hw/i386.reference/LEAVE.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode LEAVE</TITLE>
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   7 <B>up:</B> <A HREF="c17.htm">
   8 Chapter 17 -- 80386 Instruction Set</A><BR>
   9 <B>prev:</B><A HREF="LEA.htm"> LEA Load Effective Address</A><BR>
  10 <B>next:</B><A HREF="LGDT.htm"> LGDT/LIDT Load Global/Interrupt Descriptor Table Register</A>
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  13 <P>
  14 <H1>LEAVE -- High Level Procedure Exit</H1>
  15
  16 <PRE>
  17 Opcode  Instruction  Clocks  Description
  18
  19 C9      LEAVE        4       Set SP to BP, then pop BP
  20 C9      LEAVE        4       Set ESP to EBP, then pop EBP
  21 </PRE>
  22
  23 <H2>Operation</H2>
  24
  25 <PRE>
  26 IF StackAddrSize = 16
  27 THEN
  28    SP := BP;
  29 ELSE (* StackAddrSize = 32 *)
  30    ESP := EBP;
  31 FI;
  32 IF OperandSize = 16
  33 THEN
  34    BP := Pop();
  35 ELSE (* OperandSize = 32 *)
  36    EBP := Pop();
  37 FI;
  38 </PRE>
  39
  40 <H2>Description</H2>
  41
  42 LEAVE reverses the actions of the
  43 <A HREF="ENTER.htm">ENTER</A> instruction. By copying the
  44 frame pointer to the stack pointer, LEAVE releases the stack space used
  45 by a procedure for its local variables. The old frame pointer is popped
  46 into BP or EBP, restoring the caller's frame. A subsequent
  47 <A HREF="RET.htm">RET</A>
  48 instruction removes any arguments pushed onto the stack of the exiting
  49 procedure.
  50
  51 <H2>Flags Affected</H2>
  52
  53 None
  54
  55 <H2>Protected Mode Exceptions</H2>
  56
  57 #SS(0) if BP does not point to a location within the limits of the current
  58 stack segment
  59
  60 <H2>Real Address Mode Exceptions</H2>
  61
  62 Interrupt 13 if any part of the operand would lie outside of the effective
  63 address space from 0 to 0FFFFH
  64
  65 <H2>Virtual 8086 Mode Exceptions</H2>
  66
  67 Same exceptions as in Real Address Mode
  68
  69
  70 <P>
  71 <HR>
  72 <P>
  73 <B>up:</B> <A HREF="c17.htm">
  74 Chapter 17 -- 80386 Instruction Set</A><BR>
  75 <B>prev:</B><A HREF="LEA.htm"> LEA Load Effective Address</A><BR>
  76 <B>next:</B><A HREF="LGDT.htm"> LGDT/LIDT Load Global/Interrupt Descriptor Table Register</A>
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