path: root/arm/arm_stub.S

.align 2

.global arm_update_gba_arm
.global arm_update_gba_thumb
.global arm_update_gba_idle_arm
.global arm_update_gba_idle_thumb

.global arm_indirect_branch_arm
.global arm_indirect_branch_thumb
.global arm_indirect_branch_dual_arm
.global arm_indirect_branch_dual_thumb

.global execute_arm_translate

.global execute_store_u8
.global execute_store_u16
.global execute_store_u32
.global execute_store_u32_safe

.global execute_load_u8
.global execute_load_s8
.global execute_load_u16
.global execute_load_s16
.global execute_load_u32

.global execute_store_cpsr
.global execute_read_spsr
.global execute_store_spsr
.global execute_spsr_restore

.global execute_swi_arm
.global execute_swi_thumb

.global execute_patch_bios_read
.global execute_patch_bios_protect

.global execute_bios_ptr_protected
.global execute_bios_rom_ptr

.global invalidate_icache_region
.global invalidate_cache_region

.global memory_map_read
.global memory_map_write
.global reg

#define REG_BASE_OFFSET   1024

#define REG_R0            (REG_BASE_OFFSET + (0 * 4))
#define REG_R1            (REG_BASE_OFFSET + (1 * 4))
#define REG_R2            (REG_BASE_OFFSET + (2 * 4))
#define REG_R3            (REG_BASE_OFFSET + (3 * 4))
#define REG_R4            (REG_BASE_OFFSET + (4 * 4))
#define REG_R5            (REG_BASE_OFFSET + (5 * 4))
#define REG_R6            (REG_BASE_OFFSET + (6 * 4))
#define REG_R7            (REG_BASE_OFFSET + (7 * 4))
#define REG_R8            (REG_BASE_OFFSET + (8 * 4))
#define REG_R9            (REG_BASE_OFFSET + (9 * 4))
#define REG_R10           (REG_BASE_OFFSET + (10 * 4))
#define REG_R11           (REG_BASE_OFFSET + (11 * 4))
#define REG_R12           (REG_BASE_OFFSET + (12 * 4))
#define REG_R13           (REG_BASE_OFFSET + (13 * 4))
#define REG_R14           (REG_BASE_OFFSET + (14 * 4))
#define REG_SP            (REG_BASE_OFFSET + (13 * 4))
#define REG_LR            (REG_BASE_OFFSET + (14 * 4))
#define REG_PC            (REG_BASE_OFFSET + (15 * 4))

#define REG_N_FLAG        (REG_BASE_OFFSET + (16 * 4))
#define REG_Z_FLAG        (REG_BASE_OFFSET + (17 * 4))
#define REG_C_FLAG        (REG_BASE_OFFSET + (18 * 4))
#define REG_V_FLAG        (REG_BASE_OFFSET + (19 * 4))
#define REG_CPSR          (REG_BASE_OFFSET + (20 * 4))

#define REG_SAVE          (REG_BASE_OFFSET + (21 * 4))
#define REG_SAVE2         (REG_BASE_OFFSET + (22 * 4))
#define REG_SAVE3         (REG_BASE_OFFSET + (23 * 4))

#define CPU_MODE          (REG_BASE_OFFSET + (29 * 4))
#define CPU_HALT_STATE    (REG_BASE_OFFSET + (30 * 4))
#define CHANGED_PC_STATUS (REG_BASE_OFFSET + (31 * 4))


#define reg_a0            r0
#define reg_a1            r1
#define reg_a2            r2

#define reg_s0            r9
#define reg_base          sp
#define reg_flags         r11

#define reg_cycles        r12

#define reg_x0            r3
#define reg_x1            r4
#define reg_x2            r5
#define reg_x3            r6
#define reg_x4            r7
#define reg_x5            r8


#define MODE_SUPERVISOR   3


#ifdef __ARM_ARCH_7A__
  #define extract_u16(rd, rs) \
    uxth rd, rs
#else
  #define extract_u16(rd, rs) \
    bic  rd, rs, #0xff000000 ;\
    bic  rd, rd, #0x00ff0000
#endif

@ Will load the register set from memory into the appropriate cached registers.
@ See arm_emit.h for listing explanation.

