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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
// ----------------------------------------------------------------------------
// Convert to Montgomery form z := (2^256 * x) mod p_256
// Input x[4]; output z[4]
//
// extern void bignum_tomont_p256(uint64_t z[static 4],
// const uint64_t x[static 4]);
//
// Standard ARM ABI: X0 = z, X1 = x
// ----------------------------------------------------------------------------
// ----------------------------------------------------------------------------
// Core "x |-> (2^64 * x) mod p_256" macro, with x assumed to be < p_256.
// Input is in [d4;d3;d2;d1] and output in [d3;d2;d1;d0]
// using d4 as well as t1, t2, t3 as temporaries.
// ----------------------------------------------------------------------------
macro_rules! modstep_p256 {
($d4:expr, $d3:expr, $d2:expr, $d1:expr, $d0:expr, $t1:expr, $t2:expr, $t3:expr) => { Q!(
/* Writing the input as z = 2^256 * h + 2^192 * l + t = 2^192 * hl + t, */
/* our quotient approximation is MIN ((hl + hl>>32 + 1)>>64) (2^64 - 1). */
"subs xzr, xzr, xzr;\n"
/* Set carry flag for +1 */
"extr " $t3 ", " $d4 ", " $d3 ", #32;\n"
"adcs xzr, " $d3 ", " $t3 ";\n"
"lsr " $t3 ", " $d4 ", #32;\n"
"adcs " $t3 ", " $d4 ", " $t3 ";\n"
"csetm " $d0 ", cs;\n"
"orr " $t3 ", " $t3 ", " $d0 ";\n"
/* First do [t2;t1] = 2^32 * q, which we use twice */
"lsl " $t1 ", " $t3 ", #32;\n"
"lsr " $t2 ", " $t3 ", #32;\n"
/* Add 2^224 * q to sum */
"adds " $d3 ", " $d3 ", " $t1 ";\n"
"adc " $d4 ", " $d4 ", " $t2 ";\n"
/* Accumulate [t2;t1;d0] = (2^96 - 1) * q */
"subs " $d0 ", xzr, " $t3 ";\n"
"sbcs " $t1 ", " $t1 ", xzr;\n"
"sbc " $t2 ", " $t2 ", xzr;\n"
/* Subtract (2^256 + 2^192 + 2^96 - 1) * q */
"subs " $d0 ", xzr, " $d0 ";\n"
"sbcs " $d1 ", " $d1 ", " $t1 ";\n"
"sbcs " $d2 ", " $d2 ", " $t2 ";\n"
"sbcs " $d3 ", " $d3 ", " $t3 ";\n"
"sbcs " $d4 ", " $d4 ", " $t3 ";\n"
/* Use top word as mask to correct */
"adds " $d0 ", " $d0 ", " $d4 ";\n"
"mov " $t1 ", #0x00000000ffffffff;\n"
"and " $t1 ", " $t1 ", " $d4 ";\n"
"adcs " $d1 ", " $d1 ", " $t1 ";\n"
"adcs " $d2 ", " $d2 ", xzr;\n"
"mov " $t1 ", #0xffffffff00000001;\n"
"and " $t1 ", " $t1 ", " $d4 ";\n"
"adc " $d3 ", " $d3 ", " $t1
)}
}
macro_rules! d0 {
() => {
"x2"
};
}
macro_rules! d1 {
() => {
"x3"
};
}
macro_rules! d2 {
() => {
"x4"
};
}
macro_rules! d3 {
() => {
"x5"
};
}
macro_rules! d4 {
() => {
"x6"
};
}
macro_rules! t0 {
() => {
"x1"
};
}
macro_rules! t1 {
() => {
"x7"
};
}
macro_rules! t2 {
() => {
"x8"
};
}
macro_rules! t3 {
() => {
"x9"
};
}
/// Convert to Montgomery form z := (2^256 * x) mod p_256
///
/// Input x[4]; output z[4]
pub(crate) fn bignum_tomont_p256(z: &mut [u64; 4], x: &[u64; 4]) {
// SAFETY: inline assembly. see [crate::low::inline_assembly_safety] for safety info.
unsafe {
core::arch::asm!(
// Load the input
Q!(" ldp " d0!() ", " d1!() ", [x1]"),
Q!(" ldp " d2!() ", " d3!() ", [x1, #16]"),
// Do an initial reduction to make sure this is < p_256, using just
// a copy of the bignum_mod_p256_4 code. This is needed to set up the
// invariant "input < p_256" for the main modular reduction steps.
Q!(" mov " t0!() ", #0xffffffffffffffff"),
Q!(" mov " t1!() ", #0x00000000ffffffff"),
Q!(" mov " t3!() ", #0xffffffff00000001"),
Q!(" subs " t0!() ", " d0!() ", " t0!()),
Q!(" sbcs " t1!() ", " d1!() ", " t1!()),
Q!(" sbcs " t2!() ", " d2!() ", xzr"),
Q!(" sbcs " t3!() ", " d3!() ", " t3!()),
Q!(" csel " d0!() ", " d0!() ", " t0!() ", cc"),
Q!(" csel " d1!() ", " d1!() ", " t1!() ", cc"),
Q!(" csel " d2!() ", " d2!() ", " t2!() ", cc"),
Q!(" csel " d3!() ", " d3!() ", " t3!() ", cc"),
// Successively multiply by 2^64 and reduce
modstep_p256!(d3!(), d2!(), d1!(), d0!(), d4!(), t1!(), t2!(), t3!()),
modstep_p256!(d2!(), d1!(), d0!(), d4!(), d3!(), t1!(), t2!(), t3!()),
modstep_p256!(d1!(), d0!(), d4!(), d3!(), d2!(), t1!(), t2!(), t3!()),
modstep_p256!(d0!(), d4!(), d3!(), d2!(), d1!(), t1!(), t2!(), t3!()),
// Store the result and return
Q!(" stp " d1!() ", " d2!() ", [x0]"),
Q!(" stp " d3!() ", " d4!() ", [x0, #16]"),
inout("x0") z.as_mut_ptr() => _,
inout("x1") x.as_ptr() => _,
// clobbers
out("x2") _,
out("x3") _,
out("x4") _,
out("x5") _,
out("x6") _,
out("x7") _,
out("x8") _,
out("x9") _,
)
};
}