compiler_builtins/int/
mul.rs

1use crate::int::{DInt, HInt, Int};
2
3trait Mul: DInt + Int
4where
5    Self::H: DInt,
6{
7    fn mul(self, rhs: Self) -> Self {
8        // In order to prevent infinite recursion, we cannot use the `widen_mul` in this:
9        //self.lo().widen_mul(rhs.lo())
10        //    .wrapping_add(self.lo().wrapping_mul(rhs.hi()).widen_hi())
11        //    .wrapping_add(self.hi().wrapping_mul(rhs.lo()).widen_hi())
12
13        let lhs_lo = self.lo();
14        let rhs_lo = rhs.lo();
15        // construct the widening multiplication using only `Self::H` sized multiplications
16        let tmp_0 = lhs_lo.lo().zero_widen_mul(rhs_lo.lo());
17        let tmp_1 = lhs_lo.lo().zero_widen_mul(rhs_lo.hi());
18        let tmp_2 = lhs_lo.hi().zero_widen_mul(rhs_lo.lo());
19        let tmp_3 = lhs_lo.hi().zero_widen_mul(rhs_lo.hi());
20        // sum up all widening partials
21        let mul = Self::from_lo_hi(tmp_0, tmp_3)
22            .wrapping_add(tmp_1.zero_widen() << (Self::BITS / 4))
23            .wrapping_add(tmp_2.zero_widen() << (Self::BITS / 4));
24        // add the higher partials
25        mul.wrapping_add(lhs_lo.wrapping_mul(rhs.hi()).widen_hi())
26            .wrapping_add(self.hi().wrapping_mul(rhs_lo).widen_hi())
27    }
28}
29
30impl Mul for u64 {}
31impl Mul for i128 {}
32
33pub(crate) trait UMulo: DInt + Int {
34    fn mulo(self, rhs: Self) -> (Self, bool) {
35        match (self.hi().is_zero(), rhs.hi().is_zero()) {
36            // overflow is guaranteed
37            (false, false) => (self.wrapping_mul(rhs), true),
38            (true, false) => {
39                let mul_lo = self.lo().widen_mul(rhs.lo());
40                let mul_hi = self.lo().widen_mul(rhs.hi());
41                let (mul, o) = mul_lo.overflowing_add(mul_hi.lo().widen_hi());
42                (mul, o || !mul_hi.hi().is_zero())
43            }
44            (false, true) => {
45                let mul_lo = rhs.lo().widen_mul(self.lo());
46                let mul_hi = rhs.lo().widen_mul(self.hi());
47                let (mul, o) = mul_lo.overflowing_add(mul_hi.lo().widen_hi());
48                (mul, o || !mul_hi.hi().is_zero())
49            }
50            // overflow is guaranteed to not happen, and use a smaller widening multiplication
51            (true, true) => (self.lo().widen_mul(rhs.lo()), false),
52        }
53    }
54}
55
56impl UMulo for u32 {}
57impl UMulo for u64 {}
58impl UMulo for u128 {}
59
60macro_rules! impl_signed_mulo {
61    ($fn:ident, $iD:ident, $uD:ident) => {
62        fn $fn(lhs: $iD, rhs: $iD) -> ($iD, bool) {
63            let mut lhs = lhs;
64            let mut rhs = rhs;
65            // the test against `mul_neg` below fails without this early return
66            if lhs == 0 || rhs == 0 {
67                return (0, false);
68            }
69
70            let lhs_neg = lhs < 0;
71            let rhs_neg = rhs < 0;
72            if lhs_neg {
73                lhs = lhs.wrapping_neg();
74            }
75            if rhs_neg {
76                rhs = rhs.wrapping_neg();
77            }
78            let mul_neg = lhs_neg != rhs_neg;
79
80            let (mul, o) = (lhs as $uD).mulo(rhs as $uD);
81            let mut mul = mul as $iD;
82
83            if mul_neg {
84                mul = mul.wrapping_neg();
85            }
86            if (mul < 0) != mul_neg {
87                // this one check happens to catch all edge cases related to `$iD::MIN`
88                (mul, true)
89            } else {
90                (mul, o)
91            }
92        }
93    };
94}
95
96impl_signed_mulo!(i32_overflowing_mul, i32, u32);
97impl_signed_mulo!(i64_overflowing_mul, i64, u64);
98impl_signed_mulo!(i128_overflowing_mul, i128, u128);
99
100intrinsics! {
101    #[maybe_use_optimized_c_shim]
102    #[arm_aeabi_alias = __aeabi_lmul]
103    #[cfg(any(not(any(target_arch = "riscv32", target_arch = "riscv64")), target_feature = "m"))]
104    pub extern "C" fn __muldi3(a: u64, b: u64) -> u64 {
105        a.mul(b)
106    }
107
108    pub extern "C" fn __multi3(a: i128, b: i128) -> i128 {
109        a.mul(b)
110    }
111
112    pub extern "C" fn __mulosi4(a: i32, b: i32, oflow: &mut i32) -> i32 {
113        let (mul, o) = i32_overflowing_mul(a, b);
114        *oflow = o as i32;
115        mul
116    }
117
118    pub extern "C" fn __mulodi4(a: i64, b: i64, oflow: &mut i32) -> i64 {
119        let (mul, o) = i64_overflowing_mul(a, b);
120        *oflow = o as i32;
121        mul
122    }
123
124    #[unadjusted_on_win64]
125    pub extern "C" fn __muloti4(a: i128, b: i128, oflow: &mut i32) -> i128 {
126        let (mul, o) = i128_overflowing_mul(a, b);
127        *oflow = o as i32;
128        mul
129    }
130
131    pub extern "C" fn __rust_i128_mulo(a: i128, b: i128, oflow: &mut i32) -> i128 {
132        let (mul, o) = i128_overflowing_mul(a, b);
133        *oflow = o.into();
134        mul
135    }
136
137    pub extern "C" fn __rust_u128_mulo(a: u128, b: u128, oflow: &mut i32) -> u128 {
138        let (mul, o) = a.mulo(b);
139        *oflow = o.into();
140        mul
141    }
142}
compiler_builtins/int/mul.rs

compiler_builtins/int/
mul.rs
