Various cleanup

- Optimize x86_64 128-bit outline-atomics. FYI, this improves performance by up to 15% in concurrent RMW/store microbenchmarks. - Optimize x86_64 128-bit load that uses cmpxchg16b. - Optimize aarch64 128-bit load that uses FEAT_LSE. - Move 128-bit atomic implementation for Miri and ThreadSanitizer to intrinsics.rs on all architectures. - Remove duplicate tests and add tests for cases where feature detection returns false. - Several minor cleanups.
taiki-e · Apr 18, 2023 · 40c4cd4 · 40c4cd4
1 parent 0a7d5d2
commit 40c4cd4
Show file tree

Hide file tree

Showing 28 changed files with 1,049 additions and 1,298 deletions.
diff --git a/.cirrus.yml b/.cirrus.yml
@@ -36,11 +36,11 @@ aarch64_linux_gnu_test_task:
     - |
       [ ! -f $HOME/.cargo/env ] || . $HOME/.cargo/env
     - set -ex
-    - ./tools/test.sh -vv
+    - ./tools/test.sh -vv -- -Z unstable-options --report-time
     # +lse
     # Graviton2 (Neoverse N1) is ARMv8.2-a and doesn't support FEAT_LSE2.
     # FEAT_LSE2 is tested on aarch64 macOS VM.
-    - RUSTFLAGS="$RUSTFLAGS -C target-feature=+lse" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=+lse" ./tools/test.sh -vv
+    - RUSTFLAGS="$RUSTFLAGS -C target-feature=+lse" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=+lse" ./tools/test.sh -vv -- -Z unstable-options --report-time
 
 aarch64_linux_musl_test_task:
   name: test ($TARGET)
@@ -55,47 +55,36 @@ aarch64_linux_musl_test_task:
     - rustup toolchain add nightly --no-self-update --component rust-src && rustup default nightly
   test_script:
     - set -ex
-    - ./tools/test.sh -vv
+    - ./tools/test.sh -vv -- -Z unstable-options --report-time
     # -crt-static
-    - RUSTFLAGS="$RUSTFLAGS -C target-feature=-crt-static" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=-crt-static" ./tools/test.sh -vv
+    - RUSTFLAGS="$RUSTFLAGS -C target-feature=-crt-static" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=-crt-static" ./tools/test.sh -vv -- -Z unstable-options --report-time
     # +lse
     # Graviton2 (Neoverse N1) is ARMv8.2-a and doesn't support FEAT_LSE2.
     # FEAT_LSE2 is tested on aarch64 macOS VM.
-    - RUSTFLAGS="$RUSTFLAGS -C target-feature=+lse" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=+lse" ./tools/test.sh -vv
+    - RUSTFLAGS="$RUSTFLAGS -C target-feature=+lse" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=+lse" ./tools/test.sh -vv -- -Z unstable-options --report-time
 
-armel_linux_test_task:
+arm_linux_test_task:
   name: test ($TARGET)
-  env:
-    TARGET: armv5te-unknown-linux-gnueabi
+  matrix:
+    - env:
+        TARGET: armv5te-unknown-linux-gnueabi
+        DPKG_ARCH: armel
+    - env:
+        TARGET: armv7-unknown-linux-gnueabihf
+        DPKG_ARCH: armhf
   arm_container:
     image: rust:latest
   setup_script:
     - set -ex
     - lscpu
     - rustup toolchain add nightly --no-self-update --component rust-src && rustup default nightly
-    - dpkg --add-architecture armel
-    - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends gcc-arm-linux-gnueabi libc6-dev-armel-cross libc6:armel
+    - dpkg --add-architecture "$DPKG_ARCH"
+    - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends gcc-"${TARGET/*-unknown/arm}" libc6-dev-"$DPKG_ARCH"-cross libc6:"$DPKG_ARCH"
   test_script:
     - set -ex
     - export CARGO_TARGET_ARMV5TE_UNKNOWN_LINUX_GNUEABI_LINKER=arm-linux-gnueabi-gcc
-    - ./tools/test.sh --target "$TARGET" -Z doctest-xcompile -vv
-
-armhf_linux_test_task:
-  name: test ($TARGET)
-  env:
-    TARGET: armv7-unknown-linux-gnueabihf
-  arm_container:
-    image: rust:latest
-  setup_script:
-    - set -ex
-    - lscpu
-    - rustup toolchain add nightly --no-self-update --component rust-src && rustup default nightly
-    - dpkg --add-architecture armhf
-    - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends gcc-arm-linux-gnueabihf libc6-dev-armhf-cross libc6:armhf
-  test_script:
-    - set -ex
     - export CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_LINKER=arm-linux-gnueabihf-gcc
-    - ./tools/test.sh --target "$TARGET" -Z doctest-xcompile -vv
+    - ./tools/test.sh --target "$TARGET" -Z doctest-xcompile -vv -- -Z unstable-options --report-time
 
