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Don't make const heap objects roots #223

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Don't make const heap objects roots #223

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34 changes: 29 additions & 5 deletions runtime.c
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Original file line number Diff line number Diff line change
Expand Up @@ -215,6 +215,20 @@ bool in_const_heap(struct gc_obj* obj) {
(uword)obj < (uword)__stop_const_heap;
}

static struct object* transport(struct gc_obj* from, struct gc_heap* heap) {
assert(!in_const_heap(from));
struct gc_obj* to = is_forwarded(from) ? forwarded(from) : copy(heap, from);
return heap_tag((uintptr_t)to);
}

void visit_root(struct object** pointer, struct gc_heap* heap) {
if (!is_heap_object(*pointer)) {
return;
}
struct gc_obj* from = as_heap_object(*pointer);
*pointer = transport(from, heap);
}

void visit_field(struct object** pointer, struct gc_heap* heap) {
if (!is_heap_object(*pointer)) {
return;
Expand All @@ -223,8 +237,7 @@ void visit_field(struct object** pointer, struct gc_heap* heap) {
if (in_const_heap(from)) {
return;
}
struct gc_obj* to = is_forwarded(from) ? forwarded(from) : copy(heap, from);
*pointer = heap_tag((uintptr_t)to);
*pointer = transport(from, heap);
}

static bool in_heap(struct gc_heap* heap, struct gc_obj* obj) {
Expand Down Expand Up @@ -259,7 +272,7 @@ static NEVER_INLINE void heap_verify(struct gc_heap* heap) {
void collect_no_verify(struct gc_heap* heap) {
flip(heap);
uintptr_t scan = heap->hp;
trace_roots(heap, visit_field);
trace_roots(heap, visit_root);
while (scan < heap->hp) {
struct gc_obj* obj = (struct gc_obj*)scan;
scan += align_size(trace_heap_object(obj, heap, visit_field));
Expand Down Expand Up @@ -683,8 +696,19 @@ void pop_handles(void* local_handles) {
struct handle_scope local_handles __attribute__((__cleanup__(pop_handles))); \
local_handles.base = handles;
#define GC_PROTECT(x) \
assert(handles != handles_end); \
(*handles++) = (struct object**)(&x)
do { \
/* TODO(max): Determine if it's worth it to have this fast path or if it's \
* just cluttering the code and should be done in a more advanced \
* compiler. */ \
if (!is_heap_object(x)) { \
break; \
} \
if (in_const_heap(as_heap_object(x))) { \
break; \
} \
assert(handles != handles_end); \
(*handles++) = (struct object**)(&x); \
} while (0)
#define GC_HANDLE(type, name, val) \
type name = val; \
GC_PROTECT(name)
Expand Down
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