#define load_registers_arm()                                                 ;\
  ldr reg_x0, [reg_base, #REG_R0]                                            ;\
  ldr reg_x1, [reg_base, #REG_R1]                                            ;\
  ldr reg_x2, [reg_base, #REG_R6]                                            ;\
  ldr reg_x3, [reg_base, #REG_R9]                                            ;\
  ldr reg_x4, [reg_base, #REG_R12]                                           ;\
  ldr reg_x5, [reg_base, #REG_R14]                                           ;\

#define load_registers_thumb()                                               ;\
  ldr reg_x0, [reg_base, #REG_R0]                                            ;\
  ldr reg_x1, [reg_base, #REG_R1]                                            ;\
  ldr reg_x2, [reg_base, #REG_R2]                                            ;\
  ldr reg_x3, [reg_base, #REG_R3]                                            ;\
  ldr reg_x4, [reg_base, #REG_R4]                                            ;\
  ldr reg_x5, [reg_base, #REG_R5]                                            ;\


@ Will store the register set from cached registers back to memory.

#define store_registers_arm()                                                ;\
  str reg_x0, [reg_base, #REG_R0]                                            ;\
  str reg_x1, [reg_base, #REG_R1]                                            ;\
  str reg_x2, [reg_base, #REG_R6]                                            ;\
  str reg_x3, [reg_base, #REG_R9]                                            ;\
  str reg_x4, [reg_base, #REG_R12]                                           ;\
  str reg_x5, [reg_base, #REG_R14]                                           ;\

#define store_registers_thumb()                                              ;\
  str reg_x0, [reg_base, #REG_R0]                                            ;\
  str reg_x1, [reg_base, #REG_R1]                                            ;\
  str reg_x2, [reg_base, #REG_R2]                                            ;\
  str reg_x3, [reg_base, #REG_R3]                                            ;\
  str reg_x4, [reg_base, #REG_R4]                                            ;\
  str reg_x5, [reg_base, #REG_R5]                                            ;\


@ Returns an updated persistent cpsr with the cached flags register.
@ Uses reg as a temporary register and returns the CPSR here.

#define collapse_flags_no_update(reg)                                        ;\
  ldr reg, [reg_base, #REG_CPSR]          /* reg = cpsr                    */;\
  bic reg, reg, #0xF0000000               /* clear ALU flags in cpsr       */;\
  and reg_flags, reg_flags, #0xF0000000   /* clear non-ALU flags           */;\
  orr reg, reg, reg_flags                 /* update cpsr with ALU flags    */;\

@ Updates cpsr using the above macro.

#define collapse_flags(reg)                                                  ;\
  collapse_flags_no_update(reg)                                              ;\
  str reg, [reg_base, #REG_CPSR]                                             ;\

@ Loads the saved flags register from the persistent cpsr.

#define extract_flags()                                                      ;\
  ldr reg_flags, [reg_base, #REG_CPSR]                                       ;\
  msr cpsr_f, reg_flags                                                      ;\


#define save_flags()                                                         ;\
  mrs reg_flags, cpsr                                                        ;\

#define restore_flags()                                                      ;\
  msr cpsr_f, reg_flags                                                      ;\

#ifdef __ARM_EABI__
  @ must align stack
  #define call_c_saved_regs r2, r3, r12, lr
#else
  #define call_c_saved_regs r3, r12, lr
#endif

@ Calls a C function - all caller save registers which are important to the
@ dynarec and to returning from this function are saved.

#define call_c_function(function)                                            ;\
  stmdb sp!, { call_c_saved_regs }                                           ;\
  bl function                                                                ;\
  ldmia sp!, { call_c_saved_regs }                                           ;\


@ Update the GBA hardware (video, sound, input, etc)

@ Input:
@ r0: current PC

#define return_straight()                                                    ;\
  bx lr                                                                      ;\

#define return_add()                                                         ;\
  add pc, lr, #4                                                             ;\

#define load_pc_straight()                                                   ;\
  ldr r0, [lr, #-8]                                                          ;\

#define load_pc_add()                                                        ;\
  ldr r0, [lr]                                                               ;\