 aarch64_macos_test_task:
   name: test ($TARGET)
@@ -111,32 +100,28 @@ aarch64_macos_test_task:
     - . $HOME/.cargo/env
     - set -ex
     # macOS is +lse,+lse2 by default
-    - ./tools/test.sh -vv
+    - ./tools/test.sh -vv -- -Z unstable-options --report-time
 
 aarch64_linux_valgrind_task:
   name: valgrind ($TARGET)
   env:
-    CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_RUNNER: valgrind -v --error-exitcode=1 --error-limit=no --leak-check=full --show-leak-kinds=all --track-origins=yes
-    RUSTDOCFLAGS: -D warnings --cfg valgrind
-    RUSTFLAGS: -D warnings --cfg valgrind
+    VALGRIND: valgrind
     TARGET: aarch64-unknown-linux-gnu
   arm_container:
     # Valgrind support ldxp/stxp on 3.19+: https://valgrind.org/docs/manual/dist.news.html
     # However, current Debian stable's Valgrind is 3.16: https://packages.debian.org/en/stable/valgrind
     image: debian:bookworm
   setup_script:
     - set -ex
-    - lscpu
-    - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends ca-certificates curl gcc git libc6-dev valgrind
+    - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends ca-certificates curl gcc git libc6-dev valgrind moreutils
     - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal --default-toolchain nightly --component rust-src
   test_script:
     - . $HOME/.cargo/env
     - set -ex
-    # doctests on Valgrind are very slow
-    - ./tools/test.sh -vv --tests
+    - ./tools/test.sh -vv 2>&1 | ts -i '%.s  '
     # +lse
     # As of Valgrind 3.19, Valgrind supports atomic instructions of ARMv8.0 and ARMv8.1 (FEAT_LSE).
-    - RUSTFLAGS="$RUSTFLAGS -C target-feature=+lse" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=+lse" ./tools/test.sh -vv --tests
+    - RUSTFLAGS="$RUSTFLAGS -C target-feature=+lse" RUSTDOCFLAGS="$RUSTDOCFLAGS -C target-feature=+lse" ./tools/test.sh -vv 2>&1 | ts -i '%.s  '
 #
 # aarch64_linux_bench_task:
 #   name: bench ($TARGET)
@@ -152,33 +137,36 @@ aarch64_linux_valgrind_task:
 #     - rustup toolchain add nightly --no-self-update && rustup default nightly
 #   bench_script:
 #     - set -ex
+#     - cargo bench -vv --manifest-path bench/Cargo.toml
 #     - RUSTFLAGS="${RUSTFLAGS} -C target-feature=-outline-atomics --cfg portable_atomic_no_outline_atomics" cargo bench -vv --manifest-path bench/Cargo.toml
 #     - RUSTFLAGS="${RUSTFLAGS} -C target-feature=+lse" cargo bench -vv --manifest-path bench/Cargo.toml
 
-# armel_linux_bench_task:
+# x86_64_linux_bench_task:
 #   name: bench ($TARGET)
 #   env:
-#     TARGET: armv5te-unknown-linux-gnueabi
-#   arm_container:
+#     TARGET: x86_64-unknown-linux-gnu
+#   container:
 #     image: rust:latest
 #     cpu: 4
 #     memory: 12G
 #   setup_script:
 #     - set -ex
 #     - lscpu
-#     - rustup toolchain add nightly --no-self-update --component rust-src && rustup default nightly
-#     - rustup target add "$TARGET"
-#     - dpkg --add-architecture armel
-#     - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends gcc-arm-linux-gnueabi libc6-dev-armel-cross libc6:armel
-#   test_script:
+#     - rustup toolchain add nightly --no-self-update && rustup default nightly
+#   bench_script:
 #     - set -ex
-#     - export CARGO_TARGET_ARMV5TE_UNKNOWN_LINUX_GNUEABI_LINKER=arm-linux-gnueabi-gcc
-#     - RUSTFLAGS="${RUSTFLAGS}" cargo bench --target "$TARGET" -vv --manifest-path bench/Cargo.toml
+#     - cargo bench -vv --manifest-path bench/Cargo.toml
+#     - RUSTFLAGS="${RUSTFLAGS} -C target-feature=+cmpxchg16b" cargo bench -vv --manifest-path bench/Cargo.toml
 
