source: trunk/libs/newlib/src/libgloss/arc/crt0.S @ 536

/*
   Copyright (c) 2015-2016, Synopsys, Inc. All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

   1) Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.

   2) Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

   3) Neither the name of the Synopsys, Inc., nor the names of its contributors
   may be used to endorse or promote products derived from this software
   without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
   LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   POSSIBILITY OF SUCH DAMAGE.
*/

/*
   The startup code for the ARC family of processors does the following before
   transferring control to user defined main label:
       1.  Set sp to __stack_top (link time variable)
       2.  Set fp to zero
       3.  Zero out the bss section (for uninitialized globals)
   After returning from main, the processor is halted and the pipeline is
   flushed out.

   We expect argc in r0 and argv in r1.  These are saved in r13 / r14 during
   the initialization code.
*/

/* Compatibility with older ARC GCC, that doesn't provide some of the
   preprocessor defines used by newlib and libgloss for ARC.  */
#if defined (__Xbarrel_shifter) && !defined (__ARC_BARREL_SHIFTER__)
#define __ARC_BARREL_SHIFTER__ 1
#endif

#if defined (__EM__) && !defined (__ARCEM__)
#define __ARCEM__ 1
#endif

#if defined (__HS__) && !defined (__ARCHS__)
#define __ARCHS__ 1
#endif

        .file   "crt0.S"
        .extern main

#if defined (__ARCEM__) || defined (__ARCHS__)
        .section .ivt, "a", @progbits

; Helper macro to define weak symbols to include into interrupt vector table.
; User code may define those functions in them, so user function will be
; referenced in the IVT. By default all handlers point to _exit_halt - so they
; always cause application halt, because if application causes an exception or
; interrupt, but doesn't set a handler for it - something is wrong in
; application. Exception is "start" entry of IVT, which points to __start
; function.
#define IVT_ENTRY(name) \
    .word name `\
    .weak name `\
    .set name, _exit_halt

; handler's name,          number, name,       offset in IVT (hex/dec)
.word __start                ; 0   program entry point  0x0     0
IVT_ENTRY(memory_error)      ; 1   memory_error         0x4     4
IVT_ENTRY(instruction_error) ; 2   instruction_error    0x8     8
IVT_ENTRY(EV_MachineCheck)   ; 3   EV_MachineCheck      0xC     12
IVT_ENTRY(EV_TLBMissI)       ; 4   EV_TLBMissI          0x10    16
IVT_ENTRY(EV_TLBMissD)       ; 5   EV_TLBMissD          0x14    20
IVT_ENTRY(EV_ProtV)          ; 6   EV_ProtV             0x18    24
IVT_ENTRY(EV_PrivilegeV)     ; 7   EV_PrivilegeV        0x1C    28
IVT_ENTRY(EV_SWI)            ; 8   EV_SWI               0x20    32
IVT_ENTRY(EV_Trap)           ; 9   EV_Trap              0x24    36
IVT_ENTRY(EV_Extension)      ; 10  EV_Extension         0x28    40
IVT_ENTRY(EV_DivZero)        ; 11  EV_DivZero           0x2C    44
IVT_ENTRY(EV_DCError)        ; 12  EV_DCError           0x30    48
IVT_ENTRY(EV_Maligned)       ; 13  EV_Maligned          0x34    52
IVT_ENTRY(EV_Ex14)           ; 14  unused               0x38    56
IVT_ENTRY(EV_Ex15)           ; 15  unused               0x3C    60
IVT_ENTRY(IRQ_Timer0)        ; 16  Timer 0              0x40    64
IVT_ENTRY(IRQ_Timer1)        ; 17  Timer 1              0x44    68
IVT_ENTRY(IRQ_18)            ; 18                       0x48    72
IVT_ENTRY(IRQ_19)            ; 19                       0x4C    76
IVT_ENTRY(IRQ_20)            ; 20                       0x50    80

        .section .text.__startup, "ax", @progbits
#else
        .text
#endif /* __ARCEM__ || __ARCHS__ */

        .global __start
        .type   __start, @function
        .align 4
#ifdef __ARC601__
; Startup code for the ARC601 processor
__start:
        mov     gp, @__SDATA_BEGIN__
        mov     sp, @__stack_top        ; Point to top of stack
        mov     r5, 0                   ; Zero value
        mov_s   r2, @__sbss_start       ; r2 = start of the bss section
        sub     r3, @_end, r2           ; r3 = size of the bss section in bytes

        asr_s   r3, r3
        asr_s   r3, r3                  ; r3 = size of bss in words

