/*
            Copyright Oliver Kowalke 2009.
   Distributed under the Boost Software License, Version 1.0.
      (See accompanying file LICENSE_1_0.txt or copy at
          http://www.boost.org/LICENSE_1_0.txt)
*/

/*******************************************************
 *                                                     *
 *  -------------------------------------------------  *
 *  |  0  |  4  |  8  |  12 |  16 |  20 |  24 |  28 |  *
 *  -------------------------------------------------  *
 *  |bchai|hiddn|   fpscr   |  PC |  CR | R14 | R15 |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  32 |  36 |  40 |  44 |  48 |  52 |  56 |  60 |  *
 *  -------------------------------------------------  *
 *  | R16 | R17 | R18 | R19 | R20 | R21 | R22 | R23 |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  64 |  68 |  72 |  76 |  80 |  84 |  88 |  92 |  *
 *  -------------------------------------------------  *
 *  | R24 | R25 | R26 | R27 | R28 | R29 | R30 | R31 |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  |  96 | 100 | 104 | 108 | 112 | 116 | 120 | 124 |  *
 *  -------------------------------------------------  *
 *  |    F14    |    F15    |    F16    |    F17    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  | 128 | 132 | 136 | 140 | 144 | 148 | 152 | 156 |  *
 *  -------------------------------------------------  *
 *  |    F18    |    F19    |    F20    |    F21    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  | 160 | 164 | 168 | 172 | 176 | 180 | 184 | 188 |  *
 *  -------------------------------------------------  *
 *  |    F22    |    F23    |    F24    |    F25    |  *
 *  -------------------------------------------------  *
 *  -------------------------------------------------  *
 *  | 192 | 196 | 200 | 204 | 208 | 212 | 216 | 220 |  *
 *  -------------------------------------------------  *
 *  |    F26    |    F27    |    F28    |    F29    |  *
 *  -------------------------------------------------  *
 *  ------------------------|------------              *
 *  | 224 | 228 | 232 | 236 | 240 | 244 |              *
 *  ------------------------|------------              *
 *  |    F30    |    F31    |bchai|  LR |              *
 *  ------------------------|------------              *
 *                                                     *
 *******************************************************/

.file "ontop_ppc32_sysv_elf_gas.S"
.text
.globl ontop_fcontext
.align 2
.type ontop_fcontext,@function
ontop_fcontext:
    # Linux: ontop_fcontext( hidden transfer_t * R3, R4, R5, R6)
    # Other: transfer_t R3:R4 = jump_fcontext( R3, R4, R5)

    mflr  %r0  # return address from LR
    mffs  %f0  # FPSCR
    mfcr  %r8  # condition register

    stwu  %r1, -240(%r1)  # allocate stack space, R1 % 16 == 0
    stw   %r0, 244(%r1)   # save LR in caller's frame

#ifdef __linux__
    stw   %r3, 4(%r1)   # hidden pointer
#endif

    stfd  %f0, 8(%r1)   # FPSCR
    stw   %r0, 16(%r1)  # LR as PC
    stw   %r8, 20(%r1)  # CR

    # Save registers R14 to R31.
    # Don't change R2, the thread-local storage pointer.
    # Don't change R13, the small data pointer.
    stw   %r14, 24(%r1)
    stw   %r15, 28(%r1)
    stw   %r16, 32(%r1)
    stw   %r17, 36(%r1)
    stw   %r18, 40(%r1)
    stw   %r19, 44(%r1)
    stw   %r20, 48(%r1)
    stw   %r21, 52(%r1)
    stw   %r22, 56(%r1)
    stw   %r23, 60(%r1)
    stw   %r24, 64(%r1)
    stw   %r25, 68(%r1)
    stw   %r26, 72(%r1)
    stw   %r27, 76(%r1)
    stw   %r28, 80(%r1)
    stw   %r29, 84(%r1)
    stw   %r30, 88(%r1)
    stw   %r31, 92(%r1)

    # Save registers F14 to F31 in slots with 8-byte alignment.
    # 4-byte alignment may stall the pipeline of some processors.
    # Less than 4 may cause alignment traps.
    stfd  %f14, 96(%r1)
    stfd  %f15, 104(%r1)
    stfd  %f16, 112(%r1)
    stfd  %f17, 120(%r1)
    stfd  %f18, 128(%r1)
    stfd  %f19, 136(%r1)
    stfd  %f20, 144(%r1)
    stfd  %f21, 152(%r1)
    stfd  %f22, 160(%r1)
    stfd  %f23, 168(%r1)
    stfd  %f24, 176(%r1)
    stfd  %f25, 184(%r1)
    stfd  %f26, 192(%r1)
    stfd  %f27, 200(%r1)
    stfd  %f28, 208(%r1)
    stfd  %f29, 216(%r1)
    stfd  %f30, 224(%r1)
    stfd  %f31, 232(%r1)

    # store RSP (pointing to context-data) in R7/R6
    # restore RSP (pointing to context-data) from R4/R3
#ifdef __linux__
    mr   %r7, %r1
    mr   %r1, %r4
    lwz  %r3, 4(%r1)   # hidden pointer
#else
    mr   %r6, %r1
    mr   %r1, %r3
#endif

    # ignore PC at 16(%r1)
    lfd  %f0, 8(%r1)   # FPSCR
    lwz  %r8, 20(%r1)  # CR

    mtfsf  0xff, %f0   # restore FPSCR
    mtcr   %r8         # restore CR

    # restore R14 to R31
    lwz  %r14, 24(%r1)
    lwz  %r15, 28(%r1)
    lwz  %r16, 32(%r1)
    lwz  %r17, 36(%r1)
    lwz  %r18, 40(%r1)
    lwz  %r19, 44(%r1)
    lwz  %r20, 48(%r1)
    lwz  %r21, 52(%r1)
    lwz  %r22, 56(%r1)
    lwz  %r23, 60(%r1)
    lwz  %r24, 64(%r1)
    lwz  %r25, 68(%r1)
    lwz  %r26, 72(%r1)
    lwz  %r27, 76(%r1)
    lwz  %r28, 80(%r1)
    lwz  %r29, 84(%r1)
    lwz  %r30, 88(%r1)
    lwz  %r31, 92(%r1)

    # restore F14 to F31
    lfd  %f14, 96(%r1)
    lfd  %f15, 104(%r1)
    lfd  %f16, 112(%r1)
    lfd  %f17, 120(%r1)
    lfd  %f18, 128(%r1)
    lfd  %f19, 136(%r1)
    lfd  %f20, 144(%r1)
    lfd  %f21, 152(%r1)
    lfd  %f22, 160(%r1)
    lfd  %f23, 168(%r1)
    lfd  %f24, 176(%r1)
    lfd  %f25, 184(%r1)
    lfd  %f26, 192(%r1)
    lfd  %f27, 200(%r1)
    lfd  %f28, 208(%r1)
    lfd  %f29, 216(%r1)
    lfd  %f30, 224(%r1)
    lfd  %f31, 232(%r1)

    # restore LR from caller's frame
    lwz   %r0, 244(%r1)
    mtlr  %r0

    # adjust stack
    addi  %r1, %r1, 240

    # see tail_ppc32_sysv_elf_gas.cpp
    # Linux: fcontext_ontop_tail( hidden transfer_t * R3, R4, R5, R6, R7)
    # Other: transfer_t R3:R4 = fcontext_ontop_tail( R3, R4, R5, R6)
    b ontop_fcontext_tail
.size ontop_fcontext, .-ontop_fcontext

/* Mark that we don't need executable stack.  */
.section .note.GNU-stack,"",%progbits