-# armhf_linux_bench_task:
+# arm_linux_bench_task:
 #   name: bench ($TARGET)
-#   env:
-#     TARGET: armv7-unknown-linux-gnueabihf
+#   matrix:
+#     - env:
+#         TARGET: armv5te-unknown-linux-gnueabi
+#         DPKG_ARCH: armel
+#     - env:
+#         TARGET: armv7-unknown-linux-gnueabihf
+#         DPKG_ARCH: armhf
 #   arm_container:
 #     image: rust:latest
 #     cpu: 4
@@ -188,10 +176,11 @@ aarch64_linux_valgrind_task:
 #     - lscpu
 #     - rustup toolchain add nightly --no-self-update --component rust-src && rustup default nightly
 #     - rustup target add "$TARGET"
-#     - dpkg --add-architecture armhf
-#     - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends gcc-arm-linux-gnueabihf libc6-dev-armhf-cross libc6:armhf
+#     - dpkg --add-architecture "$DPKG_ARCH"
+#     - apt-get -o Acquire::Retries=10 -qq update && apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends gcc-"${TARGET/*-unknown/arm}" libc6-dev-"$DPKG_ARCH"-cross libc6:"$DPKG_ARCH"
 #   test_script:
 #     - set -ex
+#     - export CARGO_TARGET_ARMV5TE_UNKNOWN_LINUX_GNUEABI_LINKER=arm-linux-gnueabi-gcc
 #     - export CARGO_TARGET_ARMV7_UNKNOWN_LINUX_GNUEABIHF_LINKER=arm-linux-gnueabihf-gcc
 #     - RUSTFLAGS="${RUSTFLAGS}" cargo bench --target "$TARGET" -vv --manifest-path bench/Cargo.toml
 

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -95,8 +95,6 @@ jobs:
             target: armv7-unknown-linux-gnueabi
           - rust: nightly
             target: armv7-unknown-linux-gnueabihf
-          - rust: nightly
-            target: armv5te-unknown-linux-musleabi
           - rust: nightly
             target: arm-linux-androideabi
           - rust: nightly
@@ -163,42 +161,53 @@ jobs:
         if: matrix.target != '' && !startsWith(matrix.target, 'i686') && !startsWith(matrix.target, 'x86_64')
       - run: echo "TARGET=--target=${{ matrix.target }}" >>"${GITHUB_ENV}"
         if: matrix.target != ''
+      - run: echo "REPORT_TIME=-- -Z unstable-options --report-time" >>"${GITHUB_ENV}"
+        if: startsWith(matrix.rust, 'nightly')
         # Since nightly-2022-12-23, -Z build-std + -Z randomize-layout + release mode on windows causes segfault.
       - run: echo "RANDOMIZE_LAYOUT=-Z randomize-layout" >>"${GITHUB_ENV}"
         if: startsWith(matrix.rust, 'nightly') && !startsWith(matrix.os, 'windows')
 
