#![cfg(not(feature = "no-asm"))]
#![allow(unused_imports)]

use core::intrinsics;

// iOS symbols have a leading underscore.
#[cfg(target_os = "ios")]
macro_rules! bl {
    ($func:literal) => {
        concat!("bl _", $func)
    };
}
#[cfg(not(target_os = "ios"))]
macro_rules! bl {
    ($func:literal) => {
        concat!("bl ", $func)
    };
}

intrinsics! {
    // NOTE This function and the ones below are implemented using assembly because they are using a
    // custom calling convention which can't be implemented using a normal Rust function.
    #[naked]
    #[cfg(not(target_env = "msvc"))]
    pub unsafe extern "C" fn __aeabi_uidivmod() {
        core::arch::asm!(
            "push {{lr}}",
            "sub sp, sp, #4",
            "mov r2, sp",
            bl!("__udivmodsi4"),
            "ldr r1, [sp]",
            "add sp, sp, #4",
            "pop {{pc}}",
            options(noreturn)
        );
    }

    #[naked]
    pub unsafe extern "C" fn __aeabi_uldivmod() {
        core::arch::asm!(
            "push {{r4, lr}}",
            "sub sp, sp, #16",
            "add r4, sp, #8",
            "str r4, [sp]",
            bl!("__udivmoddi4"),
            "ldr r2, [sp, #8]",
            "ldr r3, [sp, #12]",
            "add sp, sp, #16",
            "pop {{r4, pc}}",
            options(noreturn)
        );
    }

    #[naked]
    pub unsafe extern "C" fn __aeabi_idivmod() {
        core::arch::asm!(
            "push {{r0, r1, r4, lr}}",
            bl!("__aeabi_idiv"),
            "pop {{r1, r2}}",
            "muls r2, r2, r0",
            "subs r1, r1, r2",
            "pop {{r4, pc}}",
            options(noreturn)
        );
    }

    #[naked]
    pub unsafe extern "C" fn __aeabi_ldivmod() {
        core::arch::asm!(
            "push {{r4, lr}}",
            "sub sp, sp, #16",
            "add r4, sp, #8",
            "str r4, [sp]",
            bl!("__divmoddi4"),
            "ldr r2, [sp, #8]",
            "ldr r3, [sp, #12]",
            "add sp, sp, #16",
            "pop {{r4, pc}}",
            options(noreturn)
        );
    }

    // The following functions use weak linkage to allow users to override
    // with custom implementation.
    // FIXME: The `*4` and `*8` variants should be defined as aliases.

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memcpy(dest: *mut u8, src: *const u8, n: usize) {
        ::mem::memcpy(dest, src, n);
    }

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memcpy4(dest: *mut u8, src: *const u8, n: usize) {
        // We are guaranteed 4-alignment, so accessing at u32 is okay.
        let mut dest = dest as *mut u32;
        let mut src = src as *mut u32;
        let mut n = n;

        while n >= 4 {
            *dest = *src;
            dest = dest.offset(1);
            src = src.offset(1);
            n -= 4;
        }

        __aeabi_memcpy(dest as *mut u8, src as *const u8, n);
    }

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memcpy8(dest: *mut u8, src: *const u8, n: usize) {
        __aeabi_memcpy4(dest, src, n);
    }

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memmove(dest: *mut u8, src: *const u8, n: usize) {
        ::mem::memmove(dest, src, n);
    }

    #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memmove4(dest: *mut u8, src: *const u8, n: usize) {
        __aeabi_memmove(dest, src, n);
    }

    #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memmove8(dest: *mut u8, src: *const u8, n: usize) {
        __aeabi_memmove(dest, src, n);
    }

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memset(dest: *mut u8, n: usize, c: i32) {
        // Note the different argument order
        ::mem::memset(dest, c, n);
    }

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memset4(dest: *mut u8, n: usize, c: i32) {
        let mut dest = dest as *mut u32;
        let mut n = n;

        let byte = (c as u32) & 0xff;
        let c = (byte << 24) | (byte << 16) | (byte << 8) | byte;

        while n >= 4 {
            *dest = c;
            dest = dest.offset(1);
            n -= 4;
        }

        __aeabi_memset(dest as *mut u8, n, byte as i32);
    }

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memset8(dest: *mut u8, n: usize, c: i32) {
        __aeabi_memset4(dest, n, c);
    }

    #[cfg(not(target_os = "ios"))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memclr(dest: *mut u8, n: usize) {
        __aeabi_memset(dest, n, 0);
    }

    #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memclr4(dest: *mut u8, n: usize) {
        __aeabi_memset4(dest, n, 0);
    }

    #[cfg(not(any(target_os = "ios", target_env = "msvc")))]
    #[linkage = "weak"]
    pub unsafe extern "aapcs" fn __aeabi_memclr8(dest: *mut u8, n: usize) {
        __aeabi_memset4(dest, n, 0);
    }
}