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chore: abstract away subtractions from OR implementation #3923

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Merged
TomAFrench merged 2 commits into from
Jan 2, 2024
Merged

chore: abstract away subtractions from OR implementation #3923

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chore: abstract away subtractions from OR implementation
TomAFrench Jan 2, 2024
439fb27
Merge branch 'master' into tf/pure-logic-or
TomAFrench Jan 2, 2024
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13 changes: 5 additions & 8 deletions compiler/noirc_evaluator/src/ssa/acir_gen/acir_ir/acir_variable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -454,14 +454,11 @@ impl AcirContext {
self.sub_var(sum, mul)
} else {
// Implement OR in terms of AND
// max - ((max - a) AND (max -b))
// Subtracting from max flips the bits, so this is effectively:
// (NOT a) NAND (NOT b)
let max = self.add_constant((1_u128 << bit_size) - 1);
let a = self.sub_var(max, lhs)?;
let b = self.sub_var(max, rhs)?;
let a_and_b = self.and_var(a, b, typ)?;
self.sub_var(max, a_and_b)
// (NOT a) NAND (NOT b) => a OR b
let a = self.not_var(lhs, typ.clone())?;
let b = self.not_var(rhs, typ.clone())?;
let a_and_b = self.and_var(a, b, typ.clone())?;
self.not_var(a_and_b, typ)
}
}

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