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alexbevi
GitHub Repository: alexbevi/BizHawk
 Path: blob/master/yabause/src/dreamcast/sh2rec/sh2exec.s
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!   Copyright 2010 Lawrence Sebald

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!

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!   This file is part of Yabause.

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!

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!   Yabause is free software; you can redistribute it and/or modify

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!   it under the terms of the GNU General Public License as published by

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!   the Free Software Foundation; either version 2 of the License, or

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!   (at your option) any later version.

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!

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!   Yabause is distributed in the hope that it will be useful,

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!   but WITHOUT ANY WARRANTY; without even the implied warranty of

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!   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

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!   GNU General Public License for more details.

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!

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!   You should have received a copy of the GNU General Public License

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!   along with Yabause; if not, write to the Free Software

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!   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

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!   Code for calling upon the code generated by sh2rec (SuperH).

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    .file       "sh2exec.s"

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    .little

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    .text

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    .balign     8

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!   void sh2rec_exec(SH2_struct *cxt, u32 cycles)

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!       Execute the specified number of cycles on the given SH2 context

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    .globl  _sh2rec_exec

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_sh2rec_exec:

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    stc.l   gbr, @-r15                  ! Save call-preserved stuff

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    sts.l   mach, @-r15                 ! Ditto

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    sts.l   macl, @-r15                 ! Ditto

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    mov.l   r8, @-r15                   ! Ditto

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    mov     r4, r8                      ! Put the SH2 struct in r8

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    mov.l   r9, @-r15                   ! More call-preserved stuff

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    add     #76, r4                     ! Point at MACH in the SH2 struct

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    mov.l   r10, @-r15                  ! More call-preserved stuff

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    mov.l   r11, @-r15                  ! Last one for now...

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    lds.l   @r4+, mach                  ! Load the SH2 MACH into our MACH

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    lds.l   @r4+, macl                  ! Ditto for MACL

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    mov.l   checkInterrupts, r0         ! We need to check for interrupts...

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    mov.l   sh2memfuncsptr, r9          ! Memory access function pointer table

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    sts.l   pr, @-r15                   ! Helps to know where to go back to

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    mov     r5, r11                     ! This is important enough to keep here

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    mov.l   r5, @-r15                   ! Save this on the stack too

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    mov     r8, r4                      ! We need the original SH2_struct back

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    jsr     @r0                         ! Call sh2rec_check_interrupts

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    ldc     r8, gbr                     ! Put the SH2 struct in gbr (delay slot)

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    mov.l   findBlock, r1               ! Grab the sh2rec_find_block function

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    mov.l   @(88, gbr), r0              ! Grab the PC we are at

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.exec_loop:                             ! This is where the fun is!

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    jsr     @r1                         ! Call sh2rec_find_block

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    mov     r0, r4                      ! Move the PC to argument 1 (delay slot)

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    mov.l   @r0, r2                     ! Grab where the code is

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    mov.l   @(8, r0), r1                ! Figure out the number of cycles used

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    jsr     @r2                         ! Call the block

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    sub     r1, r11                     ! Chop off the cycles (delay slot)

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    cmp/pl  r11                         ! Are we done?

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    mov.l   findBlock, r1               ! Grab the sh2rec_find_block function

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    bt      .exec_loop                  ! Continue on if needed

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                                        ! When we are done, we will be here.

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    mov.l   r0, @(88, gbr)              ! Save the next PC value

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    mov.l   @r15+, r5                   ! Pop the requested number of cycles

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    mov     r8, r4                      ! Keep this for sanity for now

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    add     #84, r8                     ! Point just after MACL in SH2 struct

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    sts.l   macl, @-r8                  ! Store the SH2 MACL back in the struct

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    sts.l   mach, @-r8                  ! Ditto for MACH

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    lds.l   @r15+, pr                   ! Restore stuff from the stack

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    sub     r11, r5                     ! Our counter is negitive, so this works

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    mov.l   cycleOffset, r2             ! Where is the cycles member at?

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    mov.l   @r15+, r11                  ! More restoring...

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    add     r2, r4                      ! Point r4 at the cycles member

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    mov.l   @r15+, r10

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    mov.l   @r15+, r9

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    mov.l   @r15+, r8

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    lds.l   @r15+, macl

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    lds.l   @r15+, mach

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    mov.l   r5, @r4                     ! Save the cycles we spent

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    rts                                 ! Return to the caller

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    ldc.l   @r15+, gbr                  ! Last thing to restore (delay slot)

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    .balign     4

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sh2memfuncsptr:

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    .long       sh2memfuncs

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checkInterrupts:

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    .long       _sh2rec_check_interrupts

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findBlock:

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    .long       _sh2rec_find_block

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cycleOffset:

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    .long       5516

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    .data

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    .balign     4

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sh2memfuncs:

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    .long       _MappedMemoryReadByte

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    .long       _MappedMemoryReadWord

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    .long       _MappedMemoryReadLong

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    .long       _MappedMemoryWriteByte

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    .long       _MappedMemoryWriteWord

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    .long       _MappedMemoryWriteLong

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