147 lines
4.6 KiB
Rust
147 lines
4.6 KiB
Rust
use int::LargeInt;
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use int::Int;
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macro_rules! mul {
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($intrinsic:ident: $ty:ty) => {
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/// Returns `a * b`
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#[cfg_attr(not(test), no_mangle)]
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pub extern "C" fn $intrinsic(a: $ty, b: $ty) -> $ty {
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let half_bits = <$ty>::bits() / 4;
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let lower_mask = !0 >> half_bits;
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let mut low = (a.low() & lower_mask).wrapping_mul(b.low() & lower_mask);
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let mut t = low >> half_bits;
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low &= lower_mask;
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t += (a.low() >> half_bits).wrapping_mul(b.low() & lower_mask);
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low += (t & lower_mask) << half_bits;
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let mut high = (t >> half_bits) as hty!($ty);
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t = low >> half_bits;
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low &= lower_mask;
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t += (b.low() >> half_bits).wrapping_mul(a.low() & lower_mask);
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low += (t & lower_mask) << half_bits;
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high += (t >> half_bits) as hty!($ty);
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high += (a.low() >> half_bits).wrapping_mul(b.low() >> half_bits) as hty!($ty);
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high = high.wrapping_add(a.high().wrapping_mul(b.low() as hty!($ty)))
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.wrapping_add((a.low() as hty!($ty)).wrapping_mul(b.high()));
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<$ty>::from_parts(low, high)
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}
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}
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}
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macro_rules! mulo {
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($intrinsic:ident: $ty:ty) => {
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// Default is "C" ABI
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mulo!($intrinsic: $ty, "C");
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};
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($intrinsic:ident: $ty:ty, $abi:tt) => {
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/// Returns `a * b` and sets `*overflow = 1` if `a * b` overflows
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#[cfg_attr(not(test), no_mangle)]
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pub extern $abi fn $intrinsic(a: $ty, b: $ty, overflow: &mut i32) -> $ty {
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*overflow = 0;
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let result = a.wrapping_mul(b);
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if a == <$ty>::min_value() {
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if b != 0 && b != 1 {
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*overflow = 1;
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}
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return result;
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}
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if b == <$ty>::min_value() {
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if a != 0 && a != 1 {
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*overflow = 1;
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}
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return result;
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}
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let sa = a >> (<$ty>::bits() - 1);
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let abs_a = (a ^ sa) - sa;
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let sb = b >> (<$ty>::bits() - 1);
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let abs_b = (b ^ sb) - sb;
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if abs_a < 2 || abs_b < 2 {
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return result;
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}
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if sa == sb {
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if abs_a > <$ty>::max_value() / abs_b {
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*overflow = 1;
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}
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} else {
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if abs_a > <$ty>::min_value() / -abs_b {
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*overflow = 1;
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}
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}
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result
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}
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}
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}
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#[cfg(not(all(feature = "c", target_arch = "x86")))]
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mul!(__muldi3: u64);
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mul!(__multi3: i128);
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mulo!(__mulosi4: i32);
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mulo!(__mulodi4: i64);
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#[cfg(all(windows, target_pointer_width="64"))]
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mulo!(__muloti4: i128, "unadjusted");
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#[cfg(not(all(windows, target_pointer_width="64")))]
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mulo!(__muloti4: i128);
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#[cfg(test)]
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mod tests {
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use qc::{I32, I64, U64};
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check! {
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fn __muldi3(f: extern fn(u64, u64) -> u64, a: U64, b: U64)
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-> Option<u64> {
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Some(f(a.0, b.0))
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}
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fn __mulosi4(f: extern fn(i32, i32, &mut i32) -> i32,
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a: I32,
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b: I32) -> Option<(i32, i32)> {
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let (a, b) = (a.0, b.0);
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let mut overflow = 2;
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let r = f(a, b, &mut overflow);
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if overflow != 0 && overflow != 1 {
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panic!("Invalid value {} for overflow", overflow);
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}
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Some((r, overflow))
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}
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fn __mulodi4(f: extern fn(i64, i64, &mut i32) -> i64,
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a: I64,
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b: I64) -> Option<(i64, i32)> {
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let (a, b) = (a.0, b.0);
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let mut overflow = 2;
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let r = f(a, b, &mut overflow);
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if overflow != 0 && overflow != 1 {
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panic!("Invalid value {} for overflow", overflow);
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}
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Some((r, overflow))
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}
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}
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}
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#[cfg(test)]
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#[cfg(all(not(windows), target_pointer_width="64"))]
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mod tests_i128 {
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use qc::I128;
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check! {
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fn __multi3(f: extern fn(i128, i128) -> i128, a: I128, b: I128)
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-> Option<i128> {
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Some(f(a.0, b.0))
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}
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fn __muloti4(f: extern fn(i128, i128, &mut i32) -> i128,
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a: I128,
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b: I128) -> Option<(i128, i32)> {
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let (a, b) = (a.0, b.0);
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let mut overflow = 2;
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let r = f(a, b, &mut overflow);
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if overflow != 0 && overflow != 1 {
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panic!("Invalid value {} for overflow", overflow);
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}
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Some((r, overflow))
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}
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}
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}
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