#define arm_update_gba_builder(name, mode, return_op)                        ;\
                                                                             ;\
arm_update_gba_##name:                                                       ;\
  load_pc_##return_op()                                                      ;\
  str r0, [reg_base, #REG_PC]             /* write out the PC              */;\
                                                                             ;\
  save_flags()                                                               ;\
  collapse_flags(r0)                      /* update the flags              */;\
                                                                             ;\
  store_registers_##mode()                /* save out registers            */;\
  call_c_function(update_gba)             /* update GBA state              */;\
                                                                             ;\
  mvn reg_cycles, r0                      /* load new cycle count          */;\
                                                                             ;\
  ldr r0, [reg_base, #CHANGED_PC_STATUS]  /* load PC changed status        */;\
  cmp r0, #0                              /* see if PC has changed         */;\
  beq 1f                                  /* if not return                 */;\
                                                                             ;\
  ldr r0, [reg_base, #REG_PC]             /* load new PC                   */;\
  ldr r1, [reg_base, #REG_CPSR]           /* r1 = flags                    */;\
  tst r1, #0x20                           /* see if Thumb bit is set       */;\
  bne 2f                                  /* if so load Thumb PC           */;\
                                                                             ;\
  load_registers_arm()                    /* load ARM regs                 */;\
  call_c_function(block_lookup_address_arm)                                  ;\
  restore_flags()                                                            ;\
  bx r0                                   /* jump to new ARM block         */;\
                                                                             ;\
1:                                                                           ;\
  load_registers_##mode()                 /* reload registers              */;\
  restore_flags()                                                            ;\
  return_##return_op()                                                       ;\
                                                                             ;\
2:                                                                           ;\
  load_registers_thumb()                  /* load Thumb regs               */;\
  call_c_function(block_lookup_address_thumb)                                ;\
  restore_flags()                                                            ;\
  bx r0                                   /* jump to new ARM block         */;\


arm_update_gba_builder(arm, arm, straight)
arm_update_gba_builder(thumb, thumb, straight)

arm_update_gba_builder(idle_arm, arm, add)
arm_update_gba_builder(idle_thumb, thumb, add)



@ These are b stubs for performing indirect branches. They are not
@ linked to and don't return, instead they link elsewhere.

@ Input:
@ r0: PC to branch to

arm_indirect_branch_arm:
  save_flags()
  call_c_function(block_lookup_address_arm)
  restore_flags()
  bx r0

arm_indirect_branch_thumb:
  save_flags()
  call_c_function(block_lookup_address_thumb)
  restore_flags()
  bx r0

arm_indirect_branch_dual_arm:
  save_flags()
  tst r0, #0x01                           @ check lower bit
  bne 1f                                  @ if set going to Thumb mode
  call_c_function(block_lookup_address_arm)
  restore_flags()
  bx r0                                   @ return

1:
  bic r0, r0, #0x01
  store_registers_arm()                   @ save out ARM registers
  load_registers_thumb()                  @ load in Thumb registers
  ldr r1, [reg_base, #REG_CPSR]           @ load cpsr
  orr r1, r1, #0x20                       @ set Thumb mode
  str r1, [reg_base, #REG_CPSR]           @ store flags
  call_c_function(block_lookup_address_thumb)
  restore_flags()
  bx r0                                   @ return

arm_indirect_branch_dual_thumb:
  save_flags()
  tst r0, #0x01                           @ check lower bit
  beq 1f                                  @ if set going to ARM mode
  bic r0, r0, #0x01
  call_c_function(block_lookup_address_thumb)
  restore_flags()
  bx r0                                   @ return

1:
  store_registers_thumb()                 @ save out Thumb registers
  load_registers_arm()                    @ load in ARM registers
  ldr r1, [reg_base, #REG_CPSR]           @ load cpsr
  bic r1, r1, #0x20                       @ clear Thumb mode
  str r1, [reg_base, #REG_CPSR]           @ store flags
  call_c_function(block_lookup_address_arm)
  restore_flags()
  bx r0                                   @ return


@ Update the cpsr.

@ Input:
@ r0: new cpsr value
@ r1: bitmask of which bits in cpsr to update
@ r2: current PC

execute_store_cpsr:
  save_flags()
  and reg_flags, r0, r1                   @ reg_flags = new_cpsr & store_mask
  ldr r0, [reg_base, #REG_CPSR]           @ r0 = cpsr
  bic r0, r0, r1                          @ r0 = cpsr & ~store_mask
  orr reg_flags, reg_flags, r0            @ reg_flags = new_cpsr | cpsr

  mov r0, reg_flags                       @ also put new cpsr in r0

  store_registers_arm()                   @ save ARM registers
  ldr r2, [lr]                            @ r2 = pc
  call_c_function(execute_store_cpsr_body)
  load_registers_arm()                    @ restore ARM registers

  cmp r0, #0                              @ check new PC
  beq 1f                                  @ if it's zero, return

  call_c_function(block_lookup_address_arm)

  restore_flags()
  bx r0                                   @ return to new ARM address

1:
  restore_flags()
  add pc, lr, #4                          @ return


@ Update the current spsr.

