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Goldilocks: better constant propagation through add_with_wraparound (#320)

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This commit is contained in:
Jakub Nabaglo 2021-10-22 15:02:22 -07:00 committed by GitHub
parent c406f464b8
commit db23416b04
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2 changed files with 14 additions and 0 deletions
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4
src/field/goldilocks_field.rs
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@ -13,6 +13,7 @@ use crate::field::extension_field::quartic::QuarticExtension;
use crate::field::extension_field::Extendable;
use crate::field::field_types::{Field, PrimeField, RichField};
use crate::field::inversion::try_inverse_u64;
use crate::util::assume;
const EPSILON: u64 = (1 << 32) - 1;
@ -280,6 +281,8 @@ unsafe fn add_with_wraparound(x: u64, y: u64) -> u64 {
inlateout(reg) y => adjustment,
options(pure, nomem, nostack),
);
assume(x != 0 || (res_wrapped == y && adjustment == 0));
assume(y != 0 || (res_wrapped == x && adjustment == 0));
res_wrapped.wrapping_add(adjustment) // Add EPSILON == subtract ORDER.
}
@ -307,6 +310,7 @@ unsafe fn sub_with_wraparound(x: u64, y: u64) -> u64 {
inlateout(reg) y => adjustment,
options(pure, nomem, nostack),
);
assume(y != 0 || (res_wrapped == x && adjustment == 0));
res_wrapped.wrapping_sub(adjustment) // Subtract EPSILON == add ORDER.
}

10
src/util/mod.rs
View File

@ -1,3 +1,5 @@
use core::hint::unreachable_unchecked;
use crate::field::field_types::Field;
use crate::polynomial::polynomial::PolynomialValues;
@ -195,6 +197,14 @@ pub(crate) fn reverse_bits(n: usize, num_bits: usize) -> usize {
.0
}
#[inline(always)]
pub(crate) unsafe fn assume(p: bool) {
debug_assert!(p);
if !p {
unreachable_unchecked();
}
}
#[cfg(test)]
mod tests {
use crate::util::{reverse_bits, reverse_index_bits, reverse_index_bits_in_place};