text: #include <stdio.h>
  
  #include "misc.h"
  #include "mpconfig.h"
  #include "gc.h"
  
  #if MICROPY_ENABLE_GC
  
  extern void *stack_top;
  
  // We capture here callee-save registers, i.e. ones which may contain
  // interesting values held there by our callers. It doesn't make sense
  // to capture caller-saved registers, because they, well, put on the
  // stack already by the caller.
  #ifdef __x86_64__
  typedef machine_uint_t regs_t[6];
  
  void gc_helper_get_regs(regs_t arr) {
      register long rbx asm ("rbx");
      register long rbp asm ("rbp");
      register long r12 asm ("r12");
      register long r13 asm ("r13");
      register long r14 asm ("r14");
      register long r15 asm ("r15");
      arr[0] = rbx;
      arr[1] = rbp;
      arr[2] = r12;
      arr[3] = r13;
      arr[4] = r14;
      arr[5] = r15;
  }
  #endif
  
  #ifdef __i386__
  typedef machine_uint_t regs_t[4];
  
  void gc_helper_get_regs(regs_t arr) {
      register long ebx asm ("ebx");
      register long esi asm ("esi");
      register long edi asm ("edi");
      register long ebp asm ("ebp");
      arr[0] = ebx;
      arr[1] = esi;
      arr[2] = edi;
      arr[3] = ebp;
  }
  #endif
  
  #ifdef __thumb2__
  typedef machine_uint_t regs_t[10];
  
  void gc_helper_get_regs(regs_t arr) {
      register long r4 asm ("r4");
      register long r5 asm ("r5");
      register long r6 asm ("r6");
      register long r7 asm ("r7");
      register long r8 asm ("r8");
      register long r9 asm ("r9");
      register long r10 asm ("r10");
      register long r11 asm ("r11");
      register long r12 asm ("r12");
      register long r13 asm ("r13");
      arr[0] = r4;
      arr[1] = r5;
      arr[2] = r6;
      arr[3] = r7;
      arr[4] = r8;
      arr[5] = r9;
      arr[6] = r10;
      arr[7] = r11;
      arr[8] = r12;
      arr[9] = r13;
  }
  #endif
  
  void gc_collect(void) {
      //gc_dump_info();
  
      gc_collect_start();
      // this traces the .bss section
  #ifdef __CYGWIN__
  #define BSS_START __bss_start__
  #else
  #define BSS_START __bss_start
  #endif
      extern char BSS_START, _end;
      //printf(".bss: %p-%p\n", &BSS_START, &_end);
      gc_collect_root((void**)&BSS_START, ((machine_uint_t)&_end - (machine_uint_t)&BSS_START) / sizeof(machine_uint_t));
      regs_t regs;
      gc_helper_get_regs(regs);
      // GC stack (and regs because we captured them)
      gc_collect_root((void**)&regs, ((machine_uint_t)stack_top - (machine_uint_t)&regs) / sizeof(machine_uint_t));
      gc_collect_end();
  
      //printf("-----\n");
      //gc_dump_info();
  }
  
  #endif //MICROPY_ENABLE_GC
  