Revert "Use asm-based atomic load/store on thumbv6m"

This reverts commit a864da7.

rust-lang/rust#99595 has been reverted, so this
is no longer needed.

Author: taiki-e

README.md

@@ -13,7 +13,7 @@ Portable atomic types including support for 128-bit atomics, atomic float, etc.
 - Provide `AtomicI128` and `AtomicU128`.
 - Provide `AtomicF32` and `AtomicF64`. (optional)
 <!-- - Provide generic `Atomic<T>` type. (optional) -->
-- Provide atomic load/store for targets where atomic is not available at all in the standard library. (thumbv6m, riscv without A-extension, msp430, avr)
+- Provide atomic load/store for targets where atomic is not available at all in the standard library. (riscv without A-extension, msp430, avr)
 - Provide atomic CAS for targets where atomic CAS is not available in the standard library. (thumbv6m, riscv without A-extension, msp430, avr) (optional, [single-core only](#optional-cfg))
 - Make features that require newer compilers, such as [fetch_max](https://doc.rust-lang.org/std/sync/atomic/struct.AtomicUsize.html#method.fetch_max), [fetch_min](https://doc.rust-lang.org/std/sync/atomic/struct.AtomicUsize.html#method.fetch_min), [fetch_update](https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicPtr.html#method.fetch_update), and [stronger CAS failure ordering](https://github.com/rust-lang/rust/pull/98383) available on Rust 1.34+.
 

no_atomic.rs

@@ -69,5 +69,4 @@ const NO_ATOMIC: &[&str] = &[
     "riscv32i-unknown-none-elf",
     "riscv32im-unknown-none-elf",
     "riscv32imc-unknown-none-elf",
-    "thumbv6m-none-eabi",
 ];

src/imp/arm.rs

@@ -16,12 +16,12 @@
 // CAS together with atomic load/store. The load/store will not be
 // called while interrupts are disabled, and since the load/store is
 // atomic, it is not affected by interrupts even if interrupts are enabled.
-#[cfg(portable_atomic_armv6m)]
-use super::arm as atomic;
 #[cfg(target_arch = "msp430")]
 use super::msp430 as atomic;
 #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
 use super::riscv as atomic;
+#[cfg(target_arch = "arm")]
+use core::sync::atomic;
 
 #[cfg_attr(portable_atomic_armv6m, path = "armv6m.rs")]
 #[cfg_attr(target_arch = "avr", path = "avr.rs")]

src/imp/interrupt/mod.rs

@@ -39,14 +39,6 @@ mod s390x;
 #[cfg(target_arch = "msp430")]
 mod msp430;
 
-#[cfg(any(not(portable_atomic_no_asm), portable_atomic_nightly))]
-#[cfg(portable_atomic_armv6m)]
-mod arm;
-#[cfg(not(any(not(portable_atomic_no_asm), portable_atomic_nightly)))]
-#[cfg(portable_atomic_armv6m)]
-#[path = "core_atomic.rs"]
-mod arm;
-
 #[cfg_attr(portable_atomic_no_cfg_target_has_atomic, cfg(any(test, portable_atomic_no_atomic_cas)))]
 #[cfg_attr(
     not(portable_atomic_no_cfg_target_has_atomic),
@@ -132,12 +124,6 @@ mod interrupt;
 pub(crate) use self::core_atomic::{
     AtomicBool, AtomicI16, AtomicI8, AtomicIsize, AtomicPtr, AtomicU16, AtomicU8, AtomicUsize,
 };
-// armv6m
-#[cfg(not(portable_atomic_unsafe_assume_single_core))]
-#[cfg(portable_atomic_armv6m)]
-pub(crate) use self::arm::{
-    AtomicBool, AtomicI16, AtomicI8, AtomicIsize, AtomicPtr, AtomicU16, AtomicU8, AtomicUsize,
-};
 // msp430
 #[cfg(not(portable_atomic_unsafe_assume_single_core))]
 #[cfg(target_arch = "msp430")]
@@ -189,10 +175,6 @@ pub(crate) use self::interrupt::{
     ))
 )]
 pub(crate) use self::core_atomic::{AtomicI32, AtomicU32};
-// armv6m
-#[cfg(not(portable_atomic_unsafe_assume_single_core))]
-#[cfg(portable_atomic_armv6m)]
-pub(crate) use self::arm::{AtomicI32, AtomicU32};
 // riscv32 without A-extension
 #[cfg(not(portable_atomic_unsafe_assume_single_core))]
 #[cfg(target_arch = "riscv32")]

src/imp/mod.rs

@@ -5,7 +5,7 @@ Portable atomic types including support for 128-bit atomics, atomic float, etc.
 - Provide `AtomicI128` and `AtomicU128`.
 - Provide `AtomicF32` and `AtomicF64`. (optional)
 <!-- - Provide generic `Atomic<T>` type. (optional) -->
-- Provide atomic load/store for targets where atomic is not available at all in the standard library. (thumbv6m, riscv without A-extension, msp430, avr)
+- Provide atomic load/store for targets where atomic is not available at all in the standard library. (riscv without A-extension, msp430, avr)
 - Provide atomic CAS for targets where atomic CAS is not available in the standard library. (thumbv6m, riscv without A-extension, msp430, avr) (optional, [single-core only](#optional-cfg))
 - Make features that require newer compilers, such as [fetch_max](https://doc.rust-lang.org/std/sync/atomic/struct.AtomicUsize.html#method.fetch_max), [fetch_min](https://doc.rust-lang.org/std/sync/atomic/struct.AtomicUsize.html#method.fetch_min), [fetch_update](https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicPtr.html#method.fetch_update), and [stronger CAS failure ordering](https://github.com/rust-lang/rust/pull/98383) available on Rust 1.34+.
 

src/lib.rs

@@ -13,9 +13,7 @@ file="no_atomic.rs"
 
 no_atomic_cas=()
 no_atomic_64=()
-no_atomic=(
-    "thumbv6m-none-eabi" # https://github.com/rust-lang/rust/pull/99595
-)
+no_atomic=()
 for target in $(rustc --print target-list); do
     target_spec=$(rustc --print target-spec-json -Z unstable-options --target "${target}")
     res=$(jq <<<"${target_spec}" -r 'select(."atomic-cas" == false)')