@ Input:
@ r0: new cpsr value
@ r1: bitmask of which bits in spsr to update

execute_store_spsr:
  ldr r1, =spsr                           @ r1 = spsr
  ldr r2, [reg_base, #CPU_MODE]           @ r2 = CPU_MODE
  str r0, [r1, r2, lsl #2]                @ spsr[CPU_MODE] = new_spsr
  bx lr

@ Read the current spsr.

@ Output:
@ r0: spsr

execute_read_spsr:
  ldr r0, =spsr                           @ r0 = spsr
  ldr r1, [reg_base, #CPU_MODE]           @ r1 = CPU_MODE
  ldr r0, [r0, r1, lsl #2]                @ r0 = spsr[CPU_MODE]
  bx lr                                   @ return


@ Restore the cpsr from the mode spsr and mode shift.

@ Input:
@ r0: current pc

execute_spsr_restore:
  save_flags()
  ldr r1, =spsr                           @ r1 = spsr
  ldr r2, [reg_base, #CPU_MODE]           @ r2 = cpu_mode
  ldr r1, [r1, r2, lsl #2]                @ r1 = spsr[cpu_mode] (new cpsr)
  str r1, [reg_base, #REG_CPSR]           @ update cpsr
  mov reg_flags, r1                       @ also, update shadow flags

  @ This function call will pass r0 (address) and return it.
  store_registers_arm()                   @ save ARM registers
  call_c_function(execute_spsr_restore_body)

  ldr r1, [reg_base, #REG_CPSR]           @ r1 = cpsr
  tst r1, #0x20                           @ see if Thumb mode is set
  bne 2f                                  @ if so handle it

  load_registers_arm()                    @ restore ARM registers
  call_c_function(block_lookup_address_arm)
  restore_flags()
  bx r0

2:
  load_registers_thumb()                  @ load Thumb registers
  call_c_function(block_lookup_address_thumb)
  restore_flags()
  bx r0



@ Setup the mode transition work for calling an SWI.

@ Input:
@ r0: current pc

#define execute_swi_builder(mode)                                            ;\
                                                                             ;\
execute_swi_##mode:                                                          ;\
  save_flags()                                                               ;\
  ldr r1, =reg_mode                       /* r1 = reg_mode                 */;\
  /* reg_mode[MODE_SUPERVISOR][6] = pc                                     */;\
  ldr r0, [lr]                            /* load PC                       */;\
  str r0, [r1, #((MODE_SUPERVISOR * (7 * 4)) + (6 * 4))]                     ;\
  collapse_flags_no_update(r0)            /* r0 = cpsr                     */;\
  ldr r1, =spsr                           /* r1 = spsr                     */;\
  str r0, [r1, #(MODE_SUPERVISOR * 4)]    /* spsr[MODE_SUPERVISOR] = cpsr  */;\
  bic r0, r0, #0x3F                       /* clear mode flag in r0         */;\
  orr r0, r0, #0x13                       /* set to supervisor mode        */;\
  str r0, [reg_base, #REG_CPSR]           /* update cpsr                   */;\
                                                                             ;\
  call_c_function(bios_region_read_allow)                                    ;\
                                                                             ;\
  mov r0, #MODE_SUPERVISOR                                                   ;\
                                                                             ;\
  store_registers_##mode()                /* store regs for mode           */;\
  call_c_function(set_cpu_mode)           /* set the CPU mode to svsr      */;\
  load_registers_arm()                    /* load ARM regs                 */;\
                                                                             ;\
  restore_flags()                                                            ;\
  add pc, lr, #4                          /* return                        */;\

execute_swi_builder(arm)
execute_swi_builder(thumb)


@ Wrapper for calling SWI functions in C (or can implement some in ASM if
@ desired)

#define execute_swi_function_builder(swi_function, mode)                     ;\
                                                                             ;\
  .global execute_swi_hle_##swi_function##_##mode                            ;\
execute_swi_hle_##swi_function##_##mode:                                     ;\
  save_flags()                                                               ;\
  store_registers_##mode()                                                   ;\
  call_c_function(execute_swi_hle_##swi_function##_c)                        ;\
  load_registers_##mode()                                                    ;\
  restore_flags()                                                            ;\
  bx lr                                                                      ;\

execute_swi_function_builder(div, arm)
execute_swi_function_builder(div, thumb)


@ Start program execution. Normally the mode should be Thumb and the
@ PC should be 0x8000000, however if a save state is preloaded this
@ will be different.

