micropython/py/nlrthumb.c

/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2013-2017 Damien P. George
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "py/mpstate.h"

#if MICROPY_NLR_THUMB

#undef nlr_push

// We only need the functions here if we are on arm/thumb, and we are not
// using setjmp/longjmp.
//
// For reference, arm/thumb callee save regs are:
//      r4-r11, r13=sp

__attribute__((naked)) unsigned int nlr_push(nlr_buf_t *nlr) {

    // If you get a linker error here, indicating that a relocation doesn't
    // fit, try the following (in that order):
    //
    // 1. Ensure that nlr.o nlrthumb.o are linked closely together, i.e.
    //    there aren't too many other files between them in the linker list
    //    (PY_CORE_O_BASENAME in py/py.mk)
    // 2. Set -DMICROPY_NLR_THUMB_USE_LONG_JUMP=1 during the build
    //
    __asm volatile (
        "str    r4, [r0, #12]       \n" // store r4 into nlr_buf
        "str    r5, [r0, #16]       \n" // store r5 into nlr_buf
        "str    r6, [r0, #20]       \n" // store r6 into nlr_buf
        "str    r7, [r0, #24]       \n" // store r7 into nlr_buf

        #if !defined(__thumb2__)
        "mov    r1, r8              \n"
        "str    r1, [r0, #28]       \n" // store r8 into nlr_buf
        "mov    r1, r9              \n"
        "str    r1, [r0, #32]       \n" // store r9 into nlr_buf
        "mov    r1, r10             \n"
        "str    r1, [r0, #36]       \n" // store r10 into nlr_buf
        "mov    r1, r11             \n"
        "str    r1, [r0, #40]       \n" // store r11 into nlr_buf
        "mov    r1, r13             \n"
        "str    r1, [r0, #44]       \n" // store r13=sp into nlr_buf
        "mov    r1, lr              \n"
        "str    r1, [r0, #8]        \n" // store lr into nlr_buf
        #else
        "str    r8, [r0, #28]       \n" // store r8 into nlr_buf
        "str    r9, [r0, #32]       \n" // store r9 into nlr_buf
        "str    r10, [r0, #36]      \n" // store r10 into nlr_buf
        "str    r11, [r0, #40]      \n" // store r11 into nlr_buf
        "str    r13, [r0, #44]      \n" // store r13=sp into nlr_buf
        #if MICROPY_NLR_NUM_REGS == 16
        "vstr   d8, [r0, #48]       \n" // store s16-s17 into nlr_buf
        "vstr   d9, [r0, #56]       \n" // store s18-s19 into nlr_buf
        "vstr   d10, [r0, #64]      \n" // store s20-s21 into nlr_buf
        #endif
        "str    lr, [r0, #8]        \n" // store lr into nlr_buf
        #endif

        #if MICROPY_NLR_THUMB_USE_LONG_JUMP
        "ldr    r1, nlr_push_tail_var \n"
        "bx     r1                  \n" // do the rest in C
        ".align 2                   \n"
        "nlr_push_tail_var: .word nlr_push_tail \n"
        #else
        #if defined(__APPLE__) || defined(__MACH__)
        "b      _nlr_push_tail      \n" // do the rest in C
        #else
        "b      nlr_push_tail       \n" // do the rest in C
        #endif
        #endif
        );

    #if !defined(__clang__) && defined(__GNUC__) && (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8))
    // Older versions of gcc give an error when naked functions don't return a value
    // Additionally exclude Clang as it also defines __GNUC__ but doesn't need this statement
    return 0;
    #endif
}

MP_NORETURN void nlr_jump(void *val) {
    MP_NLR_JUMP_HEAD(val, top)

    __asm volatile (
        "mov    r0, %0              \n" // r0 points to nlr_buf
        "ldr    r4, [r0, #12]       \n" // load r4 from nlr_buf
        "ldr    r5, [r0, #16]       \n" // load r5 from nlr_buf
        "ldr    r6, [r0, #20]       \n" // load r6 from nlr_buf
        "ldr    r7, [r0, #24]       \n" // load r7 from nlr_buf

        #if !defined(__thumb2__)
        "ldr    r1, [r0, #28]       \n" // load r8 from nlr_buf
        "mov    r8, r1              \n"
        "ldr    r1, [r0, #32]       \n" // load r9 from nlr_buf
        "mov    r9, r1              \n"
        "ldr    r1, [r0, #36]       \n" // load r10 from nlr_buf
        "mov    r10, r1             \n"
        "ldr    r1, [r0, #40]       \n" // load r11 from nlr_buf
        "mov    r11, r1             \n"
        "ldr    r1, [r0, #44]       \n" // load r13=sp from nlr_buf
        "mov    r13, r1             \n"
        "ldr    r1, [r0, #8]        \n" // load lr from nlr_buf
        "mov    lr, r1              \n"
        #else
        "ldr    r8, [r0, #28]       \n" // load r8 from nlr_buf
        "ldr    r9, [r0, #32]       \n" // load r9 from nlr_buf
        "ldr    r10, [r0, #36]      \n" // load r10 from nlr_buf
        "ldr    r11, [r0, #40]      \n" // load r11 from nlr_buf
        "ldr    r13, [r0, #44]      \n" // load r13=sp from nlr_buf
        #if MICROPY_NLR_NUM_REGS == 16
        "vldr   d8, [r0, #48]       \n" // load s16-s17 from nlr_buf
        "vldr   d9, [r0, #56]       \n" // load s18-s19 from nlr_buf
        "vldr   d10, [r0, #64]      \n" // load s20-s21 from nlr_buf
        #endif
        "ldr    lr, [r0, #8]        \n" // load lr from nlr_buf
        #endif
        "movs   r0, #1              \n" // return 1, non-local return
        "bx     lr                  \n" // return
        :                           // output operands
        : "r" (top)                 // input operands
        : "memory"                  // clobbered registers
        );

    MP_UNREACHABLE
}

#endif // MICROPY_NLR_THUMB