std: Re-optimize tls access on local allocation path

I did this once but acciddentally undid it in a later patch.

src/libstd/rt/local.rs

@@ -45,11 +45,7 @@ impl Local for Task {
     }
     unsafe fn unsafe_borrow() -> *mut Task { local_ptr::unsafe_borrow() }
     unsafe fn try_unsafe_borrow() -> Option<*mut Task> {
-        if Local::exists::<Task>() {
-            Some(Local::unsafe_borrow())
-        } else {
-            None
-        }
+        local_ptr::try_unsafe_borrow()
     }
 }
 

src/libstd/rt/local_heap.rs

@@ -13,6 +13,7 @@
 use libc;
 use libc::{c_void, uintptr_t, size_t};
 use ops::Drop;
+use option::{Some, None};
 use rt::local::Local;
 use rt::task::Task;
 use unstable::raw;
@@ -84,8 +85,12 @@ impl Drop for LocalHeap {
 
 // A little compatibility function
 pub unsafe fn local_free(ptr: *libc::c_char) {
-    do Local::borrow::<Task,()> |task| {
-        task.heap.free(ptr as *libc::c_void);
+    // XXX: Unsafe borrow for speed. Lame.
+    match Local::try_unsafe_borrow::<Task>() {
+        Some(task) => {
+            (*task).heap.free(ptr as *libc::c_void);
+        }
+        None => rtabort!("local free outside of task")
     }
 }
 

src/libstd/rt/local_ptr.rs

@@ -97,16 +97,23 @@ pub unsafe fn borrow<T>(f: &fn(&mut T)) {
 /// Because this leaves the value in thread-local storage it is possible
 /// For the Scheduler pointer to be aliased
 pub unsafe fn unsafe_borrow<T>() -> *mut T {
+    match try_unsafe_borrow() {
+        Some(p) => p,
+        None => rtabort!("thread-local pointer is null. bogus!")
+    }
+}
+
+pub unsafe fn try_unsafe_borrow<T>() -> Option<*mut T> {
     let key = tls_key();
     let mut void_ptr: *mut c_void = tls::get(key);
     if void_ptr.is_null() {
-        rtabort!("thread-local pointer is null. bogus!");
+        return None;
     }
     {
         let ptr: *mut *mut c_void = &mut void_ptr;
         let ptr: *mut ~T = ptr as *mut ~T;
         let ptr: *mut T = &mut **ptr;
-        return ptr;
+        return Some(ptr);
     }
 }
 

src/libstd/unstable/lang.rs

@@ -13,6 +13,7 @@
 use c_str::ToCStr;
 use cast::transmute;
 use libc::{c_char, c_void, size_t, uintptr_t};
+use option::{Some, None};
 use sys;
 use rt::task::Task;
 use rt::local::Local;
@@ -35,14 +36,13 @@ pub fn fail_bounds_check(file: *c_char, line: size_t,
 
 #[lang="malloc"]
 pub unsafe fn local_malloc(td: *c_char, size: uintptr_t) -> *c_char {
-    let mut alloc = ::ptr::null();
-    do Local::borrow::<Task,()> |task| {
-        rtdebug!("task pointer: %x, heap pointer: %x",
-                 ::borrow::to_uint(task),
-                 ::borrow::to_uint(&task.heap));
-        alloc = task.heap.alloc(td as *c_void, size as uint) as *c_char;
+    // XXX: Unsafe borrow for speed. Lame.
+    match Local::try_unsafe_borrow::<Task>() {
+        Some(task) => {
+            (*task).heap.alloc(td as *c_void, size as uint) as *c_char
+        }
+        None => rtabort!("local malloc outside of task")
     }
-    return alloc;
 }
 
 // NB: Calls to free CANNOT be allowed to fail, as throwing an exception from