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feat: mark division/modulo by constants as not requiring a predicate #7028

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feat: mark division/modulo by constants as not requiring a predicate #7028

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b8d3338
feat: mark division/modulo by constants as not requiring a predicate
TomAFrench Jan 11, 2025
f5b1521
feat: discard predicate when inverting constant fields
TomAFrench Jan 11, 2025
14cd0dc
Merge branch 'master' into tf/allow-deduplicating-division-by-constants
TomAFrench Jan 22, 2025
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13 changes: 10 additions & 3 deletions compiler/noirc_evaluator/src/acir/acir_variable.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -327,12 +327,19 @@ impl<F: AcirField, B: BlackBoxFunctionSolver<F>> AcirContext<F, B> {
let var_data = &self.vars[&var];
if let AcirVarData::Const(constant) = var_data {
// Note that this will return a 0 if the inverse is not available
let inverted_var = self.add_data(AcirVarData::Const(constant.inverse()));
let inverted_constant = constant.inverse();
let inverted_var = self.add_constant(inverted_constant);

let should_be_one = self.mul_var(inverted_var, var)?;

// Check that the inverted var is valid.
// This check prevents invalid divisions by zero.
let should_be_one = self.mul_var(inverted_var, var)?;
self.maybe_eq_predicate(should_be_one, predicate)?;
if inverted_constant.is_zero() {
self.maybe_eq_predicate(should_be_one, predicate)?;
} else {
let one = self.add_constant(F::one());
self.assert_eq_var(should_be_one, one, None)?;
}

return Ok(inverted_var);
}
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17 changes: 9 additions & 8 deletions compiler/noirc_evaluator/src/ssa/ir/instruction.rs
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Expand Up @@ -411,7 +411,7 @@
// These can fail.
Constrain(..) | ConstrainNotEqual(..) | RangeCheck { .. } => true,

// This should never be side-effectful

Check warning on line 414 in compiler/noirc_evaluator/src/ssa/ir/instruction.rs

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Unknown word (effectful)
MakeArray { .. } | Noop => false,

// Some binary math can overflow or underflow
Expand Down Expand Up @@ -511,11 +511,10 @@
match self {
Binary(binary) => {
if matches!(binary.operator, BinaryOp::Div | BinaryOp::Mod) {
if let Some(rhs) = function.dfg.get_numeric_constant(binary.rhs) {
rhs != FieldElement::zero()
} else {
false
}
function
.dfg
.get_numeric_constant(binary.rhs)
.map_or(false, |rhs| !rhs.is_zero())
} else {
true
}
Expand Down Expand Up @@ -575,11 +574,13 @@
match self {
Instruction::Binary(binary) => {
match binary.operator {
BinaryOp::Div | BinaryOp::Mod => {
// Division and modulo operations can fail if the RHS is zero but is otherwise safe.
dfg.get_numeric_constant(binary.rhs).map_or(false, |rhs| !rhs.is_zero())
}
BinaryOp::Add { unchecked: false }
| BinaryOp::Sub { unchecked: false }
| BinaryOp::Mul { unchecked: false }
| BinaryOp::Div
| BinaryOp::Mod => {
| BinaryOp::Mul { unchecked: false } => {
// Some binary math can overflow or underflow, but this is only the case
// for unsigned types (here we assume the type of binary.lhs is the same)
dfg.type_of_value(binary.rhs).is_unsigned()
Expand Down
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