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page ,132 subttl emnew - emulator new instruction support;***;emnew.asm - emulator new instruction support;; Copyright (c) 1985-89, Microsoft Corporation;;Purpose:; Emulator new instruction support;; This Module contains Proprietary Information of Microsoft; Corporation and should be treated as Confidential.;;Revision History:; See emulator.hst;;*******************************************************************************
ProfBegin NEW
;*** eFFREE - emulate FFREE ST(i);; ARGUMENTS; CX = |Op|r/m|MOD|esc|MF|Arith|; r/m is register to free;; DESCRIPTION; This routine assumes that the register being freed is; either at the top or the bottom of the floating point; stack. This is consistent with its use by the cmerge; compiler. If ST(i) is valid, all registers from ST(0); to ST(i-1) are moved down one position in the stack,; eliminating ST(i). [CURstk] is moved to the new location; of ST(0).;; REGISTERS; modifies si,di,dx
pub eFFREE call RegAddr ; di <== address of ST(i) ; carry set if invalid register jnc short validSTi ; ok, continue pop edx ; toss return address jmp InvalidOperand ; set stack underflow/invalid and exit
validSTi: mov esi,edi ; si <== address of ST(i)MovLoop: add esi,Reg87Len ; si <== address of ST(i-1) cmp esi,[CURstk] ; source addr <= top of stack? jg short SetCURstk ; set [CURstk] and exit call MOVRQQ ; ST(j) <== ST(j-1) add edi,Reg87Len ; move dest ptr to next stack entry jmp short MovLoop ; continue moving register entries
SetCURstk: sub edi,Reg87Len ; di points to new location of ST(0) mov [CURstk],edi ; set new top of stack ptr ret
;*** eFXCHG - emulate FXCH ST(i);; ARGUMENTS; CX = |Op|r/m|MOD|esc|MF|Arith|; r/m is the source register;; DESCRIPTION; exchange ST(i) and ST(0) as follows:; temp <== ST(0); ST(0) <== ST(i); ST(i) <== temp; indicate stack underflow error if ST(i) does not exist;; REGISTERS; modifies ax,es,si,di,dx,cx,bx
pub eFXCHG test cx,01c00h ;test for ST(i) == ST(0) jz short fxchRet ;fxch ST(0),ST(0) is a nop mov ax,ds mov es,ax ;set es == ds call RegAddr ;di points to ST(i), si points to ST(0) ;carry set if invalid register jnc short okReg ;ok, continue pop edx ; toss return address jmp InvalidOperand ;give stack underflow/invalid error
okReg: mov ecx,6 ;loop counterWordSwap: ;exchange a word of ST(0) and ST(i) mov ax,[esi] ;ax <== [si] mov bx,[edi] ;bx <== [di] stos word ptr es:[edi] ;[(di++)] <== ax mov [esi],bx ;[si] <== bx inc esi inc esi ;si++ loop WordSwap ;exchange the six words of ST(0), ST(i)fxchRet: ret
;*** eFLDreg - emulate FLD ST(i);; ARGUMENTS; CX = |Op|r/m|MOD|esc|MF|Arith|; r/m is the source register;; DESCRIPTION; allocate new ST(0) and copy ST(i) into it; indicate stack underflow error if ST(i) does not exist;; REGISTERS; modifies ax,di,si
pub eFLDreg call RegAddr ;di <== address of ST(i), si points to ST(0) ;carry set if invalid register jnc short okSTi ;yes, continue pop edx ; toss return address jmp InvalidOperand ;stack underflow, invalid operation
okSTi: PUSHST ;allocate new TOS mov ax,ds mov es,ax ;set ES == DS xchg esi,edi ;si = source , di = destination call MOVRQQ ;move ST(i) to new ST(0) ret
;*** eFST_Preg - emulate FST ST(i) and FSTP ST(i);; ARGUMENTS; AX = 0 if FST ST(i); 1 if FSTP ST(i); CX = |Op|r/m|MOD|esc|MF|Arith|; (except bit 2 of cl is toggled); r/m is the source register;; DESCRIPTION; move contents of ST(0) to ST(i). If ax <> 0 pop stack; after transfer.;; REGISTERS; modifies si,di,dx
pub eFST_Preg test cx,01c0h ;test for ST(i) == ST(0) jz short FSTRet ;pop stack and return call RegAddr ;di <== address of ST(i), si points to ST(0) ;carry set if invalid register jnc short ValidReg ;yes, continue pop edx ; toss return address jmp InvalidOperand ;no, indicate stack underflow/invalid
ValidReg: mov dx,ds mov es,dx ;set es == ds call MOVRQQ ;ST(i) <== ST(0)
FSTRet: or ax,ax ;FST ST(i) or FSTP ST(i)? jz short NoPOP ;FST ST(i) - don't pop the stack POPST ;pop the 8087 stackNoPOP: ret
ProfEnd NEW
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