Danila Fedorin
cf6f353f20
ARM and x86_64 require "real" pointers to be sign-extended in their top bits. This means a working pointer is guaranteed to have either "11" as leading bits, or "00". So, to tag a "fake" pointer which is an unboxed 32-bit integer, we simply toggle the leading bit.
273 lines
7.4 KiB
C
273 lines
7.4 KiB
C
#include <bits/stdint-intn.h>
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#include <stdint.h>
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#include <assert.h>
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#include <memory.h>
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#include <stdio.h>
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#include "runtime.h"
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#define TOGGLE_MARK(n) ((uint64_t) n ^ ((uint64_t) 1 << 63))
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#define IS_MARKED(n) ((((uint64_t) n) ^ ((uint64_t) n << 1)) & ((uint64_t) 1 << 63))
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struct node_base* alloc_node() {
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struct node_base* new_node = malloc(sizeof(struct node_app));
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new_node->gc_next = NULL;
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new_node->gc_reachable = 0;
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assert(new_node != NULL);
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return new_node;
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}
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struct node_app* alloc_app(struct node_base* l, struct node_base* r) {
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struct node_app* node = (struct node_app*) alloc_node();
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node->base.tag = NODE_APP;
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node->left = l;
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node->right = r;
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return node;
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}
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struct node_num* alloc_num(int32_t n) {
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return (struct node_num*) TOGGLE_MARK(n);
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}
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struct node_global* alloc_global(void (*f)(struct gmachine*), int32_t a) {
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struct node_global* node = (struct node_global*) alloc_node();
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node->base.tag = NODE_GLOBAL;
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node->arity = a;
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node->function = f;
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return node;
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}
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struct node_ind* alloc_ind(struct node_base* n) {
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struct node_ind* node = (struct node_ind*) alloc_node();
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node->base.tag = NODE_IND;
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node->next = n;
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return node;
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}
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void free_node_direct(struct node_base* n) {
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if(n->tag == NODE_DATA) {
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free(((struct node_data*) n)->array);
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}
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}
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void gc_visit_node(struct node_base* n) {
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if(IS_MARKED(n) || n->gc_reachable) return;
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n->gc_reachable = 1;
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if(n->tag == NODE_APP) {
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struct node_app* app = (struct node_app*) n;
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gc_visit_node(app->left);
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gc_visit_node(app->right);
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} if(n->tag == NODE_IND) {
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struct node_ind* ind = (struct node_ind*) n;
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gc_visit_node(ind->next);
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} if(n->tag == NODE_DATA) {
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struct node_data* data = (struct node_data*) n;
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struct node_base** to_visit = data->array;
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while(*to_visit) {
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gc_visit_node(*to_visit);
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to_visit++;
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}
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}
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}
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void stack_init(struct stack* s) {
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s->size = 4;
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s->count = 0;
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s->data = malloc(sizeof(*s->data) * s->size);
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assert(s->data != NULL);
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}
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void stack_free(struct stack* s) {
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free(s->data);
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}
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void stack_push(struct stack* s, struct node_base* n) {
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while(s->count >= s->size) {
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s->data = realloc(s->data, sizeof(*s->data) * (s->size *= 2));
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assert(s->data != NULL);
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}
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s->data[s->count++] = n;
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}
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struct node_base* stack_pop(struct stack* s) {
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assert(s->count > 0);
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return s->data[--s->count];
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}
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struct node_base* stack_peek(struct stack* s, size_t o) {
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assert(s->count > o);
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return s->data[s->count - o - 1];
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}
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void stack_popn(struct stack* s, size_t n) {
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assert(s->count >= n);
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s->count -= n;
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}
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void gmachine_init(struct gmachine* g) {
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stack_init(&g->stack);
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g->gc_nodes = NULL;
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g->gc_node_count = 0;
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g->gc_node_threshold = 128;
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}
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void gmachine_free(struct gmachine* g) {
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stack_free(&g->stack);
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struct node_base* to_free = g->gc_nodes;
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struct node_base* next;
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while(to_free) {
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next = to_free->gc_next;
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free_node_direct(to_free);
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free(to_free);
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to_free = next;
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}
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}
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void gmachine_slide(struct gmachine* g, size_t n) {
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assert(g->stack.count > n);
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g->stack.data[g->stack.count - n - 1] = g->stack.data[g->stack.count - 1];
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g->stack.count -= n;
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}
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void gmachine_update(struct gmachine* g, size_t o) {
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assert(g->stack.count > o + 1);
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struct node_ind* ind =
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(struct node_ind*) g->stack.data[g->stack.count - o - 2];
