rt: Make the dynamic stack self-describing

Author: pcwalton

src/comp/back/upcall.rs

@@ -109,7 +109,8 @@ fn declare_upcalls(_tn: type_names, tydesc_type: TypeRef,
                  [taskptr_type, T_ptr(tydesc_type), T_ptr(T_i8()), T_i32()],
                  T_void()),
           dynastack_mark: d(~"dynastack_mark", [], T_ptr(T_i8())),
-          dynastack_alloc: d(~"dynastack_alloc", [T_size_t()], T_ptr(T_i8())),
+          dynastack_alloc: d(~"dynastack_alloc_2",
+                             [T_size_t(), T_ptr(tydesc_type)], T_ptr(T_i8())),
           dynastack_free: d(~"dynastack_free", [T_ptr(T_i8())], T_void())};
 }
 //

src/comp/middle/trans.rs

@@ -471,7 +471,8 @@ fn alloca(cx: &@block_ctxt, t: TypeRef) -> ValueRef {
     ret Alloca(new_raw_block_ctxt(cx.fcx, cx.fcx.llstaticallocas), t);
 }
 
-fn array_alloca(cx: &@block_ctxt, t: TypeRef, n: ValueRef) -> ValueRef {
+fn dynastack_alloca(cx: &@block_ctxt, t: TypeRef, n: ValueRef, ty: ty::t)
+        -> ValueRef {
     let bcx = cx;
     let dy_cx = new_raw_block_ctxt(cx.fcx, cx.fcx.lldynamicallocas);
     let lltaskptr = bcx_fcx(bcx).lltaskptr;
@@ -485,7 +486,11 @@ fn array_alloca(cx: &@block_ctxt, t: TypeRef, n: ValueRef) -> ValueRef {
 
     let dynastack_alloc = bcx_ccx(bcx).upcalls.dynastack_alloc;
     let llsz = Mul(dy_cx, C_uint(llsize_of_real(bcx_ccx(bcx), t)), n);
-    let llresult = Call(dy_cx, dynastack_alloc, [lltaskptr, llsz]);
+
+    let ti = none;
+    let lltydesc = get_tydesc(cx, ty, false, tps_normal, ti).result.val;
+
+    let llresult = Call(dy_cx, dynastack_alloc, [lltaskptr, llsz, lltydesc]);
     ret PointerCast(dy_cx, llresult, T_ptr(t));
 }
 
@@ -4868,8 +4873,10 @@ fn alloc_ty(cx: &@block_ctxt, t: ty::t) -> result {
 
         let n = size_of(llderivedtydescs_block_ctxt(bcx.fcx), t);
         bcx.fcx.llderivedtydescs = n.bcx.llbb;
-        val = array_alloca(bcx, T_i8(), n.val);
-    } else { val = alloca(bcx, type_of(bcx_ccx(cx), cx.sp, t)); }
+        val = dynastack_alloca(bcx, T_i8(), n.val, t);
+    } else {
+        val = alloca(bcx, type_of(bcx_ccx(cx), cx.sp, t));
+    }
     // NB: since we've pushed all size calculations in this
     // function up to the alloca block, we actually return the
     // block passed into us unmodified; it doesn't really

src/comp/middle/trans_ivec.rs

@@ -5,7 +5,7 @@ import lib::llvm::llvm::{ValueRef, TypeRef};
 import back::abi;
 import trans::{call_memmove, trans_shared_malloc, llsize_of,
                type_of_or_i8, incr_ptr, INIT, copy_val, load_if_immediate,
-               alloca, array_alloca, size_of, llderivedtydescs_block_ctxt,
+               alloca, size_of, llderivedtydescs_block_ctxt,
                lazily_emit_tydesc_glue, get_tydesc, load_inbounds,
                move_val_if_temp, trans_lval, node_id_type,
                new_sub_block_ctxt, tps_normal, do_spill};

src/rt/rust_obstack.cpp

@@ -3,6 +3,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstdlib>
+#include <new>
 #include <stdint.h>
 
 #include "rust_internal.h"
@@ -18,9 +19,20 @@
 #define DPRINT(fmt,...)
 
 //const size_t DEFAULT_CHUNK_SIZE = 4096;
-const size_t DEFAULT_CHUNK_SIZE = 300000;
+const size_t DEFAULT_CHUNK_SIZE = 500000;
 const size_t DEFAULT_ALIGNMENT = 16;
 
+// A single type-tagged allocation in a chunk.
+struct rust_obstack_alloc {
+    size_t len;
+    const type_desc *tydesc;
+    uint8_t data[];
+
+    rust_obstack_alloc(size_t in_len, const type_desc *in_tydesc)
+    : len(in_len), tydesc(in_tydesc) {}
+};
+
+// A contiguous set of allocations.
 struct rust_obstack_chunk {
     rust_obstack_chunk *prev;
     size_t size;
@@ -31,22 +43,24 @@ struct rust_obstack_chunk {
     rust_obstack_chunk(rust_obstack_chunk *in_prev, size_t in_size)
     : prev(in_prev), size(in_size), alen(0) {}
 
