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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
// ----------------------------------------------------------------------------
// Subtract modulo m, z := (x - y) mod m, assuming x and y reduced
// Inputs x[k], y[k], m[k]; output z[k]
//
// extern void bignum_modsub(uint64_t k, uint64_t *z, const uint64_t *x,
// const uint64_t *y, const uint64_t *m);
//
// Standard x86-64 ABI: RDI = k, RSI = z, RDX = x, RCX = y, R8 = m
// Microsoft x64 ABI: RCX = k, RDX = z, R8 = x, R9 = y, [RSP+40] = m
// ----------------------------------------------------------------------------
macro_rules! k {
() => {
"rdi"
};
}
macro_rules! z {
() => {
"rsi"
};
}
macro_rules! x {
() => {
"rdx"
};
}
macro_rules! y {
() => {
"rcx"
};
}
macro_rules! m {
() => {
"r8"
};
}
macro_rules! i {
() => {
"r9"
};
}
macro_rules! j {
() => {
"r10"
};
}
macro_rules! a {
() => {
"rax"
};
}
macro_rules! c {
() => {
"r11"
};
}
/// Subtract modulo m, z := (x - y) mod m, assuming x and y reduced
///
/// Inputs x[k], y[k], m[k]; output z[k]
pub(crate) fn bignum_modsub(z: &mut [u64], x: &[u64], y: &[u64], m: &[u64]) {
debug_assert!(z.len() == x.len());
debug_assert!(z.len() == y.len());
debug_assert!(z.len() == m.len());
// SAFETY: inline assembly. see [crate::low::inline_assembly_safety] for safety info.
unsafe {
core::arch::asm!(
Q!(" endbr64 " ),
// If k = 0 do nothing
Q!(" test " k!() ", " k!()),
Q!(" jz " Label!("bignum_modsub_end", 2, After)),
// Subtract z := x - y and record a mask for the carry x - y < 0
Q!(" xor " c!() ", " c!()),
Q!(" mov " j!() ", " k!()),
Q!(" xor " i!() ", " i!()),
Q!(Label!("bignum_modsub_subloop", 3) ":"),
Q!(" mov " a!() ", [" x!() "+ 8 * " i!() "]"),
Q!(" sbb " a!() ", [" y!() "+ 8 * " i!() "]"),
Q!(" mov " "[" z!() "+ 8 * " i!() "], " a!()),
Q!(" inc " i!()),
Q!(" dec " j!()),
Q!(" jnz " Label!("bignum_modsub_subloop", 3, Before)),
Q!(" sbb " c!() ", " c!()),
// Now do a masked addition z := z + [c] * m
Q!(" xor " i!() ", " i!()),
Q!(Label!("bignum_modsub_addloop", 4) ":"),
Q!(" mov " a!() ", [" m!() "+ 8 * " i!() "]"),
Q!(" and " a!() ", " c!()),
Q!(" neg " j!()),
Q!(" adc " "[" z!() "+ 8 * " i!() "], " a!()),
Q!(" sbb " j!() ", " j!()),
Q!(" inc " i!()),
Q!(" cmp " i!() ", " k!()),
Q!(" jc " Label!("bignum_modsub_addloop", 4, Before)),
Q!(Label!("bignum_modsub_end", 2) ":"),
inout("rdi") z.len() => _,
inout("rsi") z.as_mut_ptr() => _,
inout("rdx") x.as_ptr() => _,
inout("rcx") y.as_ptr() => _,
inout("r8") m.as_ptr() => _,
// clobbers
out("r10") _,
out("r11") _,
out("r9") _,
out("rax") _,
)
};
}