1 files changed, 35 insertions, 0 deletions
diff --git a/library/compiler-builtins/libm/src/math/modf.rs b/library/compiler-builtins/libm/src/math/modf.rs
new file mode 100644
index 00000000000..6541862cdd9
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/modf.rs
@@ -0,0 +1,35 @@
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn modf(x: f64) -> (f64, f64) {
+    let rv2: f64;
+    let mut u = x.to_bits();
+    let mask: u64;
+    let e = (((u >> 52) & 0x7ff) as i32) - 0x3ff;
+
+    /* no fractional part */
+    if e >= 52 {
+        rv2 = x;
+        if e == 0x400 && (u << 12) != 0 {
+            /* nan */
+            return (x, rv2);
+        }
+        u &= 1 << 63;
+        return (f64::from_bits(u), rv2);
+    }
+
+    /* no integral part*/
+    if e < 0 {
+        u &= 1 << 63;
+        rv2 = f64::from_bits(u);
+        return (x, rv2);
+    }
+
+    mask = ((!0) >> 12) >> e;
+    if (u & mask) == 0 {
+        rv2 = x;
+        u &= 1 << 63;
+        return (f64::from_bits(u), rv2);
+    }
+    u &= !mask;
+    rv2 = f64::from_bits(u);
+    return (x - rv2, rv2);
+}