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ind->base.tag = NODE_IND;
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ind->next = g->stack.data[g->stack.count -= 1];
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}
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void gmachine_alloc(struct gmachine* g, size_t o) {
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while(o--) {
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stack_push(&g->stack,
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gmachine_track(g, (struct node_base*) alloc_ind(NULL)));
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}
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}
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void gmachine_pack(struct gmachine* g, size_t n, int8_t t) {
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assert(g->stack.count >= n);
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struct node_base** data = malloc(sizeof(*data) * (n + 1));
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assert(data != NULL);
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memcpy(data, &g->stack.data[g->stack.count - n], n * sizeof(*data));
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data[n] = NULL;
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struct node_data* new_node = (struct node_data*) alloc_node();
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new_node->array = data;
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new_node->base.tag = NODE_DATA;
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new_node->tag = t;
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stack_popn(&g->stack, n);
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stack_push(&g->stack, gmachine_track(g, (struct node_base*) new_node));
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}
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void gmachine_split(struct gmachine* g, size_t n) {
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struct node_data* node = (struct node_data*) stack_pop(&g->stack);
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for(size_t i = 0; i < n; i++) {
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stack_push(&g->stack, node->array[i]);
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}
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}
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struct node_base* gmachine_track(struct gmachine* g, struct node_base* b) {
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if(IS_MARKED(b)) return b;
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g->gc_node_count++;
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b->gc_next = g->gc_nodes;
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g->gc_nodes = b;
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if(g->gc_node_count >= g->gc_node_threshold) {
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uint64_t nodes_before = g->gc_node_count;
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gc_visit_node(b);
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gmachine_gc(g);
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g->gc_node_threshold = g->gc_node_count * 2;
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}
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return b;
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}
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void gmachine_gc(struct gmachine* g) {
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for(size_t i = 0; i < g->stack.count; i++) {
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gc_visit_node(g->stack.data[i]);
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}
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struct node_base** head_ptr = &g->gc_nodes;
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while(*head_ptr) {
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if((*head_ptr)->gc_reachable) {
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(*head_ptr)->gc_reachable = 0;
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head_ptr = &(*head_ptr)->gc_next;
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} else {
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struct node_base* to_free = *head_ptr;
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*head_ptr = to_free->gc_next;
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free_node_direct(to_free);
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free(to_free);
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g->gc_node_count--;
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}
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}
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}
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void unwind(struct gmachine* g) {
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struct stack* s = &g->stack;
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while(1) {
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struct node_base* peek = stack_peek(s, 0);
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if(IS_MARKED(peek)) {
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break;
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} else if(peek->tag == NODE_APP) {
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struct node_app* n = (struct node_app*) peek;
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stack_push(s, n->left);
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} else if(peek->tag == NODE_GLOBAL) {
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struct node_global* n = (struct node_global*) peek;
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assert(s->count > n->arity);
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for(size_t i = 1; i <= n->arity; i++) {
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s->data[s->count - i]
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= ((struct node_app*) s->data[s->count - i - 1])->right;
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}
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n->function(g);
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} else if(peek->tag == NODE_IND) {
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struct node_ind* n = (struct node_ind*) peek;
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stack_pop(s);
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stack_push(s, n->next);
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} else {
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break;
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}
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}
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}
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extern void f_main(struct gmachine* s);
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void print_node(struct node_base* n) {
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if(IS_MARKED(n)) {
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printf("%d", (int32_t) n);
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} else if(n->tag == NODE_APP) {
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struct node_app* app = (struct node_app*) n;
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print_node(app->left);
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putchar(' ');
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print_node(app->right);
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} else if(n->tag == NODE_DATA) {
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printf("(Packed)");
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} else if(n->tag == NODE_GLOBAL) {
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struct node_global* global = (struct node_global*) n;
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printf("(Global: %p)", global->function);
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} else if(n->tag == NODE_IND) {
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print_node(((struct node_ind*) n)->next);
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}
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}
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int main(int argc, char** argv) {
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struct gmachine gmachine;
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struct node_global* first_node = alloc_global(f_main, 0);
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struct node_base* result;
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gmachine_init(&gmachine);
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gmachine_track(&gmachine, (struct node_base*) first_node);
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stack_push(&gmachine.stack, (struct node_base*) first_node);
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unwind(&gmachine);
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result = stack_pop(&gmachine.stack);
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printf("Result: ");
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print_node(result);
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putchar('\n');
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gmachine_free(&gmachine);
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}
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