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sub

The function sub subtracts two field elements in the Montgomery domain.

Preconditions: 0 ≤ eval arg1 < m 0 ≤ eval arg2 < m Postconditions: eval (from_montgomery out1) mod m = (eval (from_montgomery arg1) - eval (from_montgomery arg2)) mod m 0 ≤ eval out1 < m

p256_scalar_64.sub

pub fn sub(out1: *MontgomeryDomainFieldElement, arg1: MontgomeryDomainFieldElement, arg2: MontgomeryDomainFieldElement) void

File

lib/std/crypto/pcurves/p256/p256_scalar_64.zig:881

Code

pub fn sub(out1: *MontgomeryDomainFieldElement, arg1: MontgomeryDomainFieldElement, arg2: MontgomeryDomainFieldElement) void {
    @setRuntimeSafety(mode == .debug);

    var x1: u64 = undefined;
    var x2: u1 = undefined;
    subborrowxU64(&x1, &x2, 0x0, (arg1[0]), (arg2[0]));
    var x3: u64 = undefined;
    var x4: u1 = undefined;
    subborrowxU64(&x3, &x4, x2, (arg1[1]), (arg2[1]));
    var x5: u64 = undefined;
    var x6: u1 = undefined;
    subborrowxU64(&x5, &x6, x4, (arg1[2]), (arg2[2]));
    var x7: u64 = undefined;
    var x8: u1 = undefined;
    subborrowxU64(&x7, &x8, x6, (arg1[3]), (arg2[3]));
    var x9: u64 = undefined;
    cmovznzU64(&x9, x8, @as(u64, 0x0), 0xffffffffffffffff);
    var x10: u64 = undefined;
    var x11: u1 = undefined;
    addcarryxU64(&x10, &x11, 0x0, x1, (x9 & 0xf3b9cac2fc632551));
    var x12: u64 = undefined;
    var x13: u1 = undefined;
    addcarryxU64(&x12, &x13, x11, x3, (x9 & 0xbce6faada7179e84));
    var x14: u64 = undefined;
    var x15: u1 = undefined;
    addcarryxU64(&x14, &x15, x13, x5, x9);
    var x16: u64 = undefined;
    var x17: u1 = undefined;
    addcarryxU64(&x16, &x17, x15, x7, (x9 & 0xffffffff00000000));
    out1[0] = x10;
    out1[1] = x12;
    out1[2] = x14;
    out1[3] = x16;
}