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Const folding enums over snapshots. #7849

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104 changes: 85 additions & 19 deletions crates/cairo-lang-lowering/src/optimizations/const_folding.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -238,22 +238,32 @@ pub fn const_folding(
ctx.maybe_replace_inputs(info.inputs_mut());
match info {
MatchInfo::Enum(MatchEnumInfo { input, arms, .. }) => {
if let Some(VarInfo::Const(ConstValue::Enum(variant, value))) =
ctx.var_info.get(&input.var_id)
if let Some((
n_snapshots,
VarInfo::Const(ConstValue::Enum(variant, value)),
)) = ctx.peel_snapshots(input.var_id)
{
let arm = &arms[variant.idx];
let value = value.as_ref().clone();
let output = arm.var_ids[0];
if ctx.variables[input.var_id].droppable.is_ok()
&& ctx.variables[output].copyable.is_ok()
&& ctx
.try_generate_const_statements(
&value,
output,
n_snapshots,
&mut block.statements,
)
.is_some()
{
if let Some(stmt) = ctx.try_generate_const_statement(&value, output)
{
block.statements.push(stmt);
block.end = BlockEnd::Goto(arm.block_id, Default::default());
}
block.end = BlockEnd::Goto(arm.block_id, Default::default());
}
let mut info = VarInfo::Const(value);
for _ in 0..n_snapshots {
info = VarInfo::Snapshot(Box::new(info));
}
ctx.var_info.insert(output, VarInfo::Const(value));
ctx.var_info.insert(output, info);
}
}
MatchInfo::Value(info) => {
Expand Down Expand Up @@ -633,20 +643,65 @@ impl ConstFoldingContext<'_> {
self.propagate_const_and_get_statement(BigInt::zero(), output, false)
}

/// Returns a statement that introduces the requested value into `output`, or None if fails.
fn try_generate_const_statement(
&self,
/// Adds statements that introduces the requested value into `output` and returns `Some(())`,
/// or `None` if fails.
fn try_generate_const_statements(
&mut self,
value: &ConstValue,
output: VariableId,
) -> Option<Statement> {
if self.db.type_size_info(self.variables[output].ty) == Ok(TypeSizeInformation::Other) {
Some(Statement::Const(StatementConst { value: value.clone(), output }))
} else if matches!(value, ConstValue::Struct(members, _) if members.is_empty()) {
// Handling const empty structs - which are not supported in sierra-gen.
Some(Statement::StructConstruct(StatementStructConstruct { inputs: vec![], output }))
} else {
None
n_snapshots: usize,
statements: &mut Vec<Statement>,
) -> Option<()> {
let var = &self.variables[output];
let output_ty = var.ty;
let size_info = self.db.type_size_info(output_ty).ok()?;
if size_info == TypeSizeInformation::ZeroSized
&& !matches!(value, ConstValue::Struct(members, _) if members.is_empty())
{
return None;
}
let get_base_stmt = |var| {
if size_info == TypeSizeInformation::ZeroSized {
Statement::StructConstruct(StatementStructConstruct { inputs: vec![], output: var })
} else {
Statement::Const(StatementConst { value: value.clone(), output: var })
}
};
if n_snapshots == 0 {
statements.push(get_base_stmt(output));
return Some(());
}
let location = var.location;
let mut curr_ty = value.ty(self.db).ok()?;
let mut new_var = |ty| {
self.variables.alloc(Variable::new(self.db, ImplLookupContext::default(), ty, location))
};
let mut curr_var = new_var(curr_ty);
statements.push(get_base_stmt(curr_var));
for _ in 1..n_snapshots {
let unused_orig = new_var(curr_ty);
let snapped_ty = TypeLongId::Snapshot(curr_ty).intern(self.db);
let snapped_var = new_var(snapped_ty);
statements.push(Statement::Snapshot(StatementSnapshot {
input: VarUsage { var_id: curr_var, location },
outputs: [unused_orig, snapped_var],
}));
curr_ty = snapped_ty;
curr_var = snapped_var;
}
let unused_orig = new_var(curr_ty);
statements.push(Statement::Snapshot(StatementSnapshot {
input: VarUsage { var_id: curr_var, location },
outputs: [unused_orig, output],
}));
let final_ty = TypeLongId::Snapshot(curr_ty).intern(self.db);
assert!(
final_ty == output_ty,
"{} != {}",
final_ty.format(self.db),
output_ty.format(self.db)
);
Some(())
}

