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ed25519: tune AVX2 field multiplication codegen #26

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ed25519: tune AVX2 field multiplication codegen #26

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49 changes: 33 additions & 16 deletions curve25519/solana-ed25519/src/backend/vector/avx2/field.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -792,6 +792,28 @@ impl Mul<&FieldElement2625x4> for &FieldElement2625x4 {
x.mul32(y).into()
}

#[inline(always)]
fn twice(x: u32x8) -> u32x8 {
x + x
}

#[inline(always)]
#[allow(clippy::too_many_arguments)]
fn sum10(
a: u64x4,
b: u64x4,
c: u64x4,
d: u64x4,
e: u64x4,
f: u64x4,
g: u64x4,
h: u64x4,
i: u64x4,
j: u64x4,
) -> u64x4 {
((a + b) + (c + d)) + ((e + f) + (g + h)) + (i + j)
}

let (x0, x1) = unpack_pair(self.0[0]);
let (x2, x3) = unpack_pair(self.0[1]);
let (x4, x5) = unpack_pair(self.0[2]);
Expand All @@ -816,22 +838,17 @@ impl Mul<&FieldElement2625x4> for &FieldElement2625x4 {
let y8_19 = m_lo(v19, y8);
let y9_19 = m_lo(v19, y9);

let x1_2 = x1 + x1; // This fits in a u32 iff 25 + b + 1 < 32
let x3_2 = x3 + x3; // iff b < 6
let x5_2 = x5 + x5;
let x7_2 = x7 + x7;
let x9_2 = x9 + x9;

let z0 = m(x0, y0) + m(x1_2, y9_19) + m(x2, y8_19) + m(x3_2, y7_19) + m(x4, y6_19) + m(x5_2, y5_19) + m(x6, y4_19) + m(x7_2, y3_19) + m(x8, y2_19) + m(x9_2, y1_19);
let z1 = m(x0, y1) + m(x1, y0) + m(x2, y9_19) + m(x3, y8_19) + m(x4, y7_19) + m(x5, y6_19) + m(x6, y5_19) + m(x7, y4_19) + m(x8, y3_19) + m(x9, y2_19);
let z2 = m(x0, y2) + m(x1_2, y1) + m(x2, y0) + m(x3_2, y9_19) + m(x4, y8_19) + m(x5_2, y7_19) + m(x6, y6_19) + m(x7_2, y5_19) + m(x8, y4_19) + m(x9_2, y3_19);
let z3 = m(x0, y3) + m(x1, y2) + m(x2, y1) + m(x3, y0) + m(x4, y9_19) + m(x5, y8_19) + m(x6, y7_19) + m(x7, y6_19) + m(x8, y5_19) + m(x9, y4_19);
let z4 = m(x0, y4) + m(x1_2, y3) + m(x2, y2) + m(x3_2, y1) + m(x4, y0) + m(x5_2, y9_19) + m(x6, y8_19) + m(x7_2, y7_19) + m(x8, y6_19) + m(x9_2, y5_19);
let z5 = m(x0, y5) + m(x1, y4) + m(x2, y3) + m(x3, y2) + m(x4, y1) + m(x5, y0) + m(x6, y9_19) + m(x7, y8_19) + m(x8, y7_19) + m(x9, y6_19);
let z6 = m(x0, y6) + m(x1_2, y5) + m(x2, y4) + m(x3_2, y3) + m(x4, y2) + m(x5_2, y1) + m(x6, y0) + m(x7_2, y9_19) + m(x8, y8_19) + m(x9_2, y7_19);
let z7 = m(x0, y7) + m(x1, y6) + m(x2, y5) + m(x3, y4) + m(x4, y3) + m(x5, y2) + m(x6, y1) + m(x7, y0) + m(x8, y9_19) + m(x9, y8_19);
let z8 = m(x0, y8) + m(x1_2, y7) + m(x2, y6) + m(x3_2, y5) + m(x4, y4) + m(x5_2, y3) + m(x6, y2) + m(x7_2, y1) + m(x8, y0) + m(x9_2, y9_19);
let z9 = m(x0, y9) + m(x1, y8) + m(x2, y7) + m(x3, y6) + m(x4, y5) + m(x5, y4) + m(x6, y3) + m(x7, y2) + m(x8, y1) + m(x9, y0);
// Doubling odd x limbs fits in a u32 iff 25 + b + 1 < 32, i.e. b < 6.
let z0 = sum10(m(x0, y0), m(twice(x1), y9_19), m(x2, y8_19), m(twice(x3), y7_19), m(x4, y6_19), m(twice(x5), y5_19), m(x6, y4_19), m(twice(x7), y3_19), m(x8, y2_19), m(twice(x9), y1_19));
let z1 = sum10(m(x0, y1), m(x1, y0), m(x2, y9_19), m(x3, y8_19), m(x4, y7_19), m(x5, y6_19), m(x6, y5_19), m(x7, y4_19), m(x8, y3_19), m(x9, y2_19));
let z2 = sum10(m(x0, y2), m(twice(x1), y1), m(x2, y0), m(twice(x3), y9_19), m(x4, y8_19), m(twice(x5), y7_19), m(x6, y6_19), m(twice(x7), y5_19), m(x8, y4_19), m(twice(x9), y3_19));
let z3 = sum10(m(x0, y3), m(x1, y2), m(x2, y1), m(x3, y0), m(x4, y9_19), m(x5, y8_19), m(x6, y7_19), m(x7, y6_19), m(x8, y5_19), m(x9, y4_19));
let z4 = sum10(m(x0, y4), m(twice(x1), y3), m(x2, y2), m(twice(x3), y1), m(x4, y0), m(twice(x5), y9_19), m(x6, y8_19), m(twice(x7), y7_19), m(x8, y6_19), m(twice(x9), y5_19));
let z5 = sum10(m(x0, y5), m(x1, y4), m(x2, y3), m(x3, y2), m(x4, y1), m(x5, y0), m(x6, y9_19), m(x7, y8_19), m(x8, y7_19), m(x9, y6_19));
let z6 = sum10(m(x0, y6), m(twice(x1), y5), m(x2, y4), m(twice(x3), y3), m(x4, y2), m(twice(x5), y1), m(x6, y0), m(twice(x7), y9_19), m(x8, y8_19), m(twice(x9), y7_19));
let z7 = sum10(m(x0, y7), m(x1, y6), m(x2, y5), m(x3, y4), m(x4, y3), m(x5, y2), m(x6, y1), m(x7, y0), m(x8, y9_19), m(x9, y8_19));
let z8 = sum10(m(x0, y8), m(twice(x1), y7), m(x2, y6), m(twice(x3), y5), m(x4, y4), m(twice(x5), y3), m(x6, y2), m(twice(x7), y1), m(x8, y0), m(twice(x9), y9_19));
let z9 = sum10(m(x0, y9), m(x1, y8), m(x2, y7), m(x3, y6), m(x4, y5), m(x5, y4), m(x6, y3), m(x7, y2), m(x8, y1), m(x9, y0));

// The bounds on z[i] are the same as in the serial 32-bit code
// and the comment below is copied from there:
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