unix: Implement garbage collection support.

unix/Makefile

@@ -35,6 +35,7 @@ endif
 # source files
 SRC_C = \
 	main.c \
+	gccollect.c \
 	file.c \
 	socket.c \
 	$(SRC_MOD)

unix/gccollect.c

+#include <stdint.h>
+#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
+
+void gc_collect(void) {
+    gc_collect_start();
+    // this traces .data and .bss sections
+    extern char __bss_start, _end;
+    //printf(".bss: %p-%p\n", &__bss_start, &_end);
+    gc_collect_root((void**)&__bss_start, ((uint32_t)&_end - (uint32_t)&__bss_start) / sizeof(uint32_t));
+    regs_t regs;
+    gc_helper_get_regs(regs);
+    // GC stack (and regs because we captured them)
+    gc_collect_root((void**)&regs, ((uint32_t)stack_top - (uint32_t)&regs) / sizeof(uint32_t));
+    gc_collect_end();
+
+    if (0) {
+        // print GC info
+        gc_info_t info;
+        gc_info(&info);
+        printf("GC: total: " UINT_FMT ", used: " UINT_FMT ", free: " UINT_FMT "\n", info.total, info.used, info.free);
+        printf(" No. of 1-blocks: " UINT_FMT ", 2-blocks: " UINT_FMT ", max blk sz: " UINT_FMT "\n",
+               info.num_1block, info.num_2block, info.max_block);
+    }
+}
+
+#endif //MICROPY_ENABLE_GC

unix/main.c

@@ -15,12 +15,20 @@
 #include "runtime0.h"
 #include "runtime.h"
 #include "repl.h"
+#include "gc.h"
 
 #if MICROPY_USE_READLINE
 #include <readline/readline.h>
 #include <readline/history.h>
 #endif
 
+// Heap size of GC heap (if enabled)
+// TODO: allow to specify on command line
+#define HEAP_SIZE 128*1024
+
+// Stack top at the start of program
+void *stack_top;
+
 extern const mp_obj_fun_native_t mp_builtin_open_obj;
 void file_init();
 void microsocket_init();
@@ -217,7 +225,24 @@ mp_obj_t qstr_info(void) {
     return mp_const_none;
 }
 
+#if MICROPY_ENABLE_GC
+// TODO: this doesn't belong here
+static mp_obj_t pyb_gc(void) {
+    gc_collect();
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_0(pyb_gc_obj, pyb_gc);
+#endif
+
 int main(int argc, char **argv) {
+    volatile int stack_dummy;
+    stack_top = (void*)&stack_dummy;
+
+#if MICROPY_ENABLE_GC
+    char *heap = malloc(HEAP_SIZE);
+    gc_init(heap, heap + HEAP_SIZE);
+#endif
+
     qstr_init();
     rt_init();
 
@@ -263,6 +288,9 @@ int main(int argc, char **argv) {
     rt_store_name(qstr_from_str("test"), test_obj_new(42));
     rt_store_name(qstr_from_str("mem_info"), rt_make_function_n(0, mem_info));
     rt_store_name(qstr_from_str("qstr_info"), rt_make_function_n(0, qstr_info));
+#if MICROPY_ENABLE_GC
+    rt_store_name(qstr_from_str("gc"), (mp_obj_t)&pyb_gc_obj);
+#endif
 
     file_init();
     microsocket_init();