From 1795ae4e8a472ce500660fa59abf61114f5ef8c9 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Wed, 6 Nov 2013 00:38:08 -0500
Subject: [PATCH] add `#[thread_local]` attribute

This provides a building block for fast thread-local storage. It does
not change the safety semantics of `static mut`.

Closes #10310
---
 doc/rust.md                       | 2 ++
 src/librustc/lib/llvm.rs          | 6 ++++++
 src/librustc/middle/lint.rs       | 1 +
 src/librustc/middle/trans/base.rs | 4 ++++
 4 files changed, 13 insertions(+)

diff --git a/doc/rust.md b/doc/rust.md
index fe8d0a834e3..f15e767ca82 100644
--- a/doc/rust.md
+++ b/doc/rust.md
@@ -1754,6 +1754,8 @@ names are effectively reserved. Some significant attributes include:
 * The `deriving` attribute, for automatically generating
   implementations of certain traits.
 * The `static_assert` attribute, for asserting that a static bool is true at compiletime
+* The `thread_local` attribute, for defining a `static mut` as a thread-local. Note that this is
+  only a low-level building block, and is not local to a *task*, nor does it provide safety.
 
 Other attributes may be added or removed during development of the language.
 
diff --git a/src/librustc/lib/llvm.rs b/src/librustc/lib/llvm.rs
index 160bc511168..66f6e6a4746 100644
--- a/src/librustc/lib/llvm.rs
+++ b/src/librustc/lib/llvm.rs
@@ -1749,6 +1749,12 @@ pub fn SetUnnamedAddr(Global: ValueRef, Unnamed: bool) {
     }
 }
 
+pub fn set_thread_local(global: ValueRef, is_thread_local: bool) {
+    unsafe {
+        llvm::LLVMSetThreadLocal(global, is_thread_local as Bool);
+    }
+}
+
 pub fn ConstICmp(Pred: IntPredicate, V1: ValueRef, V2: ValueRef) -> ValueRef {
     unsafe {
         llvm::LLVMConstICmp(Pred as c_ushort, V1, V2)
diff --git a/src/librustc/middle/lint.rs b/src/librustc/middle/lint.rs
index 2b2c2aa74c7..a08afcfd7c5 100644
--- a/src/librustc/middle/lint.rs
+++ b/src/librustc/middle/lint.rs
@@ -816,6 +816,7 @@ fn check_heap_item(cx: &Context, it: &ast::item) {
 static other_attrs: &'static [&'static str] = &[
     // item-level
     "address_insignificant", // can be crate-level too
+    "thread_local", // for statics
     "allow", "deny", "forbid", "warn", // lint options
     "deprecated", "experimental", "unstable", "stable", "locked", "frozen", //item stability
     "crate_map", "cfg", "doc", "export_name", "link_section", "no_freeze",
diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index 0ece7c8c024..20cc2f8944e 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -2543,6 +2543,10 @@ pub fn get_item_val(ccx: @mut CrateContext, id: ast::NodeId) -> ValueRef {
                                     inlineable = true;
                                 }
 
+                                if attr::contains_name(i.attrs, "thread_local") {
+                                    lib::llvm::set_thread_local(g, true);
+                                }
+
                                 if !inlineable {
                                     debug!("{} not inlined", sym);
                                     ccx.non_inlineable_statics.insert(id);
-- 
2.44.0