@ Input:
@ r0: initial value for cycle counter

@ Uses sp as reg_base; must hold consistently true.

execute_arm_translate:
  sub sp, sp, #0x100                      @ allocate room for register data

  mvn reg_cycles, r0                      @ load cycle counter

  mov r0, reg_base                        @ load reg_base into first param
  call_c_function(move_reg)               @ make reg_base the new reg ptr

  sub sp, sp, #REG_BASE_OFFSET            @ allocate room for ptr table
  bl load_ptr_read_function_table         @ load read function ptr table

  ldr r0, [reg_base, #REG_PC]             @ r0 = current pc
  ldr r1, [reg_base, #REG_CPSR]           @ r1 = flags
  tst r1, #0x20                           @ see if Thumb bit is set

  bne 1f                                  @ if so lookup thumb

  load_registers_arm()                    @ load ARM registers
  call_c_function(block_lookup_address_arm)
  extract_flags()                         @ load flags
  bx r0                                   @ jump to first ARM block

1:
  load_registers_thumb()                  @ load Thumb registers
  call_c_function(block_lookup_address_thumb)
  extract_flags()                         @ load flags
  bx r0                                   @ jump to first Thumb block


@ Write out to memory.

@ Input:
@ r0: address
@ r1: value
@ r2: current pc

#define execute_store_body(store_type, store_op)                             ;\
  save_flags()                                                               ;\
  stmdb sp!, { lr }                       /* save lr                       */;\
  tst r0, #0xF0000000                     /* make sure address is in range */;\
  bne ext_store_u##store_type             /* if not do ext store           */;\
                                                                             ;\
  ldr r2, =memory_map_write               /* r2 = memory_map_write         */;\
  mov lr, r0, lsr #15                     /* lr = page index of address    */;\
  ldr r2, [r2, lr, lsl #2]                /* r2 = memory page              */;\
                                                                             ;\
  cmp r2, #0                              /* see if map is ext             */;\
  beq ext_store_u##store_type             /* if so do ext store            */;\
                                                                             ;\
  mov r0, r0, lsl #17                     /* isolate bottom 15 bits in top */;\
  mov r0, r0, lsr #17                     /* like performing and 0x7FFF    */;\
  store_op r1, [r2, r0]                   /* store result                  */;\


#define store_align_8()                                                      ;\
  and r1, r1, #0xff                                                          ;\

#define store_align_16()                                                     ;\
  bic r0, r0, #0x01                                                          ;\
  extract_u16(r1, r1)                                                        ;\

#define store_align_32()                                                     ;\
  bic r0, r0, #0x03                                                          ;\


#define execute_store_builder(store_type, store_op, load_op)                 ;\
                                                                             ;\
execute_store_u##store_type:                                                 ;\
  execute_store_body(store_type, store_op)                                   ;\
  sub r2, r2, #0x8000                     /* Pointer to code status data   */;\
  load_op r0, [r2, r0]                    /* check code flag               */;\
                                                                             ;\
  cmp r0, #0                              /* see if it's not 0             */;\
  bne 2f                                  /* if so perform smc write       */;\
  ldmia sp!, { lr }                       /* restore lr                    */;\
  restore_flags()                                                            ;\
  add pc, lr, #4                          /* return                        */;\
                                                                             ;\
2:                                                                           ;\
  ldmia sp!, { lr }                       /* restore lr                    */;\
  ldr r0, [lr]                            /* load PC                       */;\
  str r0, [reg_base, #REG_PC]             /* write out PC                  */;\
  b smc_write                             /* perform smc write             */;\
                                                                             ;\
ext_store_u##store_type:                                                     ;\
  ldmia sp!, { lr }                       /* pop lr off of stack           */;\
  ldr r2, [lr]                            /* load PC                       */;\
  str r2, [reg_base, #REG_PC]             /* write out PC                  */;\
  store_align_##store_type()                                                 ;\
  call_c_function(write_memory##store_type)                                  ;\
  b write_epilogue                        /* handle additional write stuff */;\

execute_store_builder(8, strb, ldrb)
execute_store_builder(16, strh, ldrh)
execute_store_builder(32, str, ldr)


execute_store_u32_safe:
  execute_store_body(32_safe, str)
  restore_flags()
  ldmia sp!, { pc }                       @ return

ext_store_u32_safe:
  ldmia sp!, { lr }                       @ Restore lr
  call_c_function(write_memory32)         @ Perform 32bit store
  restore_flags()
  bx lr                                   @ Return


write_epilogue:
  cmp r0, #0                              @ check if the write rose an alert
  beq 4f                                  @ if not we can exit

