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    // Reference: Section 5.4.4 "LDREX / STREX" of ACLE

    /// Removes the exclusive lock created by LDREX
    // Supported: v6, v6K, v7-M, v7-A, v7-R
    // Not supported: v5, v6-M
    // NOTE: there's no dedicated CLREX instruction in v6 (<v6k); to clear the exclusive monitor users
    // have to do a dummy STREX operation
    #[cfg(any(
        all(target_feature = "v6k", not(target_feature = "mclass")), // excludes v6-M
        all(target_feature = "v7", target_feature = "mclass"), // v7-M
    ))]
    pub unsafe fn __clrex() {
        extern "C" {
            #[link_name = "llvm.arm.clrex"]
            fn clrex();
        }

        clrex()
    }

    /// Executes a exclusive LDR instruction for 8 bit value.
    // Supported: v6K, v7-M, v7-A, v7-R
    // Not supported: v5, v6, v6-M
    #[cfg(
        target_feature = "v6k", // includes v7-M but excludes v6-M
    )]
    pub unsafe fn __ldrexb(p: *const u8) -> u8 {
        extern "C" {
            #[link_name = "llvm.arm.ldrex.p0i8"]
            fn ldrex8(p: *const u8) -> u32;
        }

        ldrex8(p) as u8
    }

    /// Executes a exclusive LDR instruction for 16 bit value.
    // Supported: v6K, v7-M, v7-A, v7-R, v8
    // Not supported: v5, v6, v6-M
    #[cfg(
        target_feature = "v6k", // includes v7-M but excludes v6-M
    )]
    pub unsafe fn __ldrexh(p: *const u16) -> u16 {
        extern "C" {
            #[link_name = "llvm.arm.ldrex.p0i16"]
            fn ldrex16(p: *const u16) -> u32;
        }

        ldrex16(p) as u16
    }

    /// Executes a exclusive LDR instruction for 32 bit value.
    // Supported: v6, v7-M, v6K, v7-A, v7-R, v8
    // Not supported: v5, v6-M
    #[cfg(any(
        all(target_feature = "v6", not(target_feature = "mclass")), // excludes v6-M
        all(target_feature = "v7", target_feature = "mclass"), // v7-M
    ))]
    pub unsafe fn __ldrex(p: *const u32) -> u32 {
        extern "C" {
            #[link_name = "llvm.arm.ldrex.p0i32"]
            fn ldrex32(p: *const u32) -> u32;
        }

        ldrex32(p)
    }

    /// Executes a exclusive STR instruction for 8 bit values
    ///
    /// Returns `0` if the operation succeeded, or `1` if it failed
    // supported: v6K, v7-M, v7-A, v7-R
    // Not supported: v5, v6, v6-M
    #[cfg(
        target_feature = "v6k", // includes v7-M but excludes v6-M
    )]
    pub unsafe fn __strexb(value: u32, addr: *mut u8) -> u32 {
        extern "C" {
            #[link_name = "llvm.arm.strex.p0i8"]
            fn strex8(value: u32, addr: *mut u8) -> u32;
        }

        strex8(value, addr)
    }

    /// Executes a exclusive STR instruction for 16 bit values
    ///
    /// Returns `0` if the operation succeeded, or `1` if it failed
    // Supported: v6K, v7-M, v7-A, v7-R, v8
    // Not supported: v5, v6, v6-M
    #[cfg(
        target_feature = "v6k", // includes v7-M but excludes v6-M
    )]
    pub unsafe fn __strexh(value: u16, addr: *mut u16) -> u32 {
        extern "C" {
            #[link_name = "llvm.arm.strex.p0i16"]
            fn strex16(value: u32, addr: *mut u16) -> u32;
        }

        strex16(value as u32, addr)
    }

    /// Executes a exclusive STR instruction for 32 bit values
    ///
    /// Returns `0` if the operation succeeded, or `1` if it failed
    // Supported: v6, v7-M, v6K, v7-A, v7-R, v8
    // Not supported: v5, v6-M
    #[cfg(any(
        all(target_feature = "v6", not(target_feature = "mclass")), // excludes v6-M
        all(target_feature = "v7", target_feature = "mclass"), // v7-M
    ))]
    pub unsafe fn __strex(value: u32, addr: *mut u32) -> u32 {
        extern "C" {
            #[link_name = "llvm.arm.strex.p0i32"]
            fn strex32(value: u32, addr: *mut u32) -> u32;
        }

        strex32(value, addr)
    }

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