1 files changed, 67 insertions, 0 deletions
diff --git a/library/compiler-builtins/libm/src/math/rem_pio2f.rs b/library/compiler-builtins/libm/src/math/rem_pio2f.rs
new file mode 100644
index 00000000000..3c658fe3dbc
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/rem_pio2f.rs
@@ -0,0 +1,67 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/e_rem_pio2f.c */
+/*
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ * Debugged and optimized by Bruce D. Evans.
+ */
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+use core::f64;
+
+use super::rem_pio2_large;
+
+const TOINT: f64 = 1.5 / f64::EPSILON;
+
+/// 53 bits of 2/pi
+const INV_PIO2: f64 = 6.36619772367581382433e-01; /* 0x3FE45F30, 0x6DC9C883 */
+/// first 25 bits of pi/2
+const PIO2_1: f64 = 1.57079631090164184570e+00; /* 0x3FF921FB, 0x50000000 */
+/// pi/2 - pio2_1
+const PIO2_1T: f64 = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
+
+/// Return the remainder of x rem pi/2 in *y
+///
+/// use double precision for everything except passing x
+/// use __rem_pio2_large() for large x
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub(crate) fn rem_pio2f(x: f32) -> (i32, f64) {
+    let x64 = x as f64;
+
+    let mut tx: [f64; 1] = [0.];
+    let mut ty: [f64; 1] = [0.];
+
+    let ix = x.to_bits() & 0x7fffffff;
+    /* 25+53 bit pi is good enough for medium size */
+    if ix < 0x4dc90fdb {
+        /* |x| ~< 2^28*(pi/2), medium size */
+        /* Use a specialized rint() to get fn.  Assume round-to-nearest. */
+        let tmp = x64 * INV_PIO2 + TOINT;
+        // force rounding of tmp to it's storage format on x87 to avoid
+        // excess precision issues.
+        #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))]
+        let tmp = force_eval!(tmp);
+        let f_n = tmp - TOINT;
+        return (f_n as i32, x64 - f_n * PIO2_1 - f_n * PIO2_1T);
+    }
+    if ix >= 0x7f800000 {
+        /* x is inf or NaN */
+        return (0, x64 - x64);
+    }
+    /* scale x into [2^23, 2^24-1] */
+    let sign = (x.to_bits() >> 31) != 0;
+    let e0 = ((ix >> 23) - (0x7f + 23)) as i32; /* e0 = ilogb(|x|)-23, positive */
+    tx[0] = f32::from_bits(ix - (e0 << 23) as u32) as f64;
+    let n = rem_pio2_large(&tx, &mut ty, e0, 0);
+    if sign {
+        return (-n, -ty[0]);
+    }
+    (n, ty[0])
+}