  collapse_flags(r1)                      @ interrupt needs current flags

  cmp r0, #2                              @ see if the alert is due to SMC
  beq smc_write                           @ if so, goto SMC handler

  ldr r1, [reg_base, #REG_CPSR]           @ r1 = cpsr
  tst r1, #0x20                           @ see if Thumb bit is set
  bne 1f                                  @ if so do Thumb update

  store_registers_arm()                   @ save ARM registers

3:
  bl update_gba                           @ update GBA until CPU isn't halted

  mvn reg_cycles, r0                      @ load new cycle count
  ldr r0, [reg_base, #REG_PC]             @ load new PC
  ldr r1, [reg_base, #REG_CPSR]           @ r1 = flags
  tst r1, #0x20                           @ see if Thumb bit is set
  bne 2f

  load_registers_arm()
  call_c_function(block_lookup_address_arm)
  restore_flags()
  bx r0                                   @ jump to new ARM block

1:
  store_registers_thumb()                 @ save Thumb registers
  b 3b

2:
  load_registers_thumb()
  call_c_function(block_lookup_address_thumb)
  restore_flags()
  bx r0                                   @ jump to new Thumb block

4:
  restore_flags()
  add pc, lr, #4                          @ return


smc_write:
  call_c_function(flush_translation_cache_ram)

lookup_pc:
  ldr r0, [reg_base, #REG_PC]             @ r0 = new pc
  ldr r1, [reg_base, #REG_CPSR]           @ r1 = flags
  tst r1, #0x20                           @ see if Thumb bit is set
  beq lookup_pc_arm                       @ if not lookup ARM

lookup_pc_thumb:
  call_c_function(block_lookup_address_thumb)
  restore_flags()
  bx r0                                   @ jump to new Thumb block

lookup_pc_arm:
  call_c_function(block_lookup_address_arm)
  restore_flags()
  bx r0                                   @ jump to new ARM block


#define sign_extend_u8(reg)
#define sign_extend_u16(reg)
#define sign_extend_u32(reg)

#define sign_extend_s8(reg)                                                  ;\
  mov reg, reg, lsl #24                   /* shift reg into upper 8bits    */;\
  mov reg, reg, asr #24                   /* shift down, sign extending    */;\

#define sign_extend_s16(reg)                                                 ;\
  mov reg, reg, lsl #16                   /* shift reg into upper 16bits   */;\
  mov reg, reg, asr #16                   /* shift down, sign extending    */;\

#define execute_load_op_u8(load_op)                                          ;\
  mov r0, r0, lsl #17                                                        ;\
  load_op r0, [r2, r0, lsr #17]                                              ;\

#define execute_load_op_s8(load_op)                                          ;\
  mov r0, r0, lsl #17                                                        ;\
  mov r0, r0, lsr #17                                                        ;\
  load_op r0, [r2, r0]                                                       ;\

#define execute_load_op_u16(load_op)                                         ;\
  execute_load_op_s8(load_op)                                                ;\

#define execute_load_op_s16(load_op)                                         ;\
  execute_load_op_s8(load_op)                                                ;\

#define execute_load_op_u16(load_op)                                         ;\
  execute_load_op_s8(load_op)                                                ;\

#define execute_load_op_u32(load_op)                                         ;\
  execute_load_op_u8(load_op)                                                ;\


#define execute_load_builder(load_type, load_function, load_op, mask)        ;\
                                                                             ;\
execute_load_##load_type:                                                    ;\
  save_flags()                                                               ;\
  tst r0, mask                            /* make sure address is in range */;\
  bne ext_load_##load_type                /* if not do ext load            */;\
                                                                             ;\
  ldr r2, =memory_map_read                /* r2 = memory_map_read          */;\
  mov r1, r0, lsr #15                     /* r1 = page index of address    */;\
  ldr r2, [r2, r1, lsl #2]                /* r2 = memory page              */;\
                                                                             ;\
  cmp r2, #0                              /* see if map is ext             */;\
  beq ext_load_##load_type                /* if so do ext load             */;\
                                                                             ;\
  execute_load_op_##load_type(load_op)                                       ;\
  restore_flags()                                                            ;\
  add pc, lr, #4                          /* return                        */;\
                                                                             ;\
ext_load_##load_type:                                                        ;\
  ldr r1, [lr]                            /* r1 = PC                       */;\
  str r1, [reg_base, #REG_PC]             /* update PC                     */;\
  call_c_function(read_memory##load_function)                                ;\
  sign_extend_##load_type(r0)             /* sign extend result            */;\
  restore_flags()                                                            ;\
  add pc, lr, #4                          /* return                        */;\


execute_load_builder(u8, 8, ldrneb, #0xF0000000)
execute_load_builder(s8, 8, ldrnesb, #0xF0000000)
execute_load_builder(u16, 16, ldrneh, #0xF0000001)
execute_load_builder(s16, 16_signed, ldrnesh, #0xF0000001)
execute_load_builder(u32, 32, ldrne, #0xF0000000)


