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feat: improve SSA type-awareness in EQ and MUL instructions (#4691)
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# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

This PR adds some improvements for SSA generation for programs such as
in #4688 where we now make more use of information on casted values.

## Additional Context



## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

---------

Co-authored-by: jfecher <jake@aztecprotocol.com>
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TomAFrench and jfecher authored Apr 2, 2024
1 parent 96b8110 commit 669f1a0
Showing 1 changed file with 22 additions and 0 deletions.
22 changes: 22 additions & 0 deletions compiler/noirc_evaluator/src/ssa/ir/instruction/binary.rs
Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,12 @@ impl Binary {
let zero = dfg.make_constant(FieldElement::zero(), operand_type);
return SimplifyResult::SimplifiedTo(zero);
}
if dfg.resolve(self.lhs) == dfg.resolve(self.rhs)
&& dfg.get_value_max_num_bits(self.lhs) == 1
{
// Squaring a boolean value is a noop.
return SimplifyResult::SimplifiedTo(self.lhs);
}
}
BinaryOp::Div => {
if rhs_is_one {
Expand Down Expand Up @@ -164,6 +170,22 @@ impl Binary {
let one = dfg.make_constant(FieldElement::one(), Type::bool());
return SimplifyResult::SimplifiedTo(one);
}

if operand_type.is_unsigned() {
// If we're comparing a variable against a constant value which lies outside of the range of
// values which the variable's type can take, we can assume that the equality will be false.
let constant = lhs.or(rhs);
let non_constant = if lhs.is_some() { self.rhs } else { self.lhs };
if let Some(constant) = constant {
let max_possible_value =
2u128.pow(dfg.get_value_max_num_bits(non_constant)) - 1;
if constant > max_possible_value.into() {
let zero = dfg.make_constant(FieldElement::zero(), Type::bool());
return SimplifyResult::SimplifiedTo(zero);
}
}
}

if operand_type == Type::bool() {
// Simplify forms of `(boolean == true)` into `boolean`
if lhs_is_one {
Expand Down

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