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Rename reduce32 to reduce and have it return its result.

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This means that all FieldElement32x4 operations return values, vs mutating interior state.
This commit is contained in:
Henry de Valence 2018-06-14 15:54:36 -07:00
parent bab1ebbeb8
commit 9f5bd8c4c0
1 changed files with 14 additions and 10 deletions
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24
src/backend/avx2/field.rs
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@ -287,9 +287,10 @@ impl FieldElement32x4 {
buf[i] = u32x8::new(a_2i, b_2i, a_2i_1, b_2i_1, c_2i, d_2i, c_2i_1, d_2i_1); buf[i] = u32x8::new(a_2i, b_2i, a_2i_1, b_2i_1, c_2i, d_2i, c_2i_1, d_2i_1);
} }
let mut out = FieldElement32x4(buf); // We don't know that the original `FieldElement64`s were
out.reduce32(); // fully reduced, so the odd limbs may exceed 2^25.
return out; // Reduce them to be sure.
FieldElement32x4(buf).reduce()
} }
/// Given \\((A,B,C,D)\\), compute \\((-A,-B,-C,-D)\\), without /// Given \\((A,B,C,D)\\), compute \\((-A,-B,-C,-D)\\), without
@ -320,7 +321,9 @@ impl FieldElement32x4 {
tmp1 + tmp2 tmp1 + tmp2
} }
pub fn reduce32(&mut self) { /// Compute the reduced form of the field elements.
#[inline]
pub fn reduce(&self) -> FieldElement32x4 {
let shifts = i32x8::new(26, 26, 25, 25, 26, 26, 25, 25); let shifts = i32x8::new(26, 26, 25, 25, 26, 26, 25, 25);
let masks = u32x8::new( let masks = u32x8::new(
(1 << 26) - 1, (1 << 26) - 1,
@ -333,6 +336,7 @@ impl FieldElement32x4 {
(1 << 25) - 1, (1 << 25) - 1,
); );
// Compute the carryout of v.
let carry = |v: u32x8| -> u32x8 { let carry = |v: u32x8| -> u32x8 {
unsafe { unsafe {
use core::arch::x86_64::_mm256_srlv_epi32; use core::arch::x86_64::_mm256_srlv_epi32;
@ -340,6 +344,7 @@ impl FieldElement32x4 {
} }
}; };
// Swap adjacent 32-bit lanes.
let swap_lanes = |v: u32x8| -> u32x8 { let swap_lanes = |v: u32x8| -> u32x8 {
unsafe { unsafe {
use core::arch::x86_64::_mm256_shuffle_epi32; use core::arch::x86_64::_mm256_shuffle_epi32;
@ -354,7 +359,7 @@ impl FieldElement32x4 {
} }
}; };
let v = &mut self.0; let mut v = self.0;
let c10 = swap_lanes(carry(v[0])); let c10 = swap_lanes(carry(v[0]));
v[0] = (v[0] & masks) + combine(u32x8::splat(0), c10); v[0] = (v[0] & masks) + combine(u32x8::splat(0), c10);
@ -380,6 +385,8 @@ impl FieldElement32x4 {
} }
v[0] = v[0] + c9_19; v[0] = v[0] + c9_19;
FieldElement32x4(v)
} }
fn reduce64(mut z: [u64x4; 10]) -> FieldElement32x4 { fn reduce64(mut z: [u64x4; 10]) -> FieldElement32x4 {
@ -553,16 +560,13 @@ impl Neg for FieldElement32x4 {
/// The output limbs are freshly reduced. /// The output limbs are freshly reduced.
#[inline] #[inline]
fn neg(self) -> FieldElement32x4 { fn neg(self) -> FieldElement32x4 {
let mut neg = FieldElement32x4([ FieldElement32x4([
P_TIMES_16_LO - self.0[0], P_TIMES_16_LO - self.0[0],
P_TIMES_16_HI - self.0[1], P_TIMES_16_HI - self.0[1],
P_TIMES_16_HI - self.0[2], P_TIMES_16_HI - self.0[2],
P_TIMES_16_HI - self.0[3], P_TIMES_16_HI - self.0[3],
P_TIMES_16_HI - self.0[4], P_TIMES_16_HI - self.0[4],
]); ]).reduce()
neg.reduce32();
neg
} }
} }