.Lbss_loop:
        cmp     r3, 0xff                ; Check for max lp_count
        mov.le  lp_count, r3
        mov.gt  lp_count, 0xff
        lpnz    2f                      ; Loop to zero bss
        st.ab   r5,[r2, 4]              ; Write word of zeros
        nop
2:
        sub.f   r3, r3, 0xff            ; Decrement word count
        jp      .Lbss_loop

#else   /* __ARC601__ */

; Startup code for the ARC600, ARC700 and ARCv2 processors
; NOTE:  The following restrictions apply on zero overhead loops (other
; restrictions are not pertinent to this code)
; - loop end should be 4 instruction words away from the lp_count setting
;   instruction
; - loop body should have at least two instruction words
__start:
#if defined (__ARCHS__)
        ; Allow unaligned accesses.
        lr      r2, [0xA]
        bset    r2, r2, 19
        flag    r2
#endif

#if defined (__ARC_CODE_DENSITY__)
        ;; Initialize jli_base
        sr      @__JLI_TABLE__,[jli_base]
#endif
        mov     gp, @__SDATA_BEGIN__
        mov_s   r2, @__sbss_start       ; r2 = start of the bss section
        sub     r3, @_end, r2           ; r3 = size of the bss section in bytes
        ; set up the loop counter register to the size (in words) of the bss section
#if defined (__ARC_BARREL_SHIFTER__)
        asr.f        lp_count, r3, 2
#else
        asr_s        r13, r3
        asr.f        lp_count, r13
#endif
#if defined (__ARC600__)
        ; loop to zero out the bss.  Enter loop only if lp_count != 0
        lpnz    @.Lend_zbss
        add     r3, pcl, 20
        sr      r3, [2]                 ; LP_END
        ; initialize stack pointer, and this instruction has 2 words
        mov     sp, @__stack_top
        mov_s   r3, 0
        st.ab   r3, [r2, 4]             ; zero out the word
.Lend_zbss:
#else
        mov     sp, @__stack_top        ; initialize stack pointer
        mov_s   r3,0
        ; loop to zero out the bss.  Enter loop only if lp_count != 0
        lpnz    @.Lend_zbss
        st.ab   r3,[r2, 4]              ; zero out the word
        nop
.Lend_zbss:
#endif

#endif /* !__ARC601__ */

; Some  targets use the .init and .fini sections to create constructors and
; destructors, and for these targets we need to call the _init function and
; arrange for _fini to be called at program exit.
        mov_s   r13, r0
        mov_s   r14, r1
        ; calling atexit drags in malloc, so instead poke the function
        ; address directly into the reent structure
        ld      r1, [gp, @_impure_ptr@sda]
        mov_s   r0, @_fini
        add     r1, r1, 0x14c           ; &_GLOBAL_REENT->atexit0
        st      r1, [r1, -4]            ; _GLOBAL_REENT->atexit
        st_s    r0, [r1, 8]             ; _GLOBAL_REENT->atexit0._fns[0]
        mov_s   r0, 1
        st_s    r0, [r1, 4]             ; _GLOBAL_REENT->atexit0._ind
; branch to _init
#if defined (__ARCEM__) || defined (__ARCHS__)
        jl      @_init
#else
        bl      @_init
#endif /* __ARCEM__ || __ARCHS__ */

#ifdef PROFILE_SUPPORT /* Defined in gcrt0.S.  */
        mov     r0,@__start
        mov     r1,@_etext
        jl      @_monstartup
#endif /* PROFILE_SUPPORT */

        mov_s   r0, r13
        mov_s   r1, r14
; branch to main
#if defined (__ARCEM__) || defined (__ARCHS__)
        mov     fp,0                    ; initialize frame pointer
        jl      @main
#else
        bl.d    @main
        mov     fp, 0                   ; initialize frame pointer
#endif /* __ARCEM__ || __ARCHS__ */

#ifdef PROFILE_SUPPORT
        mov     r13, r0         ; Save return code
        jl      @_mcleanup
        mov     r0, r13
#endif /* PROFILE_SUPPORT */

        ; r0 contains exit code
        j       @exit

.section .text._exit_halt,"ax",@progbits
.global  _exit_halt
.type    _exit_halt, @function
        .align 4
_exit_halt:
        ; r0 contains exit code
        flag    1
#if defined (__ARC600__) || defined (__ARC700__)
        ; ARCompact requires 3 nops after flag 1
        nop
        nop
        nop
#endif
        b       @_exit_halt
.balign 4