Cleanup

Author: tgross35

src/math/generic/fma.rs

@@ -1,37 +1,34 @@
 use super::super::fenv::{FE_TONEAREST, fegetround};
-use super::super::{CastFrom, CastInto, DFloat, Float, HFloat, Int, IntTy, MinInt};
+use super::super::{CastFrom, CastInto, DFloat, Float, HFloat, IntTy, MinInt};
 
 /// FMA implementation when a hardware-backed larger float type is available.
 pub fn fma_big<F, B>(x: F, y: F, z: F) -> F
 where
     F: Float + HFloat<D = B>,
     B: Float + DFloat<H = F>,
-    // F: Float + CastInto<B>,
-    // B: Float + CastInto<F> + CastFrom<F>,
     B::Int: CastInto<i32>,
     i32: CastFrom<i32>,
 {
     let one = IntTy::<B>::ONE;
 
-    let xy: B;
-    let result: B;
-    let mut ui: B::Int;
-    let e: i32;
-
-    xy = x.widen() * y.widen();
-    result = xy + z.widen();
-    ui = result.to_bits();
-    e = result.exp().signed();
+    let xy: B = x.widen() * y.widen();
+    let result: B = xy + z.widen();
+    let mut ui: B::Int = result.to_bits();
+    let re = result.exp();
     let zb: B = z.widen();
 
     let prec_diff = B::SIG_BITS - F::SIG_BITS;
     let excess_prec = ui & ((one << prec_diff) - one);
-    let x = one << (prec_diff - 1);
-
-    // Common case: the larger precision is fine
-    if excess_prec != x
-        || e == i32::cast_from(F::EXP_MAX)
+    let halfway = one << (prec_diff - 1);
+
+    // Common case: the larger precision is fine if...
+    // This is not a halfway case
+    if excess_prec != halfway
+        // Or the result is NaN
+        || re == B::EXP_MAX
+        // Or the result is exact
         || (result - xy == zb && result - zb == xy)
+        // Or the mode is something other than round to nearest
         || fegetround() != FE_TONEAREST
     {
         // TODO: feclearexcept