#define execute_ptr_builder(region, ptr, bits)                               ;\
                                                                             ;\
execute_##region##_ptr:                                                      ;\
  ldr r1, =(ptr)                          /* load region ptr               */;\
  mov r0, r0, lsl #(32 - bits)            /* isolate bottom bits           */;\
  mov r0, r0, lsr #(32 - bits)                                               ;\
  bx lr                                   /* return                        */;\


execute_bios_ptr_protected:
  ldr r1, =bios_read_protect              @ load bios read ptr
  and r0, r0, #0x03                       @ only want bottom 2 bits
  bx lr                                   @ return


@ address = (address & 0x7FFF) + ((address & 0x38000) * 2) + 0x8000;

execute_ewram_ptr:
  ldr r1, =(ewram + 0x8000)               @ load ewram read ptr
  mov r2, r0, lsl #17                     @ isolate bottom 15 bits
  mov r2, r2, lsr #17
  and r0, r0, #0x38000                    @ isolate top 2 bits
  add r0, r2, r0, lsl #1                  @ add top 2 bits * 2 to bottom 15
  bx lr                                   @ return


@  u32 gamepak_index = address >> 15;
@  u8 *map = memory_map_read[gamepak_index];

@  if(!map)
@    map = load_gamepak_page(gamepak_index & 0x3FF);

@  value = address##type(map, address & 0x7FFF)

execute_gamepak_ptr:
  ldr r1, =memory_map_read                @ load memory_map_read
  mov r2, r0, lsr #15                     @ isolate top 17 bits
  ldr r1, [r1, r2, lsl #2]                @ load memory map read ptr

  save_flags()
  cmp r1, #0                              @ see if map entry is NULL
  bne 2f                                  @ if not resume

  stmdb sp!, { r0 }                       @ save r0 on stack
  mov r2, r2, lsl #20                     @ isolate page index
  mov r0, r2, lsr #20
  call_c_function(load_gamepak_page)      @ read new page into r0

  mov r1, r0                              @ new map = return
  ldmia sp!, { r0 }                       @ restore r0

2:
  mov r0, r0, lsl #17                     @ isolate bottom 15 bits
  mov r0, r0, lsr #17
  restore_flags()
  bx lr                                   @ return


@ These will store the result in a pointer, then pass that pointer.

execute_eeprom_ptr:
  save_flags()

  call_c_function(read_eeprom)            @ load EEPROM result
  add r1, reg_base, #(REG_SAVE & 0xFF00)
  add r1, r1, #(REG_SAVE & 0xFF)
  strh r0, [r1]                           @ write result out
  mov r0, #0                              @ zero out address

  restore_flags()
  bx lr                                   @ return


execute_backup_ptr:
  save_flags()

  mov r0, r0, lsl #16                     @ only want top 16 bits
  mov r0, r0, lsr #16
  call_c_function(read_backup)            @ load backup result
  add r1, reg_base, #(REG_SAVE & 0xFF00)
  add r1, r1, #(REG_SAVE & 0xFF)
  strb r0, [r1]                           @ write result out
  mov r0, #0                              @ zero out address

  restore_flags()
  bx lr                                   @ return


execute_open_ptr:
  ldr r1, [reg_base, #REG_CPSR]           @ r1 = cpsr
  save_flags()

  stmdb sp!, { r0 }                       @ save r0

  ldr r0, [lr, #-4]                       @ r0 = current PC

  tst r1, #0x20                           @ see if Thumb bit is set
  bne 1f                                  @ if so load Thumb op

  call_c_function(read_memory32)          @ read open address

  add r1, reg_base, #((REG_SAVE + 4) & 0xFF00)
  add r1, r1, #((REG_SAVE + 4) & 0xFF)
  add r1, r1, reg_base
  str r0, [r1]                            @ write out

  ldmia sp!, { r0 }                       @ restore r0
  and r0, r0, #0x03                       @ isolate bottom 2 bits

