Subversion Repositories openrisc_2011-10-31

/* Assembly functions for libgcc2.
   Copyright (C) 2001, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
   Contributed by Bob Wilson (bwilson@tensilica.com) at Tensilica.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#include "xtensa-config.h"

/* __xtensa_libgcc_window_spill: This function flushes out all but the
   current register window.  This is used to set up the stack so that
   arbitrary frames can be accessed.  */

        .align  4
        .global __xtensa_libgcc_window_spill
        .type   __xtensa_libgcc_window_spill,@function
__xtensa_libgcc_window_spill:
        entry   sp, 32
        movi    a2, 0
        syscall
        retw
        .size   __xtensa_libgcc_window_spill, .-__xtensa_libgcc_window_spill


/* __xtensa_nonlocal_goto: This code does all the hard work of a
   nonlocal goto on Xtensa.  It is here in the library to avoid the
   code size bloat of generating it in-line.  There are two
   arguments:

        a2 = frame pointer for the procedure containing the label
        a3 = goto handler address

  This function never returns to its caller but instead goes directly
  to the address of the specified goto handler.  */

        .align  4
        .global __xtensa_nonlocal_goto
        .type   __xtensa_nonlocal_goto,@function
__xtensa_nonlocal_goto:
        entry   sp, 32

        /* Flush registers.  */
        mov     a5, a2
        movi    a2, 0
        syscall
        mov     a2, a5

        /* Because the save area for a0-a3 is stored one frame below
           the one identified by a2, the only way to restore those
           registers is to unwind the stack.  If alloca() were never
           called, we could just unwind until finding the sp value
           matching a2.  However, a2 is a frame pointer, not a stack
           pointer, and may not be encountered during the unwinding.
           The solution is to unwind until going _past_ the value
           given by a2.  This involves keeping three stack pointer
           values during the unwinding:

                next = sp of frame N-1
                cur = sp of frame N
                prev = sp of frame N+1

           When next > a2, the desired save area is stored relative
           to prev.  At this point, cur will be the same as a2
           except in the alloca() case.

           Besides finding the values to be restored to a0-a3, we also
           need to find the current window size for the target
           function.  This can be extracted from the high bits of the
           return address, initially in a0.  As the unwinding
           proceeds, the window size is taken from the value of a0
           saved _two_ frames below the current frame.  */

        addi    a5, sp, -16     /* a5 = prev - save area */
        l32i    a6, a5, 4
        addi    a6, a6, -16     /* a6 = cur - save area */
        mov     a8, a0          /* a8 = return address (for window size) */
        j       .Lfirstframe

.Lnextframe:
        l32i    a8, a5, 0       /* next return address (for window size) */
        mov     a5, a6          /* advance prev */
        addi    a6, a7, -16     /* advance cur */
.Lfirstframe:
        l32i    a7, a6, 4       /* a7 = next */
        bgeu    a2, a7, .Lnextframe

        /* At this point, prev (a5) points to the save area with the saved
           values of a0-a3.  Copy those values into the save area at the
           current sp so they will be reloaded when the return from this
           function underflows.  We don't have to worry about exceptions
           while updating the current save area, because the windows have
           already been flushed.  */

        addi    a4, sp, -16     /* a4 = save area of this function */
        l32i    a6, a5, 0
        l32i    a7, a5, 4
        s32i    a6, a4, 0
        s32i    a7, a4, 4
        l32i    a6, a5, 8
        l32i    a7, a5, 12
        s32i    a6, a4, 8
        s32i    a7, a4, 12

        /* Set return address to goto handler.  Use the window size bits
           from the return address two frames below the target.  */
        extui   a8, a8, 30, 2   /* get window size from return addr. */
        slli    a3, a3, 2       /* get goto handler addr. << 2 */
        ssai    2
        src     a0, a8, a3      /* combine them with a funnel shift */

        retw
        .size   __xtensa_nonlocal_goto, .-__xtensa_nonlocal_goto


/* __xtensa_sync_caches: This function is called after writing a trampoline
   on the stack to force all the data writes to memory and invalidate the
   instruction cache. a2 is the address of the new trampoline.

   After the trampoline data is written out, it must be flushed out of
   the data cache into memory.  We use DHWB in case we have a writeback
   cache.  At least one DHWB instruction is needed for each data cache
   line which may be touched by the trampoline.  An ISYNC instruction
   must follow the DHWBs.

   We have to flush the i-cache to make sure that the new values get used.
   At least one IHI instruction is needed for each i-cache line which may
   be touched by the trampoline.  An ISYNC instruction is also needed to
   make sure that the modified instructions are loaded into the instruction
   fetch buffer.  */

/* Use the maximum trampoline size.  Flushing a bit extra is OK.  */
#define TRAMPOLINE_SIZE 60

        .text
        .align  4
        .global __xtensa_sync_caches
        .type   __xtensa_sync_caches,@function
__xtensa_sync_caches:
        entry   sp, 32
#if XCHAL_DCACHE_SIZE > 0
        /* Flush the trampoline from the data cache.  */
        extui   a4, a2, 0, XCHAL_DCACHE_LINEWIDTH
        addi    a4, a4, TRAMPOLINE_SIZE
        addi    a4, a4, (1 << XCHAL_DCACHE_LINEWIDTH) - 1
        srli    a4, a4, XCHAL_DCACHE_LINEWIDTH
        mov     a3, a2
.Ldcache_loop:
        dhwb    a3, 0
        addi    a3, a3, (1 << XCHAL_DCACHE_LINEWIDTH)
        addi    a4, a4, -1
        bnez    a4, .Ldcache_loop
        isync
#endif
#if XCHAL_ICACHE_SIZE > 0
        /* Invalidate the corresponding lines in the instruction cache.  */
        extui   a4, a2, 0, XCHAL_ICACHE_LINEWIDTH
        addi    a4, a4, TRAMPOLINE_SIZE
        addi    a4, a4, (1 << XCHAL_ICACHE_LINEWIDTH) - 1
        srli    a4, a4, XCHAL_ICACHE_LINEWIDTH
.Licache_loop:
        ihi     a2, 0
        addi    a2, a2, (1 << XCHAL_ICACHE_LINEWIDTH)
        addi    a4, a4, -1
        bnez    a4, .Licache_loop
#endif
        isync
        retw
        .size   __xtensa_sync_caches, .-__xtensa_sync_caches