x86_64: Do not use outline-atomics on target where CPUID is not available

SGX doesn't support CPUID. Currently, on this target, if the cmpxchg16b
feature is not enabled at compile time, detect::has_cmpxchg16b will
always return false.

So, enabling outline-atomics on this target does not make sense since
the fallback implementation is always used.

Author: taiki-e

src/imp/atomic128/detect/x86_64.rs

@@ -2,8 +2,8 @@
 
 #![cfg_attr(
     any(
-        portable_atomic_no_outline_atomics,
         not(target_feature = "sse"),
+        portable_atomic_no_outline_atomics,
         target_env = "sgx",
         miri,
         portable_atomic_sanitize_thread,
@@ -69,7 +69,7 @@ fn _detect(info: &mut CpuInfo) {
     {
         info.set(CpuInfo::HAS_CMPXCHG16B);
     }
-    // sgx doesn't support `cpuid`: https://github.com/rust-lang/stdarch/blob/a0c30f3e3c75adcd6ee7efc94014ebcead61c507/crates/core_arch/src/x86/cpuid.rs#L102-L105
+    // SGX doesn't support CPUID: https://github.com/rust-lang/stdarch/blob/a0c30f3e3c75adcd6ee7efc94014ebcead61c507/crates/core_arch/src/x86/cpuid.rs#L102-L105
     #[cfg(not(any(target_env = "sgx", miri)))]
     {
         use core::arch::x86_64::_xgetbv;
@@ -137,8 +137,8 @@ mod tests {
     }
 
     #[test]
-    // Miri doesn't support inline assembly
-    // sgx doesn't support `cpuid`
+    // SGX doesn't support CPUID.
+    // Miri doesn't support inline assembly.
     #[cfg_attr(any(target_env = "sgx", miri), ignore)]
     fn test_cpuid() {
         assert_eq!(std::is_x86_feature_detected!("cmpxchg16b"), has_cmpxchg16b());

src/imp/atomic128/x86_64.rs

@@ -273,10 +273,12 @@ unsafe fn atomic_load(src: *mut u128, order: Ordering) -> u128 {
 
     // Do not use vector registers on targets such as x86_64-unknown-none unless SSE is explicitly enabled.
     // https://doc.rust-lang.org/nightly/rustc/platform-support/x86_64-unknown-none.html
+    // SGX doesn't support CPUID.
     // Miri and Sanitizer do not support inline assembly.
     #[cfg(any(
-        portable_atomic_no_outline_atomics,
         not(target_feature = "sse"),
+        portable_atomic_no_outline_atomics,
+        target_env = "sgx",
         miri,
         portable_atomic_sanitize_thread,
     ))]
@@ -285,8 +287,9 @@ unsafe fn atomic_load(src: *mut u128, order: Ordering) -> u128 {
         _atomic_load_cmpxchg16b(src, order)
     }
     #[cfg(not(any(
-        portable_atomic_no_outline_atomics,
         not(target_feature = "sse"),
+        portable_atomic_no_outline_atomics,
+        target_env = "sgx",
         miri,
         portable_atomic_sanitize_thread,
     )))]
@@ -316,10 +319,12 @@ unsafe fn atomic_store(dst: *mut u128, val: u128, order: Ordering) {
 
     // Do not use vector registers on targets such as x86_64-unknown-none unless SSE is explicitly enabled.
     // https://doc.rust-lang.org/nightly/rustc/platform-support/x86_64-unknown-none.html
+    // SGX doesn't support CPUID.
     // Miri and Sanitizer do not support inline assembly.
     #[cfg(any(
-        portable_atomic_no_outline_atomics,
         not(target_feature = "sse"),
+        portable_atomic_no_outline_atomics,
+        target_env = "sgx",
         miri,
         portable_atomic_sanitize_thread,
     ))]
@@ -328,8 +333,9 @@ unsafe fn atomic_store(dst: *mut u128, val: u128, order: Ordering) {
         _atomic_store_cmpxchg16b(dst, val, order);
     }
     #[cfg(not(any(
-        portable_atomic_no_outline_atomics,
         not(target_feature = "sse"),
+        portable_atomic_no_outline_atomics,
+        target_env = "sgx",
         miri,
         portable_atomic_sanitize_thread,
     )))]

