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remove redundant memory access from IRET

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This commit is contained in:
Stanislav Shwartsman 2017-04-01 05:49:01 +00:00
parent e023b5896f
commit bad84e48cd
1 changed files with 10 additions and 17 deletions
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27
bochs/cpu/iret.cc
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@ -2,7 +2,7 @@
// $Id$
/////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2005-2012 Stanislav Shwartsman
// Copyright (c) 2005-2017 Stanislav Shwartsman
// Written by Stanislav Shwartsman [sshwarts at sourceforge net]
//
// This library is free software; you can redistribute it and/or
@ -99,7 +99,6 @@ BX_CPU_C::iret_protected(bxInstruction_c *i)
/* NT = 0: INTERRUPT RETURN ON STACK -or STACK_RETURN_TO_V86 */
unsigned top_nbytes_same;
Bit32u new_eip = 0, new_esp, temp_ESP, new_eflags = 0;
Bit16u new_ip = 0, new_flags = 0;
/* 16bit opsize | 32bit opsize
* ==============================
@ -138,9 +137,9 @@ BX_CPU_C::iret_protected(bxInstruction_c *i)
}
}
else {
new_flags = stack_read_word(temp_ESP + 4);
new_eflags = stack_read_word(temp_ESP + 4);
raw_cs_selector = stack_read_word(temp_ESP + 2);
new_ip = stack_read_word(temp_ESP + 0);
new_eip = stack_read_word(temp_ESP + 0);
}
parse_selector(raw_cs_selector, &cs_selector);
@ -166,12 +165,13 @@ BX_CPU_C::iret_protected(bxInstruction_c *i)
check_cs(&cs_descriptor, raw_cs_selector, 0, cs_selector.rpl);
if (cs_selector.rpl == CPL) { /* INTERRUPT RETURN TO SAME LEVEL */
/* load CS-cache with new code segment descriptor */
branch_far32(&cs_selector, &cs_descriptor, new_eip, cs_selector.rpl);
/* top 6/12 bytes on stack must be within limits, else #SS(0) */
/* satisfied above */
if (i->os32L()) {
/* load CS-cache with new code segment descriptor */
branch_far32(&cs_selector, &cs_descriptor, new_eip, cs_selector.rpl);
// ID,VIP,VIF,AC,VM,RF,x,NT,IOPL,OF,DF,IF,TF,SF,ZF,x,AF,x,PF,x,CF
Bit32u changeMask = EFlagsOSZAPCMask | EFlagsTFMask |
EFlagsDFMask | EFlagsNTMask | EFlagsRFMask;
@ -189,11 +189,8 @@ BX_CPU_C::iret_protected(bxInstruction_c *i)
writeEFlags(new_eflags, changeMask);
}
else {
/* load CS-cache with new code segment descriptor */
branch_far32(&cs_selector, &cs_descriptor, (Bit32u) new_ip, cs_selector.rpl);
/* load flags with third word on stack */
write_flags(new_flags, CPL==0, CPL<=BX_CPU_THIS_PTR get_IOPL());
write_flags((Bit16u) new_eflags, CPL==0, CPL<=BX_CPU_THIS_PTR get_IOPL());
}
/* increment stack by 6/12 */
@ -267,14 +264,10 @@ BX_CPU_C::iret_protected(bxInstruction_c *i)
}
if (i->os32L()) {
new_esp = stack_read_dword(temp_ESP + 12);
new_eflags = stack_read_dword(temp_ESP + 8);
new_eip = stack_read_dword(temp_ESP + 0);
new_esp = stack_read_dword(temp_ESP + 12);
}
else {
new_esp = stack_read_word(temp_ESP + 6);
new_eflags = stack_read_word(temp_ESP + 4);
new_eip = stack_read_word(temp_ESP + 0);
new_esp = stack_read_word(temp_ESP + 6);
}
// ID,VIP,VIF,AC,VM,RF,x,NT,IOPL,OF,DF,IF,TF,SF,ZF,x,AF,x,PF,x,CF