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// generated source. do not edit.
#![allow(non_upper_case_globals, unused_macros, unused_imports)]
use crate::low::macros::*;
// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT-0
// ----------------------------------------------------------------------------
// Reduce modulo group order, z := x mod n_521
// Input x[9]; output z[9]
//
// extern void bignum_mod_n521_9(uint64_t z[static 9], const uint64_t x[static 9]);
//
// Reduction is modulo the group order of the NIST curve P-521.
//
// Standard x86-64 ABI: RDI = z, RSI = x
// Microsoft x64 ABI: RCX = z, RDX = x
// ----------------------------------------------------------------------------
macro_rules! z {
() => {
"rdi"
};
}
macro_rules! x {
() => {
"rsi"
};
}
macro_rules! q {
() => {
"rdx"
};
}
macro_rules! a {
() => {
"rax"
};
}
macro_rules! c {
() => {
"rcx"
};
}
macro_rules! d {
() => {
"r8"
};
}
macro_rules! n0 {
() => {
"r9"
};
}
macro_rules! n1 {
() => {
"r10"
};
}
macro_rules! n2 {
() => {
"r11"
};
}
macro_rules! n3 {
() => {
Q!(d!())
};
}
macro_rules! ashort {
() => {
"eax"
};
}
macro_rules! cshort {
() => {
"ecx"
};
}
macro_rules! qshort {
() => {
"edx"
};
}
/// Reduce modulo group order, z := x mod n_521
///
/// Input x[9]; output z[9]
///
/// Reduction is modulo the group order of the NIST curve P-521.
pub(crate) fn bignum_mod_n521(z: &mut [u64; 9], x: &[u64; 9]) {
// SAFETY: inline assembly. see [crate::low::inline_assembly_safety] for safety info.
unsafe {
core::arch::asm!(
Q!(" endbr64 " ),
// Load the top digit, putting a bit-stuffed version in output buffer.
// The initial quotient estimate is q = h + 1 where x = 2^521 * h + t
// The last add also clears the CF and OF flags ready for the carry chain.
Q!(" mov " q!() ", [" x!() "+ 64]"),
Q!(" mov " a!() ", ~ 0x1FF"),
Q!(" or " a!() ", " q!()),
Q!(" mov " "[" z!() "+ 64], " a!()),
Q!(" shr " q!() ", 9"),
Q!(" add " q!() ", 1"),
// Now load other digits and form r = x - q * n_521 = (q * r_521 + t) - 2^521,
// which is stored in the output buffer. Thanks to the bit-stuffing at the
// start, we get r' = (q * r_521 + t) + (2^576 - 2^521) = r + 2^576 as the
// computed result including the top carry. Hence CF <=> r >= 0, while
// r' == r (mod 2^521) because things below bit 521 are uncorrupted. We
// keep the top word in the register c since we at least have that one free.
Q!(" mov " n0!() ", 0x449048e16ec79bf7"),
Q!(" mulx " c!() ", " a!() ", " n0!()),
Q!(" adcx " a!() ", [" x!() "]"),
Q!(" mov " "[" z!() "], " a!()),
Q!(" mov " n1!() ", 0xc44a36477663b851"),
Q!(" mulx " d!() ", " a!() ", " n1!()),
Q!(" adcx " a!() ", [" x!() "+ 8]"),
Q!(" adox " a!() ", " c!()),
Q!(" mov " "[" z!() "+ 8], " a!()),
Q!(" mov " n2!() ", 0x8033feb708f65a2f"),
Q!(" mulx " c!() ", " a!() ", " n2!()),
Q!(" adcx " a!() ", [" x!() "+ 16]"),
Q!(" adox " a!() ", " d!()),
Q!(" mov " "[" z!() "+ 16], " a!()),
Q!(" mov " a!() ", 0xae79787c40d06994"),
Q!(" mulx " d!() ", " a!() ", " a!()),
Q!(" adcx " a!() ", [" x!() "+ 24]"),
Q!(" adox " a!() ", " c!()),
Q!(" mov " "[" z!() "+ 24], " a!()),
Q!(" mov " ashort!() ", 5"),
Q!(" mulx " c!() ", " a!() ", " a!()),
Q!(" adcx " a!() ", [" x!() "+ 32]"),
Q!(" adox " a!() ", " d!()),
Q!(" mov " "[" z!() "+ 32], " a!()),
Q!(" mov " a!() ", " c!()),
Q!(" adox " c!() ", " c!()),
Q!(" adc " c!() ", [" x!() "+ 40]"),
Q!(" mov " "[" z!() "+ 40], " c!()),
Q!(" mov " c!() ", [" x!() "+ 48]"),
Q!(" adc " c!() ", " a!()),
Q!(" mov " "[" z!() "+ 48], " c!()),
Q!(" mov " c!() ", [" x!() "+ 56]"),
Q!(" adc " c!() ", " a!()),
Q!(" mov " "[" z!() "+ 56], " c!()),
Q!(" mov " c!() ", [" z!() "+ 64]"),
Q!(" adc " c!() ", " a!()),
// We already know r < n_521, but if it actually went negative then
// we need to add back n_521 again. Recycle q as a bitmask for r < n_521,
// and just subtract r_521 and mask rather than literally adding 2^521.
// This also gets rid of the bit-stuffing above.
Q!(" cmc " ),
Q!(" sbb " q!() ", " q!()),
Q!(" and " n0!() ", " q!()),
Q!(" and " n1!() ", " q!()),
Q!(" and " n2!() ", " q!()),
Q!(" mov " n3!() ", 0xae79787c40d06994"),
Q!(" and " n3!() ", " q!()),
Q!(" and " qshort!() ", 5"),
Q!(" sub " "[" z!() "], " n0!()),
Q!(" sbb " "[" z!() "+ 8], " n1!()),
Q!(" sbb " "[" z!() "+ 16], " n2!()),
Q!(" sbb " "[" z!() "+ 24], " n3!()),
Q!(" sbb " "[" z!() "+ 32], " q!()),
Q!(" sbb " "[" z!() "+ 40], " a!()),
Q!(" sbb " "[" z!() "+ 48], " a!()),
Q!(" sbb " "[" z!() "+ 56], " a!()),
Q!(" sbb " cshort!() ", " ashort!()),
Q!(" and " cshort!() ", 0x1FF"),
Q!(" mov " "[" z!() "+ 64], " c!()),
inout("rdi") z.as_mut_ptr() => _,
inout("rsi") x.as_ptr() => _,
// clobbers
out("r10") _,
out("r11") _,
out("r8") _,
out("r9") _,
out("rax") _,
out("rcx") _,
out("rdx") _,
)
};
}