/// Handles the end of an extern block.
Expand Down Expand Up @@ -990,6 +1045,17 @@ impl ConstFoldingContext<'_> {
try_extract_matches!(self.var_info.get(&var_id)?, VarInfo::Const)
}

/// Returns the number of snapshots and the `VarInfo` wrapped by the snapshots.
fn peel_snapshots(&self, var_id: VariableId) -> Option<(usize, &VarInfo)> {
let mut n_snapshots = 0;
let mut curr = self.var_info.get(&var_id)?;
while let VarInfo::Snapshot(next) = curr {
n_snapshots += 1;
curr = next.as_ref();
}
Some((n_snapshots, curr))
}

/// Return the const value as an int if it exists and is an integer, additionally, if it is of a
/// non-zero type.
fn as_int_ex(&self, var_id: VariableId) -> Option<(&BigInt, bool)> {
Expand Down
169 changes: 169 additions & 0 deletions crates/cairo-lang-lowering/src/optimizations/test_data/const_folding
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5903,3 +5903,172 @@ End:
Return(v7)

//! > lowering_diagnostics

//! > ==========================================================================

//! > Match enum const.

//! > test_runner_name
test_match_optimizer

//! > function
fn foo() -> u8 {
match E::V1(2) {
E::V0(x) => x,
E::V1(x) => x,
}
}

//! > function_name
foo

//! > module_code
#[derive(Drop)]
enum E {
V0: u8,
V1: u8,
}

//! > semantic_diagnostics

//! > before
Parameters:
blk0 (root):
Statements:
(v0: core::integer::u8) <- 2
(v1: test::E) <- E::V1(v0)
End:
Match(match_enum(v1) {
E::V0(v2) => blk1,
E::V1(v3) => blk2,
})

blk1:
Statements:
End:
Goto(blk3, {v2 -> v4})

blk2:
Statements:
End:
Goto(blk3, {v3 -> v4})

blk3:
Statements:
End:
Return(v4)

//! > after
Parameters:
blk0 (root):
Statements:
(v0: core::integer::u8) <- 2
(v1: test::E) <- E::V1(v0)
(v3: core::integer::u8) <- 2
End:
Goto(blk2, {})

blk1:
Statements:
End:
Goto(blk3, {v2 -> v4})

blk2:
Statements:
End:
Goto(blk3, {v3 -> v4})

blk3:
Statements:
End:
Return(v4)

//! > lowering_diagnostics

//! > ==========================================================================

//! > Match enum snapshot const.

//! > test_runner_name
test_match_optimizer

//! > function
fn foo() -> u8 {
match @E::V1(2) {
E::V0(x) => *x,
E::V1(x) => *x,
}
}

//! > function_name
foo

//! > module_code
#[derive(Drop)]
enum E {
V0: u8,
V1: u8,
}

//! > semantic_diagnostics

//! > before
Parameters:
blk0 (root):
Statements:
(v0: core::integer::u8) <- 2
(v1: test::E) <- E::V1(v0)
(v2: test::E, v3: @test::E) <- snapshot(v1)
End:
Match(match_enum(v3) {
E::V0(v4) => blk1,
E::V1(v5) => blk2,
})

blk1:
Statements:
(v6: core::integer::u8) <- desnap(v4)
End:
Goto(blk3, {v6 -> v7})

blk2:
Statements:
(v8: core::integer::u8) <- desnap(v5)
End:
Goto(blk3, {v8 -> v7})

blk3:
Statements:
End:
Return(v7)

//! > after
Parameters:
blk0 (root):
Statements:
(v0: core::integer::u8) <- 2
(v1: test::E) <- E::V1(v0)
(v2: test::E, v3: @test::E) <- snapshot(v1)
(v9: core::integer::u8) <- 2
(v10: core::integer::u8, v5: @core::integer::u8) <- snapshot(v9)
End:
Goto(blk2, {})

blk1:
Statements:
(v6: core::integer::u8) <- desnap(v4)
End:
Goto(blk3, {v6 -> v7})

blk2:
Statements:
(v8: core::integer::u8) <- desnap(v5)
End:
Goto(blk3, {v8 -> v7})

blk3:
Statements:
End:
Return(v7)

//! > lowering_diagnostics
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