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page ,132 subttl emstack.asm - Emulator Stack Management Area;***;emstack.asm - Emulator Stack Management Area;; Copyright (c) 1986-89, Microsoft Corporation;;Purpose:; Emulator Stack Management Area;; This Module contains Proprietary Information of Microsoft; Corporation and should be treated as Confidential.;;Revision History:; See emulator.hst;;*******************************************************************************
ProfBegin STACK
;*********************************************************************;; ;; Emulator Stack Management Area ;; ;;*********************************************************************;
; The emulator maintains an "finite" stack of 12 byte registers.
; Stand-alone emulator has 1 chunk only.
; This is done using a list of finite length stack chunks, each of; which has the following format:; +00 first (deepest) 12 byte register; +12 next 12 byte register; (and so on through last possible register)
; MACROS used to manipulate the emulator/8087 memory stack
; This macro allocates a new TOS register, returns SI with its address.
PUSHST MACRO local pushstok mov esi,[CURstk] ; 14 get address of current register cmp esi,[LIMstk] ; 15 is current register end of stack jne short pushstok ; 16 no, still room in stack call OverStk ; stack overflow errorpushstok: add esi,Reg87Len ; 4 increment SI to next free register mov [CURstk],esi ; 15 set current top of stack ENDM ; 64 total
; This macro deallocates TOS register, returns SI with new TOS address.; Note: assumes SI contains TOS address, CURstk; BASstk converted back to a variable to enable macro use for 8087 stack; handling. Brad Verheiden, 4-13-84.
POPSTsi MACRO local popstok cmp esi,[BASstk] ; 15 was it last register in the chunk ? jnz short popstok ; 16 no, still room in current chunk call UnderStk ; stack underflow errorpopstok: sub esi,Reg87Len ; 4 decrement SI to previous register mov [CURstk],esi ; 15 set current top of stack ENDM ; 64 total
POPST MACRO mov esi,[CURstk] POPSTsi ENDM
ChangeDIfromTOStoNOS MACRO sub edi,Reg87Len ENDM
page; This area contains two procedures, OverStk and UnderStk,; which generate a stack overflow error.
; OverStk: invoked within PUSHST macro; on entry, the stack is full; on return, SI contains address of base of stack
; UnderStk: invoked within POPST macro; on entry, the stack is empty; on return, SI contains address of base of stack
pub OverStk OR byte ptr [CURerr+1],StackOverflow/256 ; raise stack overflow CMP [Have8087],0 ; Is 8087 present JZ short OverStkEnd ; No - don't touch AX OR AH,StackOverflow/256 ; Indicate memory overflow for 8087
pub OverStkEnd RET ; finished
pub UnderStk OR byte ptr [CURerr+1],StackUnderflow/256 ; raise stack underflow RET ; finished
ProfEnd STACK
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