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When vec growth results in a newly allocated (extended) buffer, copy existing elements over via element-wise copy, not flat memcpy. Introduce new vec growth glue to achieve this.

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This commit is contained in:
Roy Frostig
2010-09-03 16:18:32 -07:00
parent 1eb2a8b10b
commit 4e355aebf7
4 changed files with 221 additions and 28 deletions
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35
src/rt/rust_upcall.cpp
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@@ -384,18 +384,23 @@ upcall_new_vec(rust_task *task, size_t fill, type_desc *td) {
return v;
}
extern "C" CDECL rust_str *
extern "C" CDECL rust_vec *
upcall_vec_grow(rust_task *task,
rust_vec *v,
size_t n_bytes,
uintptr_t is_gc) {
uintptr_t *need_copy)
{
LOG_UPCALL_ENTRY(task);
rust_dom *dom = task->dom;
task->log(rust_log::UPCALL|rust_log::MEM,
"upcall vec_grow(0x%" PRIxPTR ", %" PRIdPTR
"), alloc=%" PRIdPTR ", fill=%" PRIdPTR,
v, n_bytes, v->alloc, v->fill);
task->log(rust_log::UPCALL | rust_log::MEM,
"upcall vec_grow(0x%" PRIxPTR ", %" PRIdPTR
"), alloc=%" PRIdPTR ", fill=%" PRIdPTR
", need_copy=0x%" PRIxPTR,
v, n_bytes, v->alloc, v->fill, need_copy);
*need_copy = 0;
size_t alloc = next_power_of_two(sizeof(rust_vec) + v->fill + n_bytes);
if (v->ref_count == 1) {
// Fastest path: already large enough.
@@ -414,7 +419,19 @@ upcall_vec_grow(rust_task *task,
v->alloc = alloc;
} else {
// Slowest path: make a new vec.
/**
* Slowest path: make a new vec.
*
* 1. Allocate a new rust_vec with desired additional space.
* 2. Down-ref the shared rust_vec, point to the new one instead.
* 3. Copy existing elements into the new rust_vec.
*
* Step 3 is a bit tricky. We don't know how to properly copy the
* elements in the runtime (all we have are bits in a buffer; no
* type infromation and no copy glue). What we do instead is set the
* need_copy outparam flag to indicate to our caller (vec-copy glue)
* that we need the copies performed for us.
*/
task->log(rust_log::UPCALL | rust_log::MEM, "new vec path");
void *mem = dom->malloc(alloc);
if (!mem) {
@@ -422,8 +439,8 @@ upcall_vec_grow(rust_task *task,
return NULL;
}
v->deref();
v = new (mem) rust_vec(dom, alloc, v->fill,
v->fill ? &v->data[0] : NULL);
v = new (mem) rust_vec(dom, alloc, 0, NULL);
*need_copy = 1;
}
I(dom, sizeof(rust_vec) + v->fill <= v->alloc);
return v;