Add newlib floorf

Author: tesuji

src/math/floorf.rs

@@ -0,0 +1,78 @@
+/* sf_floor.c -- float version of s_floor.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected].
+ */
+
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+const HUGE: f32 = 1.0e30;
+
+/// Return x rounded toward -inf to integral value
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn floorf(x: f32) -> f32 {
+    // On wasm32 we know that LLVM's intrinsic will compile to an optimized
+    // `f32.floor` native instruction, so we can leverage this for both code size
+    // and speed.
+    llvm_intrinsically_optimized! {
+        #[cfg(target_arch = "wasm32")] {
+            return unsafe { ::core::intrinsics::floorf32(x) }
+        }
+    }
+
+    use super::fdlibm::{FLT_UWORD_IS_FINITE, FLT_UWORD_IS_ZERO};
+
+    let mut i0: u32 = x.to_bits();
+    let ix: u32 = i0 & 0x7fff_ffff;
+    let j0: i32 = (ix >> 23) as i32 - 0x7f;
+    let sign: bool = (i0 >> 31) != 0;
+
+    if j0 < 23 {
+        if j0 < 0 {
+            /* raise inexact if x != 0 */
+            if HUGE + x > 0.0 {
+                /* return 0*sign(x) if |x|<1 */
+                if !sign {
+                    i0 = 0;
+                } else if !FLT_UWORD_IS_ZERO(ix) {
+                    i0 = 0xbf80_0000;
+                }
+            }
+        } else {
+            let i = 0x007f_ffff >> j0;
+            if i0 & i == 0 {
+                return x; /* x is integral */
+            }
+            if HUGE + x > 0.0 {
+                /* raise inexact flag */
+                if sign {
+                    i0 += 0x0080_0000 >> j0;
+                }
+                i0 &= !i;
+            }
+        }
+    } else {
+        if !FLT_UWORD_IS_FINITE(ix) {
+            return x + x; /* inf or NaN */
+        } else {
+            return x; /* x is integral */
+        }
+    }
+    f32::from_bits(i0)
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn no_overflow() {
+        assert_eq!(super::floorf(0.5), 0.0);
+    }
+}