aarch64: Update comments

taiki-e · Jan 7, 2025 · 9d65f58 · 9d65f58
1 parent b6699b4
commit 9d65f58
Showing 1 changed file with 11 additions and 13 deletions.
diff --git a/src/imp/atomic128/aarch64.rs b/src/imp/atomic128/aarch64.rs
@@ -326,8 +326,9 @@ macro_rules! debug_assert_rcpc3 {
 //
 // This is similar to #[target_feature(enable = "lse")], except that there are
 // no compiler guarantees regarding (un)inlining, and the scope is within an asm
-// block rather than a function. We use this directive to support outline-atomics
-// on pre-1.61 rustc (aarch64_target_feature stabilized in Rust 1.61).
+// block rather than a function. We use this directive because #[target_feature(enable = "lse")]
+// is unstable on pre-1.61 rustc and incompatible with rustc_codegen_cranelift:
+// https://github.com/rust-lang/rustc_codegen_cranelift/issues/1400#issuecomment-1774599775
 //
 // The .arch_extension directive is effective until the end of the assembly block and
 // is not propagated to subsequent code, so the end_lse macro is unneeded.
@@ -339,9 +340,6 @@ macro_rules! debug_assert_rcpc3 {
 // The .arch directive has a similar effect, but we don't use it due to the following issue:
 // https://github.com/torvalds/linux/commit/dd1f6308b28edf0452dd5dc7877992903ec61e69
 //
-// This is also needed for compatibility with rustc_codegen_cranelift:
-// https://github.com/rust-lang/rustc_codegen_cranelift/issues/1400#issuecomment-1774599775
-//
 // Note: If FEAT_LSE is not available at compile-time, we must guarantee that
 // the function that uses it is not inlined into a function where it is not
 // clear whether FEAT_LSE is available. Otherwise, (even if we checked whether
@@ -547,7 +545,7 @@ unsafe fn atomic_load(src: *mut u128, order: Ordering) -> u128 {
             atomic_load_no_lse2_seqcst = atomic_load_no_lse2(Ordering::SeqCst);
         }
         // SAFETY: the caller must uphold the safety contract.
-        // and we've checked if FEAT_LSE2 is available.
+        // and we've checked if FEAT_LSE2/FEAT_LRCPC3 is available.
         unsafe {
             match order {
                 Ordering::Relaxed => {
@@ -732,7 +730,7 @@ unsafe fn _atomic_load_ldiapp(src: *mut u128, order: Ordering) -> u128 {
                 // https://github.com/llvm/llvm-project/commit/a6aaa969f7caec58a994142f8d855861cf3a1463
                 #[cfg(portable_atomic_pre_llvm_16)]
                 asm!(
-                    // 0: d9411800     	ldiapp	x0, x1, [x0]
+                    // ldiapp x0, x1, [x0]
                     ".inst 0xd9411800",
                     in("x0") ptr_reg!(src),
                     lateout("x1") out_hi,
@@ -761,7 +759,7 @@ unsafe fn _atomic_load_ldiapp(src: *mut u128, order: Ordering) -> u128 {
                     // ldar (or dmb ishld) is required to prevent reordering with preceding stlxp.
                     // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108891 for details.
                     "ldar {tmp}, [x0]",
-                    // 0: d9411800     	ldiapp	x0, x1, [x0]
+                    // ldiapp x0, x1, [x0]
                     ".inst 0xd9411800",
                     tmp = out(reg) _,
                     in("x0") ptr_reg!(src),
@@ -972,7 +970,7 @@ unsafe fn atomic_store(dst: *mut u128, val: u128, order: Ordering) {
             atomic_store_no_lse2_seqcst = atomic_store_no_lse2(Ordering::SeqCst);
         }
         // SAFETY: the caller must uphold the safety contract.
-        // and we've checked if FEAT_LSE2 is available.
+        // and we've checked if FEAT_LSE2/FEAT_LRCPC3/FEAT_LSE128 is available.
         unsafe {
             match order {
                 Ordering::Relaxed => {
@@ -1173,7 +1171,7 @@ unsafe fn _atomic_store_stilp(dst: *mut u128, val: u128, order: Ordering) {
                 // https://github.com/llvm/llvm-project/commit/a6aaa969f7caec58a994142f8d855861cf3a1463
                 #[cfg(portable_atomic_pre_llvm_16)]
                 asm!(
-                    // 0: d9031802     	stilp	x2, x3, [x0]
+                    // stilp x2, x3, [x0]
                     ".inst 0xd9031802",
                     $acquire,
                     in("x0") ptr_reg!(dst),
@@ -1631,7 +1629,7 @@ unsafe fn _atomic_swap_swpp(dst: *mut u128, val: u128, order: Ordering) -> u128
         macro_rules! swap {
             ($order:tt, $fence:tt) => {
                 asm!(
-                    // 4: 19{2,a,6,e}18002     	swpp{,a,l,al}	x2, x1, [x0]
+                    // swpp{,a,l,al} x2, x1, [x0]
                     concat!(".inst 0x19", $order, "18002"),
                     $fence,
                     in("x0") ptr_reg!(dst),
@@ -2052,7 +2050,7 @@ unsafe fn atomic_and(dst: *mut u128, val: u128, order: Ordering) -> u128 {
         macro_rules! clear {
             ($order:tt, $fence:tt) => {
                 asm!(
-                    // 8: 19{2,a,6,e}11008     	ldclrp{,a,l,al}	x8, x1, [x0]
+                    // ldclrp{,a,l,al} x8, x1, [x0]
                     concat!(".inst 0x19", $order, "11008"),
                     $fence,
                     in("x0") ptr_reg!(dst),
@@ -2130,7 +2128,7 @@ unsafe fn atomic_or(dst: *mut u128, val: u128, order: Ordering) -> u128 {
         macro_rules! or {
             ($order:tt, $fence:tt) => {
                 asm!(
-                    // 4: 19{2,a,6,e}13002     	ldsetp{,a,l,al}	x2, x1, [x0]
+                    // ldsetp{,a,l,al} x2, x1, [x0]
                     concat!(".inst 0x19", $order, "13002"),
                     $fence,
                     in("x0") ptr_reg!(dst),