-    void *alloc(size_t len);
+    void *alloc(size_t len, type_desc *tydesc);
     bool free(void *ptr);
+    void *mark();
 };
 
 void *
-rust_obstack_chunk::alloc(size_t len) {
+rust_obstack_chunk::alloc(size_t len, type_desc *tydesc) {
     alen = align_to(alen, DEFAULT_ALIGNMENT);
 
-    if (len > size - alen) {
+    if (sizeof(rust_obstack_alloc) + len > size - alen) {
         DPRINT("Not enough space, len=%lu!\n", len);
         assert(0);
         return NULL;    // Not enough space.
     }
-    void *result = data + alen;
-    alen += len;
-    return result;
+
+    rust_obstack_alloc *a = new(data + alen) rust_obstack_alloc(len, tydesc);
+    alen += sizeof(*a) + len;
+    return &a->data;
 }
 
 bool
@@ -59,14 +73,20 @@ rust_obstack_chunk::free(void *ptr) {
     return true;
 }
 
+void *
+rust_obstack_chunk::mark() {
+    return data + alen;
+}
+
 // Allocates the given number of bytes in a new chunk.
 void *
-rust_obstack::alloc_new(size_t len) {
-    size_t chunk_size = std::max(len, DEFAULT_CHUNK_SIZE);
+rust_obstack::alloc_new(size_t len, type_desc *tydesc) {
+    size_t chunk_size = std::max(sizeof(rust_obstack_alloc) + len,
+                                 DEFAULT_CHUNK_SIZE);
     void *ptr = task->malloc(sizeof(chunk) + chunk_size, "obstack");
     DPRINT("making new chunk at %p, len %lu\n", ptr, chunk_size);
     chunk = new(ptr) rust_obstack_chunk(chunk, chunk_size);
-    return chunk->alloc(len);
+    return chunk->alloc(len, tydesc);
 }
 
 rust_obstack::~rust_obstack() {
@@ -78,14 +98,14 @@ rust_obstack::~rust_obstack() {
 }
 
 void *
-rust_obstack::alloc(size_t len) {
+rust_obstack::alloc(size_t len, type_desc *tydesc) {
     if (!chunk)
-        return alloc_new(len);
+        return alloc_new(len, tydesc);
 
     DPRINT("alloc sz %u", (uint32_t)len);
 
-    void *ptr = chunk->alloc(len);
-    ptr = ptr ? ptr : alloc_new(len);
+    void *ptr = chunk->alloc(len, tydesc);
+    ptr = ptr ? ptr : alloc_new(len, tydesc);
 
     return ptr;
 }
@@ -107,3 +127,8 @@ rust_obstack::free(void *ptr) {
     }
 }
 
+void *
+rust_obstack::mark() {
+    return chunk ? chunk->mark() : NULL;
+}
+

src/rt/rust_obstack.h

@@ -5,20 +5,22 @@
 
 struct rust_obstack_chunk;
 struct rust_task;
+struct type_desc;
 
 class rust_obstack {
     rust_obstack_chunk *chunk;
     rust_task *task;
 
     // Allocates the given number of bytes in a new chunk.
-    void *alloc_new(size_t len);
+    void *alloc_new(size_t len, type_desc *tydesc);
 
 public:
     rust_obstack(rust_task *in_task) : chunk(NULL), task(in_task) {}
     ~rust_obstack();
 
-    void *alloc(size_t len);
+    void *alloc(size_t len, type_desc *tydesc);
     void free(void *ptr);
+    void *mark();
 };
 
 #endif

src/rt/rust_upcall.cpp

@@ -368,13 +368,26 @@ upcall_vec_push(rust_task* task, rust_vec** vp, type_desc* elt_ty,
  */
 extern "C" CDECL void *
 upcall_dynastack_mark(rust_task *task) {
-    return task->dynastack.alloc(0);
+    return task->dynastack.mark();
 }
 
-/** Allocates space in the dynamic stack and returns it. */
+/**
+ * Allocates space in the dynamic stack and returns it.
+ *
+ * FIXME: Deprecated since dynamic stacks need to be self-describing for GC.
+ */
 extern "C" CDECL void *
 upcall_dynastack_alloc(rust_task *task, size_t sz) {
-    return sz ? task->dynastack.alloc(sz) : NULL;
+    return sz ? task->dynastack.alloc(sz, NULL) : NULL;
+}
+
+/**
+ * Allocates space associated with a type descriptor in the dynamic stack and
+ * returns it.
+ */
+extern "C" CDECL void *
+upcall_dynastack_alloc_2(rust_task *task, size_t sz, type_desc *ty) {
+    return sz ? task->dynastack.alloc(sz, ty) : NULL;
 }
 
 /** Frees space in the dynamic stack. */

src/rt/rustrt.def.in

@@ -77,6 +77,7 @@ task_join
 unsupervise
 upcall_cmp_type
 upcall_dynastack_alloc
+upcall_dynastack_alloc_2
 upcall_dynastack_free
 upcall_dynastack_mark
 upcall_exit