libm: Flatten the `libm/libm` directory

1 files changed, 106 insertions, 0 deletions

diff --git a/library/compiler-builtins/libm/src/math/remquo.rs b/library/compiler-builtins/libm/src/math/remquo.rs
new file mode 100644
index 00000000000..4c11e848746
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/remquo.rs
@@ -0,0 +1,106 @@
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn remquo(mut x: f64, mut y: f64) -> (f64, i32) {
+    let ux: u64 = x.to_bits();
+    let mut uy: u64 = y.to_bits();
+    let mut ex = ((ux >> 52) & 0x7ff) as i32;
+    let mut ey = ((uy >> 52) & 0x7ff) as i32;
+    let sx = (ux >> 63) != 0;
+    let sy = (uy >> 63) != 0;
+    let mut q: u32;
+    let mut i: u64;
+    let mut uxi: u64 = ux;
+
+    if (uy << 1) == 0 || y.is_nan() || ex == 0x7ff {
+        return ((x * y) / (x * y), 0);
+    }
+    if (ux << 1) == 0 {
+        return (x, 0);
+    }
+
+    /* normalize x and y */
+    if ex == 0 {
+        i = uxi << 12;
+        while (i >> 63) == 0 {
+            ex -= 1;
+            i <<= 1;
+        }
+        uxi <<= -ex + 1;
+    } else {
+        uxi &= (!0) >> 12;
+        uxi |= 1 << 52;
+    }
+    if ey == 0 {
+        i = uy << 12;
+        while (i >> 63) == 0 {
+            ey -= 1;
+            i <<= 1;
+        }
+        uy <<= -ey + 1;
+    } else {
+        uy &= (!0) >> 12;
+        uy |= 1 << 52;
+    }
+
+    q = 0;
+
+    if ex + 1 != ey {
+        if ex < ey {
+            return (x, 0);
+        }
+        /* x mod y */
+        while ex > ey {
+            i = uxi.wrapping_sub(uy);
+            if (i >> 63) == 0 {
+                uxi = i;
+                q += 1;
+            }
+            uxi <<= 1;
+            q <<= 1;
+            ex -= 1;
+        }
+        i = uxi.wrapping_sub(uy);
+        if (i >> 63) == 0 {
+            uxi = i;
+            q += 1;
+        }
+        if uxi == 0 {
+            ex = -60;
+        } else {
+            while (uxi >> 52) == 0 {
+                uxi <<= 1;
+                ex -= 1;
+            }
+        }
+    }
+
+    /* scale result and decide between |x| and |x|-|y| */
+    if ex > 0 {
+        uxi -= 1 << 52;
+        uxi |= (ex as u64) << 52;
+    } else {
+        uxi >>= -ex + 1;
+    }
+    x = f64::from_bits(uxi);
+    if sy {
+        y = -y;
+    }
+    if ex == ey || (ex + 1 == ey && (2.0 * x > y || (2.0 * x == y && (q % 2) != 0))) {
+        x -= y;
+        // TODO: this matches musl behavior, but it is incorrect
+        q = q.wrapping_add(1);
+    }
+    q &= 0x7fffffff;
+    let quo = if sx ^ sy { -(q as i32) } else { q as i32 };
+    if sx { (-x, quo) } else { (x, quo) }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::remquo;
+
+    #[test]
+    fn test_q_overflow() {
+        // 0xc000000000000001, 0x04c0000000000004
+        let _ = remquo(-2.0000000000000004, 8.406091369059082e-286);
+    }
+}