diff options
| -rw-r--r-- | src/libcore/num/mod.rs | 26 |
1 files changed, 11 insertions, 15 deletions
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index 05c7e8b8de4..127f8d3b5a2 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -537,25 +537,21 @@ macro_rules! int_impl { let mut base = self; let mut acc = Self::one(); - let mut prev_base = self; - let mut base_oflo = false; - while exp > 0 { + while exp > 1 { if (exp & 1) == 1 { - if base_oflo { - // ensure overflow occurs in the same manner it - // would have otherwise (i.e. signal any exception - // it would have otherwise). - acc = acc * (prev_base * prev_base); - } else { - acc = acc * base; - } + acc = acc * base; } - prev_base = base; - let (new_base, new_base_oflo) = base.overflowing_mul(base); - base = new_base; - base_oflo = new_base_oflo; exp /= 2; + base = base * base; + } + + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + if exp == 1 { + acc = acc * base; } + acc } |