From d8c5bd61956924e041be240cff9458141ca74187 Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Tue, 16 Aug 2011 19:48:47 -0700
Subject: [PATCH] rt: Implement obstacks, untested as of yet

---
 mk/rt.mk                |  1 +
 src/rt/rust_obstack.cpp | 82 +++++++++++++++++++++++++++++++++++++++++
 src/rt/rust_obstack.h   | 24 ++++++++++++
 src/rt/rust_task.cpp    |  3 +-
 src/rt/rust_task.h      |  3 ++
 src/rt/rust_upcall.cpp  | 22 +++++++++++
 src/rt/rustrt.def.in    |  3 ++
 7 files changed, 137 insertions(+), 1 deletion(-)
 create mode 100644 src/rt/rust_obstack.cpp
 create mode 100644 src/rt/rust_obstack.h

diff --git a/mk/rt.mk b/mk/rt.mk
index 11e110666ab..6082baf01c9 100644
--- a/mk/rt.mk
+++ b/mk/rt.mk
@@ -25,6 +25,7 @@ RUNTIME_CS := rt/sync/timer.cpp \
               rt/rust_srv.cpp \
               rt/rust_kernel.cpp \
               rt/rust_shape.cpp \
+              rt/rust_obstack.cpp \
               rt/memory_region.cpp \
               rt/test/rust_test_harness.cpp \
               rt/test/rust_test_runtime.cpp \
diff --git a/src/rt/rust_obstack.cpp b/src/rt/rust_obstack.cpp
new file mode 100644
index 00000000000..342310d4b5c
--- /dev/null
+++ b/src/rt/rust_obstack.cpp
@@ -0,0 +1,82 @@
+// Object stacks, used in lieu of dynamically-sized frames.
+
+#include <algorithm>
+#include <cassert>
+#include <cstdlib>
+#include <stdint.h>
+
+#include "rust_internal.h"
+#include "rust_obstack.h"
+#include "rust_task.h"
+
+// ISAAC, let go of max()!
+#ifdef max
+#undef max
+#endif
+
+const size_t DEFAULT_CHUNK_SIZE = 4096;
+
+struct rust_obstack_chunk {
+    rust_obstack_chunk *prev;
+    size_t size;
+    size_t alen;
+    size_t pad;
+    uint8_t data[];
+
+    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);
+    bool free(void *ptr);
+};
+
+void *
+rust_obstack_chunk::alloc(size_t len) {
+    if (len > size - alen)
+        return NULL;    // Not enough space.
+    void *result = data + alen;
+    alen += len;
+    return result;
+}
+
+bool
+rust_obstack_chunk::free(void *ptr) {
+    uint8_t *p = (uint8_t *)ptr;
+    if (p < data || p >= data + size)
+        return false;
+    assert(p < data + alen);
+    alen = (size_t)(p - data);
+    return true;
+}
+
+// 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);
+    void *ptr = task->malloc(sizeof(chunk) + chunk_size, "obstack");
+    chunk = new(ptr) rust_obstack_chunk(chunk, chunk_size);
+    return chunk->alloc(len);
+}
+
+void *
+rust_obstack::alloc(size_t len) {
+    if (!chunk)
+        return alloc_new(len);
+    void *ptr = chunk->alloc(len);
+    return ptr ? ptr : alloc_new(len);
+}
+
+void
+rust_obstack::free(void *ptr) {
+    if (!ptr)
+        return;
+
+    assert(chunk);
+    while (!chunk->free(ptr)) {
+        rust_obstack_chunk *prev = chunk->prev;
+        task->free(chunk);
+        chunk = prev;
+        assert(chunk);
+    }
+}
+
diff --git a/src/rt/rust_obstack.h b/src/rt/rust_obstack.h
new file mode 100644
index 00000000000..5a80638aba7
--- /dev/null
+++ b/src/rt/rust_obstack.h
@@ -0,0 +1,24 @@
+// Object stacks, used in lieu of dynamically-sized frames.
+
+#ifndef RUST_OBSTACK_H
+#define RUST_OBSTACK_H
+
+struct rust_obstack_chunk;
+struct rust_task;
+
+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);
+
+public:
+    rust_obstack(rust_task *in_task) : chunk(NULL), task(in_task) {}
+
+    void *alloc(size_t len);
+    void free(void *ptr);
+};
+
+#endif
+
diff --git a/src/rt/rust_task.cpp b/src/rt/rust_task.cpp
index c877d5e9941..b8269554237 100644
--- a/src/rt/rust_task.cpp
+++ b/src/rt/rust_task.cpp
@@ -75,7 +75,8 @@ rust_task::rust_task(rust_scheduler *sched, rust_task_list *state,
     local_region(&sched->srv->local_region),
     _on_wakeup(NULL),
     failed(false),
-    propagate_failure(true)
+    propagate_failure(true),
+    dynastack(this)
 {
     LOGPTR(sched, "new task", (uintptr_t)this);
     DLOG(sched, task, "sizeof(task) = %d (0x%x)", sizeof *this, sizeof *this);
diff --git a/src/rt/rust_task.h b/src/rt/rust_task.h
index a688c405e60..f1513ada616 100644
--- a/src/rt/rust_task.h
+++ b/src/rt/rust_task.h
@@ -8,6 +8,7 @@
 #include "util/array_list.h"
 
 #include "context.h"
+#include "rust_obstack.h"
 
 struct stk_seg {
     unsigned int valgrind_id;
@@ -122,6 +123,8 @@ rust_task : public kernel_owned<rust_task>, rust_cond
 
     hash_map<rust_port_id, rust_port *> port_table;
 
+    rust_obstack dynastack;
+
     // Only a pointer to 'name' is kept, so it must live as long as this task.
     rust_task(rust_scheduler *sched,
               rust_task_list *state,
diff --git a/src/rt/rust_upcall.cpp b/src/rt/rust_upcall.cpp
index 5fd0127c7e7..d04de59a4df 100644
--- a/src/rt/rust_upcall.cpp
+++ b/src/rt/rust_upcall.cpp
@@ -417,6 +417,28 @@ upcall_ivec_spill_shared(rust_task *task,
     v->alloc = new_alloc;
     v->payload.ptr = heap_part;
 }
+
+/**
+ * Returns a token that can be used to deallocate all of the allocated space
+ * space in the dynamic stack.
+ */
+extern "C" CDECL void *
+upcall_dynastack_mark(rust_task *task) {
+    return task->dynastack.alloc(0);
+}
+
+/** Allocates space in the dynamic stack and returns it. */
+extern "C" CDECL void *
+upcall_dynastack_alloc(rust_task *task, size_t sz) {
+    return task->dynastack.alloc(sz);
+}
+
+/** Frees space in the dynamic stack. */
+extern "C" CDECL void
+upcall_dynastack_free(rust_task *task, void *ptr) {
+    return task->dynastack.free(ptr);
+}
+
 //
 // Local Variables:
 // mode: C++
diff --git a/src/rt/rustrt.def.in b/src/rt/rustrt.def.in
index c200fc9d3cb..0d05d7ffa43 100644
--- a/src/rt/rustrt.def.in
+++ b/src/rt/rustrt.def.in
@@ -83,6 +83,9 @@ task_yield
 task_join
 unsupervise
 upcall_cmp_type
+upcall_dynastack_alloc
+upcall_dynastack_free
+upcall_dynastack_mark
 upcall_exit
 upcall_fail
 upcall_free