102 lines
2.8 KiB
Rust
102 lines
2.8 KiB
Rust
use int::Int;
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trait Div: Int {
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/// Returns `a / b`
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fn div(self, other: Self) -> Self {
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let s_a = self >> (Self::bits() - 1);
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let s_b = other >> (Self::bits() - 1);
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// NOTE it's OK to overflow here because of the `as $uty` cast below
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// This whole operation is computing the absolute value of the inputs
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// So some overflow will happen when dealing with e.g. `i64::MIN`
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// where the absolute value is `(-i64::MIN) as u64`
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let a = (self ^ s_a).wrapping_sub(s_a);
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let b = (other ^ s_b).wrapping_sub(s_b);
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let s = s_a ^ s_b;
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let r = a.unsigned().checked_div(b.unsigned())
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.unwrap_or_else(|| ::abort());
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(Self::from_unsigned(r) ^ s) - s
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}
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}
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impl Div for i32 {}
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impl Div for i64 {}
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impl Div for i128 {}
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trait Mod: Int {
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/// Returns `a % b`
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fn mod_(self, other: Self) -> Self {
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let s = other >> (Self::bits() - 1);
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// NOTE(wrapping_sub) see comment in the `div`
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let b = (other ^ s).wrapping_sub(s);
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let s = self >> (Self::bits() - 1);
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let a = (self ^ s).wrapping_sub(s);
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let r = a.unsigned().checked_rem(b.unsigned())
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.unwrap_or_else(|| ::abort());
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(Self::from_unsigned(r) ^ s) - s
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}
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}
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impl Mod for i32 {}
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impl Mod for i64 {}
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impl Mod for i128 {}
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trait Divmod: Int {
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/// Returns `a / b` and sets `*rem = n % d`
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fn divmod<F>(self, other: Self, rem: &mut Self, div: F) -> Self
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where F: Fn(Self, Self) -> Self,
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{
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let r = div(self, other);
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// NOTE won't overflow because it's using the result from the
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// previous division
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*rem = self - r.wrapping_mul(other);
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r
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}
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}
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impl Divmod for i32 {}
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impl Divmod for i64 {}
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intrinsics! {
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#[use_c_shim_if(all(target_arch = "arm", not(target_os = "ios"), not(thumbv6m)))]
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pub extern "C" fn __divsi3(a: i32, b: i32) -> i32 {
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a.div(b)
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}
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#[use_c_shim_if(target_arch = "x86")]
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pub extern "C" fn __divdi3(a: i64, b: i64) -> i64 {
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a.div(b)
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}
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#[win64_128bit_abi_hack]
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pub extern "C" fn __divti3(a: i128, b: i128) -> i128 {
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a.div(b)
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}
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#[use_c_shim_if(all(target_arch = "arm", not(target_os = "ios")))]
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pub extern "C" fn __modsi3(a: i32, b: i32) -> i32 {
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a.mod_(b)
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}
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#[use_c_shim_if(target_arch = "x86")]
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pub extern "C" fn __moddi3(a: i64, b: i64) -> i64 {
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a.mod_(b)
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}
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#[win64_128bit_abi_hack]
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pub extern "C" fn __modti3(a: i128, b: i128) -> i128 {
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a.mod_(b)
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}
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#[use_c_shim_if(all(target_arch = "arm", not(target_os = "ios")))]
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pub extern "C" fn __divmodsi4(a: i32, b: i32, rem: &mut i32) -> i32 {
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a.divmod(b, rem, |a, b| __divsi3(a, b))
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}
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#[aapcs_on_arm]
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pub extern "C" fn __divmoddi4(a: i64, b: i64, rem: &mut i64) -> i64 {
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a.divmod(b, rem, |a, b| __divdi3(a, b))
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}
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}
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