-      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD
+      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD $REPORT_TIME
+      # macOS is skipped because it is +cmpxchg16b by default
+      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD $REPORT_TIME
+        env:
+          # Note: This cfg is intended to make it easy for portable-atomic developers
+          # to test has_cmpxchg16b == false, has_lse == false, or __kuser_helper_version < 5 cases,
+          # and is not a public API.
+          RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} --cfg portable_atomic_test_outline_atomics_detect_false
+          RUSTFLAGS: ${{ env.RUSTFLAGS }} --cfg portable_atomic_test_outline_atomics_detect_false
+        if: (matrix.target == '' || startsWith(matrix.target, 'x86_64')) && !startsWith(matrix.os, 'macos') || startsWith(matrix.target, 'aarch64') || startsWith(matrix.target, 'armv5te') || matrix.target == 'arm-linux-androideabi'
       # -crt-static
-      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD
+      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD $REPORT_TIME
         env:
           RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -C target-feature=-crt-static
           RUSTFLAGS: ${{ env.RUSTFLAGS }} -C target-feature=-crt-static
         if: contains(matrix.target, '-musl')
       # +cmpxchg16b
       # macOS is skipped because it is +cmpxchg16b by default
-      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD
+      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD $REPORT_TIME
         env:
           RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -C target-feature=+cmpxchg16b
           RUSTFLAGS: ${{ env.RUSTFLAGS }} -C target-feature=+cmpxchg16b
         if: (matrix.target == '' || startsWith(matrix.target, 'x86_64')) && !startsWith(matrix.os, 'macos')
       # +lse
       # As of QEMU 7.2, QEMU has not yet implemented FEAT_LSE2: https://linaro.atlassian.net/browse/QEMU-300
       # FEAT_LSE2 is tested on Cirrus CI's aarch64 macOS VM.
-      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD
+      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD $REPORT_TIME
         env:
           RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -C target-feature=+lse
           RUSTFLAGS: ${{ env.RUSTFLAGS }} -C target-feature=+lse
         if: startsWith(matrix.target, 'aarch64')
       # pwr7
       # powerpc64- (big-endian) is skipped because it is pre-pwr8 by default
-      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD
+      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD $REPORT_TIME
         env:
           RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -C target-cpu=pwr7
           RUSTFLAGS: ${{ env.RUSTFLAGS }} -C target-cpu=pwr7
         if: startsWith(matrix.target, 'powerpc64le-')
       # pwr8
       # powerpc64le- (little-endian) is skipped because it is pwr8 by default
-      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD
+      - run: tools/test.sh -vv $TARGET $DOCTEST_XCOMPILE $BUILD_STD $REPORT_TIME
         env:
           RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -C target-cpu=pwr8
           RUSTFLAGS: ${{ env.RUSTFLAGS }} -C target-cpu=pwr8
@@ -303,8 +312,7 @@ jobs:
       - run: sudo apt-get -o Acquire::Retries=10 -qq update && sudo apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends moreutils
       - run: echo "TARGET=--target=${{ matrix.target }}" >>"${GITHUB_ENV}"
         if: matrix.target != ''
-      - run: |
-          cargo miri test --workspace --all-features $EXCLUDE $TARGET 2>&1 | ts -i '%.s  '
+      - run: cargo miri test --workspace --all-features $EXCLUDE $TARGET 2>&1 | ts -i '%.s  '
         env:
           MIRIFLAGS: -Zmiri-strict-provenance -Zmiri-symbolic-alignment-check -Zmiri-retag-fields -Zmiri-disable-isolation
           RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -Z randomize-layout
@@ -351,7 +359,7 @@ jobs:
 
   valgrind:
     env:
-      CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER: valgrind -v --error-exitcode=1 --error-limit=no --leak-check=full --show-leak-kinds=all --track-origins=yes
+      VALGRIND: valgrind
     runs-on: ubuntu-latest
     timeout-minutes: 60
     steps:
@@ -360,17 +368,14 @@ jobs:
           persist-credentials: false
       - name: Install Rust
         run: rustup toolchain add nightly --no-self-update --component rust-src && rustup default nightly
+      - run: sudo apt-get -o Acquire::Retries=10 -qq update && sudo apt-get -o Acquire::Retries=10 -o Dpkg::Use-Pty=0 install -y --no-install-recommends moreutils
       - uses: taiki-e/install-action@valgrind
-      # doctests on Valgrind are very slow
-      - run: tools/test.sh -vv --tests
-        env:
-          RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} --cfg valgrind
-          RUSTFLAGS: ${{ env.RUSTFLAGS }} --cfg valgrind
+      - run: tools/test.sh -vv 2>&1 | ts -i '%.s  '
       # +cmpxchg16b
-      - run: tools/test.sh -vv --tests
+      - run: tools/test.sh -vv 2>&1 | ts -i '%.s  '
         env:
-          RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -C target-feature=+cmpxchg16b --cfg valgrind
-          RUSTFLAGS: ${{ env.RUSTFLAGS }} -C target-feature=+cmpxchg16b --cfg valgrind
+          RUSTDOCFLAGS: ${{ env.RUSTDOCFLAGS }} -C target-feature=+cmpxchg16b
+          RUSTFLAGS: ${{ env.RUSTFLAGS }} -C target-feature=+cmpxchg16b
 
