Add #[cfg(target_has_atomic)] to get atomic support for the current target

Author: Amanieu

src/doc/reference.md

@@ -2091,6 +2091,8 @@ The following configurations must be defined by the implementation:
 * `target_pointer_width = "..."` - Target pointer width in bits. This is set
   to `"32"` for targets with 32-bit pointers, and likewise set to `"64"` for
   64-bit pointers.
+* `target_has_atomic = "..."` - Set of integer sizes on which the target can perform
+  atomic operations. Values are `"8"`, `"16"`, `"32"`, `"64"` and `"ptr"`.
 * `target_vendor = "..."` - Vendor of the target, for example `apple`, `pc`, or
   simply `"unknown"`.
 * `test` - Enabled when compiling the test harness (using the `--test` flag).
@@ -2295,6 +2297,9 @@ The currently implemented features of the reference compiler are:
 * `cfg_target_vendor` - Allows conditional compilation using the `target_vendor`
                         matcher which is subject to change.
 
+* `cfg_target_has_atomic` - Allows conditional compilation using the `target_has_atomic`
+                            matcher which is subject to change.
+
 * `concat_idents` - Allows use of the `concat_idents` macro, which is in many
                     ways insufficient for concatenating identifiers, and may be
                     removed entirely for something more wholesome.

src/libcore/lib.rs

@@ -63,6 +63,7 @@
 #![feature(associated_type_defaults)]
 #![feature(concat_idents)]
 #![feature(const_fn)]
+#![feature(cfg_target_has_atomic)]
 #![feature(custom_attribute)]
 #![feature(fundamental)]
 #![feature(inclusive_range_syntax)]

src/librustc/session/config.rs

@@ -695,6 +695,7 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig {
     let os = &sess.target.target.target_os;
     let env = &sess.target.target.target_env;
     let vendor = &sess.target.target.target_vendor;
+    let max_atomic_width = sess.target.target.options.max_atomic_width;
 
     let fam = if let Some(ref fam) = sess.target.target.options.target_family {
         intern(fam)
@@ -721,6 +722,15 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig {
     if sess.target.target.options.has_elf_tls {
         ret.push(attr::mk_word_item(InternedString::new("target_thread_local")));
     }
+    for &i in &[8, 16, 32, 64, 128] {
+        if i <= max_atomic_width {
+            let s = i.to_string();
+            ret.push(mk(InternedString::new("target_has_atomic"), intern(&s)));
+            if &s == wordsz {
+                ret.push(mk(InternedString::new("target_has_atomic"), intern("ptr")));
+            }
+        }
+    }
     if sess.opts.debug_assertions {
         ret.push(attr::mk_word_item(InternedString::new("debug_assertions")));
     }

src/librustc_back/target/aarch64_apple_ios.rs

@@ -24,6 +24,7 @@ pub fn target() -> Target {
         options: TargetOptions {
             features: "+neon,+fp-armv8,+cyclone".to_string(),
             eliminate_frame_pointer: false,
+            max_atomic_width: 128,
             .. opts(Arch::Arm64)
         },
     }

src/librustc_back/target/aarch64_linux_android.rs

@@ -11,6 +11,8 @@
 use target::Target;
 
 pub fn target() -> Target {
+    let mut base = super::android_base::opts();
+    base.max_atomic_width = 128;
     Target {
         llvm_target: "aarch64-linux-android".to_string(),
         target_endian: "little".to_string(),
@@ -20,6 +22,6 @@ pub fn target() -> Target {
         target_os: "android".to_string(),
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
-        options: super::android_base::opts(),
+        options: base,
     }
 }

src/librustc_back/target/aarch64_unknown_linux_gnu.rs

@@ -11,7 +11,8 @@
 use target::Target;
 
 pub fn target() -> Target {
-    let base = super::linux_base::opts();
+    let mut base = super::linux_base::opts();
+    base.max_atomic_width = 128;
     Target {
         llvm_target: "aarch64-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),

src/librustc_back/target/arm_linux_androideabi.rs

@@ -13,6 +13,7 @@ use target::Target;
 pub fn target() -> Target {
     let mut base = super::android_base::opts();
     base.features = "+v7,+vfp3,+d16".to_string();
+    base.max_atomic_width = 64;
 
     Target {
         llvm_target: "arm-linux-androideabi".to_string(),

src/librustc_back/target/arm_unknown_linux_gnueabi.rs

@@ -11,7 +11,8 @@
 use target::{Target, TargetOptions};
 
 pub fn target() -> Target {
-    let base = super::linux_base::opts();
+    let mut base = super::linux_base::opts();
+    base.max_atomic_width = 64;
     Target {
         llvm_target: "arm-unknown-linux-gnueabi".to_string(),
         target_endian: "little".to_string(),

src/librustc_back/target/arm_unknown_linux_gnueabihf.rs

@@ -11,7 +11,8 @@
 use target::{Target, TargetOptions};
 
 pub fn target() -> Target {
-    let base = super::linux_base::opts();
+    let mut base = super::linux_base::opts();
+    base.max_atomic_width = 64;
     Target {
         llvm_target: "arm-unknown-linux-gnueabihf".to_string(),
         target_endian: "little".to_string(),

src/librustc_back/target/armv7_apple_ios.rs

@@ -23,6 +23,7 @@ pub fn target() -> Target {
         target_vendor: "apple".to_string(),
         options: TargetOptions {
             features: "+v7,+vfp3,+neon".to_string(),
+            max_atomic_width: 64,
             .. opts(Arch::Armv7)
         }
     }