src/imp/fallback/imp.rs

@@ -3,6 +3,7 @@
         target_arch = "x86_64",
         portable_atomic_cmpxchg16b_target_feature,
         not(portable_atomic_no_outline_atomics),
+        not(target_env = "sgx"),
     ),
     allow(dead_code)
 )]

src/imp/fallback/mod.rs

@@ -86,6 +86,7 @@ pub(crate) use seq_lock::imp::{AtomicI64, AtomicU64};
             target_arch = "x86_64",
             portable_atomic_cmpxchg16b_target_feature,
             not(portable_atomic_no_outline_atomics),
+            not(target_env = "sgx"),
         ),
     ),
     allow(unused_imports)

src/imp/mod.rs

@@ -43,6 +43,7 @@ mod aarch64;
         feature = "fallback",
         portable_atomic_cmpxchg16b_target_feature,
         not(portable_atomic_no_outline_atomics),
+        not(target_env = "sgx"),
     ),
 ))]
 #[cfg(target_arch = "x86_64")]
@@ -323,6 +324,7 @@ pub(crate) use self::aarch64::{AtomicI128, AtomicU128};
             feature = "fallback",
             portable_atomic_cmpxchg16b_target_feature,
             not(portable_atomic_no_outline_atomics),
+            not(target_env = "sgx"),
         ),
     ),
     target_arch = "x86_64",
@@ -353,6 +355,7 @@ pub(crate) use self::s390x::{AtomicI128, AtomicU128};
                 feature = "fallback",
                 portable_atomic_cmpxchg16b_target_feature,
                 not(portable_atomic_no_outline_atomics),
+                not(target_env = "sgx"),
             ),
         ),
         target_arch = "x86_64",

src/lib.rs

@@ -233,6 +233,7 @@ See also [the `atomic128` module's readme](https://github.com/taiki-e/portable-a
         target_arch = "x86_64",
         portable_atomic_unstable_cmpxchg16b_target_feature,
         not(portable_atomic_no_outline_atomics),
+        not(target_env = "sgx"),
         feature = "fallback",
     ),
     feature(cmpxchg16b_target_feature)
@@ -4597,6 +4598,7 @@ atomic_int!(AtomicU64, u64, 8);
                     feature = "fallback",
                     portable_atomic_cmpxchg16b_target_feature,
                     not(portable_atomic_no_outline_atomics),
+                    not(target_env = "sgx"),
                 ),
             ),
             target_arch = "x86_64",
@@ -4649,6 +4651,7 @@ atomic_int!(AtomicI128, i128, 16);
                     feature = "fallback",
                     portable_atomic_cmpxchg16b_target_feature,
                     not(portable_atomic_no_outline_atomics),
+                    not(target_env = "sgx"),
                 ),
             ),
             target_arch = "x86_64",

src/tests/mod.rs

@@ -167,6 +167,7 @@ fn test_is_lock_free() {
                 feature = "fallback",
                 portable_atomic_cmpxchg16b_target_feature,
                 not(portable_atomic_no_outline_atomics),
+                not(target_env = "sgx"),
             )) && std::is_x86_feature_detected!("cmpxchg16b");
             assert_eq!(AtomicI128::is_lock_free(), has_cmpxchg16b);
             assert_eq!(AtomicU128::is_lock_free(), has_cmpxchg16b);

src/utils.rs

@@ -141,6 +141,7 @@ macro_rules! serde_impls {
 // Adapted from https://github.com/BurntSushi/memchr/blob/2.4.1/src/memchr/x86/mod.rs#L9-L71.
 #[allow(unused_macros)]
 #[cfg(not(portable_atomic_no_outline_atomics))]
+#[cfg(any(target_arch = "aarch64", all(target_arch = "x86_64", not(target_env = "sgx"))))]
 macro_rules! ifunc {
     // if the functions are unsafe, this macro is also unsafe.
     (unsafe fn($($arg_pat:ident: $arg_ty:ty),*) $(-> $ret_ty:ty)? { $($if_block:tt)* }) => {{