   codegen:
     runs-on: ubuntu-latest

diff --git a/Cargo.toml b/Cargo.toml
@@ -67,7 +67,6 @@ crossbeam-utils = "0.8"
 fastrand = "1"
 paste = "1"
 quickcheck = { default-features = false, git = "https://github.com/taiki-e/quickcheck.git", branch = "dev" } # https://github.com/BurntSushi/quickcheck/pull/304 + https://github.com/BurntSushi/quickcheck/pull/282 + lower MSRV
-rustversion = "1"
 serde_test = "1"
 sptr = "0.3"
 static_assertions = "1"
diff --git a/bench/Cargo.toml b/bench/Cargo.toml
@@ -19,7 +19,6 @@ crossbeam-utils = "0.8"
 fastrand = "1"
 paste = "1"
 quickcheck = { default-features = false, git = "https://github.com/taiki-e/quickcheck.git", branch = "dev" }  # https://github.com/BurntSushi/quickcheck/pull/304 + https://github.com/BurntSushi/quickcheck/pull/282 + lower MSRV
-rustversion = "1"
 static_assertions = "1"
 
 [[bench]]

diff --git a/src/imp/arm_linux.rs b/src/imp/arm_linux.rs
@@ -16,7 +16,7 @@ mod fallback;
 
 #[cfg(not(portable_atomic_no_asm))]
 use core::arch::asm;
-use core::{mem, sync::atomic::Ordering};
+use core::{cell::UnsafeCell, mem, sync::atomic::Ordering};
 
 /// A 64-bit value represented as a pair of 32-bit values.
 ///
@@ -56,10 +56,17 @@ fn __kuser_helper_version() -> i32 {
 }
 #[inline]
 fn has_kuser_cmpxchg64() -> bool {
+    // Note: This cfg is intended to make it easy for portable-atomic developers
+    // to test __kuser_helper_version < 5 cases, and is not a public API.
+    if cfg!(portable_atomic_test_outline_atomics_detect_false) {
+        return false;
+    }
     __kuser_helper_version() >= 5
 }
 #[inline]
 unsafe fn __kuser_cmpxchg64(old_val: *const u64, new_val: *const u64, ptr: *mut u64) -> bool {
+    debug_assert!(ptr as usize % 8 == 0);
+    debug_assert!(has_kuser_cmpxchg64());
     // SAFETY: the caller must uphold the safety contract.
     unsafe {
         let f: extern "C" fn(*const u64, *const u64, *mut u64) -> u32 =
@@ -91,9 +98,6 @@ unsafe fn atomic_update_kuser_cmpxchg64<F>(dst: *mut u64, mut f: F) -> u64
 where
     F: FnMut(u64) -> u64,
 {
-    debug_assert!(dst as usize % 8 == 0);
-    debug_assert!(has_kuser_cmpxchg64());
-
     // SAFETY: the caller must uphold the safety contract.
     unsafe {
         loop {
@@ -130,7 +134,7 @@ macro_rules! atomic_with_ifunc {
                     if has_kuser_cmpxchg64() {
                         kuser_cmpxchg64_fn
                     } else {
-                        // Use SeqCst because __kuser_cmpxchg64 is SeqCst.
+                        // Use SeqCst because __kuser_cmpxchg64 is always SeqCst.
                         // https://github.com/torvalds/linux/blob/v6.1/arch/arm/kernel/entry-armv.S#L918-L925
                         fallback::$seqcst_fallback_fn
                     }
@@ -264,7 +268,7 @@ macro_rules! atomic64 {
     ($atomic_type:ident, $int_type:ident, $atomic_max:ident, $atomic_min:ident) => {
         #[repr(C, align(8))]
         pub(crate) struct $atomic_type {
-            v: core::cell::UnsafeCell<$int_type>,
+            v: UnsafeCell<$int_type>,
         }
 
         // Send is implicitly implemented.
@@ -276,7 +280,7 @@ macro_rules! atomic64 {
         impl $atomic_type {
             #[inline]
             pub(crate) const fn new(v: $int_type) -> Self {
-                Self { v: core::cell::UnsafeCell::new(v) }
+                Self { v: UnsafeCell::new(v) }
             }
 
             #[inline]