re-structure for compiler-builtins integration

library/compiler-builtins/libm/src/math/fmodf.rs

@@ -0,0 +1,90 @@
+use core::u32;
+
+use super::isnanf;
+
+#[inline]
+pub fn fmodf(x: f32, y: f32) -> f32 {
+    let mut uxi = x.to_bits();
+    let mut uyi = y.to_bits();
+    let mut ex = (uxi >> 23 & 0xff) as i32;
+    let mut ey = (uyi >> 23 & 0xff) as i32;
+    let sx = uxi & 0x80000000;
+    let mut i;
+
+    if uyi << 1 == 0 || isnanf(y) || ex == 0xff {
+        return (x * y) / (x * y);
+    }
+
+    if uxi << 1 <= uyi << 1 {
+        if uxi << 1 == uyi << 1 {
+            return 0.0 * x;
+        }
+
+        return x;
+    }
+
+    /* normalize x and y */
+    if ex == 0 {
+        i = uxi << 9;
+        while i >> 31 == 0 {
+            ex -= 1;
+            i <<= 1;
+        }
+
+        uxi <<= -ex + 1;
+    } else {
+        uxi &= u32::MAX >> 9;
+        uxi |= 1 << 23;
+    }
+
+    if ey == 0 {
+        i = uyi << 9;
+        while i >> 31 == 0 {
+            ey -= 1;
+            i <<= 1;
+        }
+
+        uyi <<= -ey + 1;
+    } else {
+        uyi &= u32::MAX >> 9;
+        uyi |= 1 << 23;
+    }
+
+    /* x mod y */
+    while ex > ey {
+        i = uxi - uyi;
+        if i >> 31 == 0 {
+            if i == 0 {
+                return 0.0 * x;
+            }
+            uxi = i;
+        }
+        uxi <<= 1;
+
+        ex -= 1;
+    }
+
+    i = uxi - uyi;
+    if i >> 31 == 0 {
+        if i == 0 {
+            return 0.0 * x;
+        }
+        uxi = i;
+    }
+
+    while uxi >> 23 == 0 {
+        uxi <<= 1;
+        ex -= 1;
+    }
+
+    /* scale result up */
+    if ex > 0 {
+        uxi -= 1 << 23;
+        uxi |= (ex as u32) << 23;
+    } else {
+        uxi >>= -ex + 1;
+    }
+    uxi |= sx;
+
+    f32::from_bits(uxi)
+}