50 lines
1.2 KiB
Rust
50 lines
1.2 KiB
Rust
macro_rules! pow {
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($intrinsic:ident: $fty:ty, $ity:ident) => {
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/// Returns `a` raised to the power `b`
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#[cfg_attr(not(test), no_mangle)]
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pub extern "C" fn $intrinsic(a: $fty, b: $ity) -> $fty {
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let (mut a, mut b) = (a, b);
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let recip = b < 0;
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let mut r: $fty = 1.0;
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loop {
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if (b & 1) != 0 {
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r *= a;
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}
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b = sdiv!($ity, b, 2);
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if b == 0 {
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break;
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}
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a *= a;
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}
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if recip {
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1.0 / r
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} else {
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r
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}
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}
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}
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}
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pow!(__powisf2: f32, i32);
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pow!(__powidf2: f64, i32);
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#[cfg(test)]
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mod tests {
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use qc::{I32, F32, F64};
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check! {
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fn __powisf2(f: extern "C" fn(f32, i32) -> f32,
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a: F32,
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b: I32) -> Option<F32> {
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Some(F32(f(a.0, b.0)))
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}
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fn __powidf2(f: extern "C" fn(f64, i32) -> f64,
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a: F64,
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b: I32) -> Option<F64> {
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Some(F64(f(a.0, b.0)))
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}
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}
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}
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