,C2,C3
mov eax,EMSEG:[edi].ExpSgn
cmp al,bTAG_ZERO
jz ComEqual
ja TestSpcl
;Either single or double, non-zero. Just check sign.
TestSign:
shr ah,7 ;Bring sign down to bit 0
mov EMSEG:[SWcc],ah ;Bit set if negative
ret
TestSpcl:
cmp al,bTAG_INF
jz TestSign ;Normal test for Infinity
cmp al,bTAG_EMPTY
jz ComEmpty
cmp al,bTAG_NAN
jz ComInvalid
;Must be denormal
mov EMSEG:[CURerr],Denormal
jmp TestSign