  restore_flags()
  bx lr

1:
  call_c_function(read_memory16)          @ read open address

  orr r0, r0, r0, lsl #16                 @ duplicate opcode over halves
  add r1, reg_base, #((REG_SAVE + 4) & 0xFF00)
  add r1, r1, #((REG_SAVE + 4) & 0xFF)

  add r1, r1, reg_base
  str r0, [r1]                            @ write out

  ldmia sp!, { r0 }                       @ restore r0
  and r0, r0, #0x03                       @ isolate bottom 2 bits

  restore_flags();
  bx lr


execute_ptr_builder(bios_rom, bios_rom, 14)
execute_ptr_builder(iwram, iwram + 0x8000, 15)
execute_ptr_builder(vram, vram, 17)
execute_ptr_builder(oam_ram, oam_ram, 10)
execute_ptr_builder(io_registers, io_registers, 10)
execute_ptr_builder(palette_ram, palette_ram, 10)

ptr_read_function_table:
  .word execute_bios_ptr_protected        @ 0x00: BIOS
  .word execute_open_ptr                  @ 0x01: open
  .word execute_ewram_ptr                 @ 0x02: ewram
  .word execute_iwram_ptr                 @ 0x03: iwram
  .word execute_io_registers_ptr          @ 0x04: I/O registers
  .word execute_palette_ram_ptr           @ 0x05: palette RAM
  .word execute_vram_ptr                  @ 0x06: vram
  .word execute_oam_ram_ptr               @ 0x07: oam RAM
  .word execute_gamepak_ptr               @ 0x08: gamepak
  .word execute_gamepak_ptr               @ 0x09: gamepak
  .word execute_gamepak_ptr               @ 0x0A: gamepak
  .word execute_gamepak_ptr               @ 0x0B: gamepak
  .word execute_gamepak_ptr               @ 0x0C: gamepak
  .word execute_eeprom_ptr                @ 0x0D: EEPROM
  .word execute_backup_ptr                @ 0x0E: backup

.rept (256 - 15)                          @ 0x0F - 0xFF: open
  .word execute_open_ptr
.endr


@ Setup the read function table.
@ Load this onto the the stack; assume we're free to use r3

load_ptr_read_function_table:
  mov r0, #256                            @ 256 elements
  ldr r1, =ptr_read_function_table        @ r0 = ptr_read_function_table
  mov r2, sp                              @ load here

2:
  ldr r3, [r1], #4                        @ read pointer
  str r3, [r2], #4                        @ write pointer

  subs r0, r0, #1                         @ goto next iteration
  bne 2b

  bx lr


@ Patch the read function table to allow for BIOS reads.

execute_patch_bios_read:
  ldr r1, =reg                            @ r1 = reg
  ldr r0, =execute_bios_rom_ptr           @ r0 = patch function
  ldr r1, [r1]
  str r0, [r1, #-REG_BASE_OFFSET]
  bx lr


@ Patch the read function table to allow for BIOS reads.

execute_patch_bios_protect:
  ldr r1, =reg                            @ r1 = reg
  ldr r0, =execute_bios_ptr_protected     @ r0 = patch function
  ldr r1, [r1]
  str r0, [r1, #-REG_BASE_OFFSET]
  bx lr


#define save_reg_scratch(reg)                                                 ;\
  ldr r2, [reg_base, #(REG_BASE_OFFSET + (reg * 4))]                          ;\
  str r2, [reg_base, #(REG_BASE_OFFSET + (reg * 4) + 128)]                    ;\

#define restore_reg_scratch(reg)                                              ;\
  ldr r2, [reg_base, #(REG_BASE_OFFSET + (reg * 4) + 128)]                    ;\
  str r2, [reg_base, #(REG_BASE_OFFSET + (reg * 4))]                          ;\

#define scratch_regs_thumb(type)                                              ;\
  type##_reg_scratch(0)                                                       ;\
  type##_reg_scratch(1)                                                       ;\
  type##_reg_scratch(2)                                                       ;\
  type##_reg_scratch(3)                                                       ;\
  type##_reg_scratch(4)                                                       ;\
  type##_reg_scratch(5)                                                       ;\

#define scratch_regs_arm(type)                                                ;\
  type##_reg_scratch(0)                                                       ;\
  type##_reg_scratch(1)                                                       ;\
  type##_reg_scratch(6)                                                       ;\
  type##_reg_scratch(9)                                                       ;\
  type##_reg_scratch(12)                                                      ;\
  type##_reg_scratch(14)                                                      ;\

.pool

.comm memory_map_read 0x8000
.comm memory_map_write 0x8000