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mul.rs: use wrapping_mul not plain 

rustc in debug mode with a plain multiplication will call @llvm.umul.with.overflow.* which may call the builtin resulting in infinite recursion.
This commit is contained in:
James Duley 2017-01-02 22:57:38 +13:00 committed by GitHub
parent 0fd5e7549f
commit ee0aacf4be
1 changed files with 4 additions and 4 deletions
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8
src/int/mul.rs
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@ -9,18 +9,18 @@ macro_rules! mul {
pub extern "C" fn $intrinsic(a: $ty, b: $ty) -> $ty { pub extern "C" fn $intrinsic(a: $ty, b: $ty) -> $ty {
let half_bits = <$ty>::bits() / 4; let half_bits = <$ty>::bits() / 4;
let lower_mask = !0 >> half_bits; let lower_mask = !0 >> half_bits;
let mut low = (a.low() & lower_mask) * (b.low() & lower_mask); let mut low = (a.low() & lower_mask).wrapping_mul(b.low() & lower_mask);
let mut t = low >> half_bits; let mut t = low >> half_bits;
low &= lower_mask; low &= lower_mask;
t += (a.low() >> half_bits) * (b.low() & lower_mask); t += (a.low() >> half_bits).wrapping_mul(b.low() & lower_mask);
low += (t & lower_mask) << half_bits; low += (t & lower_mask) << half_bits;
let mut high = t >> half_bits; let mut high = t >> half_bits;
t = low >> half_bits; t = low >> half_bits;
low &= lower_mask; low &= lower_mask;
t += (b.low() >> half_bits) * (a.low() & lower_mask); t += (b.low() >> half_bits).wrapping_mul(a.low() & lower_mask);
low += (t & lower_mask) << half_bits; low += (t & lower_mask) << half_bits;
high += t >> half_bits; high += t >> half_bits;
high += (a.low() >> half_bits) * (b.low() >> half_bits); high += (a.low() >> half_bits).wrapping_mul(b.low() >> half_bits);
high = high.wrapping_add(a.high().wrapping_mul(b.low()).wrapping_add(a.low().wrapping_mul(b.high()))); high = high.wrapping_add(a.high().wrapping_mul(b.low()).wrapping_add(a.low().wrapping_mul(b.high())));
<$ty>::from_parts(low, high) <$ty>::from_parts(low, high)
} }