/home/andref/projetos/epos--/src/arch/ia32/cpu.cc

// EPOS-- IA32_CPU Implementation

// This work is licensed under the Creative Commons 
// Attribution-NonCommercial-NoDerivs License. To view a copy of this license, 
// visit http://creativecommons.org/licenses/by-nc-nd/2.0/ or send a letter to 
// Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.

#include <arch/ia32/cpu.h>

__BEGIN_SYS

void IA32::Context::save() volatile
{
    // this should have been generated by GCC
    ASM("       pushl   %ebp                                            \n"
        "       movl    %esp, %ebp                                      \n"
        "       movl    8(%ebp), %esp   # this                          \n"
        "       addl    $40, %esp       # + sizeof(Context)             \n"
        "       pushl   4(%ebp)         # eip                           \n"
        "       pushfl                                                  \n"
        "       pushl   %eax                                            \n"
        "       pushl   %ecx                                            \n"
        "       pushl   %edx                                            \n"
        "       pushl   %ebx                                            \n"
        "       pushl   %ebp            # esp                           \n"
        "       pushl   (%ebp)          # ebp                           \n"
        "       pushl   %esi                                            \n"
        "       pushl   %edi                                            \n"
        "       movl    %ebp, %esp                                      \n"
        "       popl    %ebp                                            \n");
}

// POPA saves an extra "esp" (which is always "this"),
// but saves several instruction fetchs
void IA32::Context::load() const volatile
{
    ASM("       movl    4(%esp), %esp   # this  \n"
        "       popal                           \n"
        "       popfl                           \n");
}

// void IA32::Context::load() const volatile
// {
//     ASM("    movl    4(%esp), %esp   # this  \n"
//      "       popl    %edi                    \n"
//      "       popl    %esi                    \n"
//      "       popl    %ebp                    \n"
//      "       popl    %ebx                    \n"
//      "       popl    %edx                    \n"
//      "       popl    %ecx                    \n"
//      "       popl    %eax                    \n"
//      "       popfl                           \n");
// }

// The same here: one extra push and one extra pop, but several fecths less
void IA32::switch_context(Context * volatile * o, Context * volatile n)
{
    ASM("       pushfl                          \n"
        "       pushal                          \n"
        "       movl    40(%esp), %eax  # old   \n" 
        "       movl    %esp, (%eax)            \n"
        "       movl    44(%esp), %esp  # new   \n"
        "       popal                           \n"
        "       popfl                           \n");
}

// void IA32::switch_context(Context * volatile * o, Context * volatile n)
// {
//     ASM("    pushfl                          \n"
//       "      pushl   %eax                    \n"
//       "      pushl   %ecx                    \n"
//       "      pushl   %edx                    \n"
//       "      pushl   %ebx                    \n"
//       "      pushl   %ebp                    \n"
//       "      pushl   %esi                    \n"
//       "      pushl   %edi                    \n"
//       "      movl    36(%esp), %eax  # old   \n" 
//       "      movl    %esp, (%eax)            \n"
//       "      movl    40(%esp), %esp  # new   \n"
//       "      popl    %edi                    \n"
//       "      popl    %esi                    \n"
//       "      popl    %ebp                    \n"
//       "      popl    %ebx                    \n"
//       "      popl    %edx                    \n"
//       "      popl    %ecx                    \n"
//       "      popl    %eax                    \n"
//       "      popfl                           \n");
// }

__END_SYS

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