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Eliminate redundant round-trip casts in OpenQASM-to-Q# compilation #2990

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minestarks merged 3 commits into from
Mar 9, 2026
Merged

Eliminate redundant round-trip casts in OpenQASM-to-Q# compilation #2990

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fbf2a0a
Eliminate redundant round-trip casts in OpenQASM-to-Q# compilation
Mar 4, 2026
0e554d5
account for differing constness
Mar 4, 2026
111ddf2
Remove const bool flag from `qsc_openqasm_compiler::types::Type` (#3004)
Copilot Mar 6, 2026
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26 changes: 13 additions & 13 deletions source/compiler/qsc_openqasm_compiler/src/ast_builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1182,25 +1182,25 @@ pub(crate) fn build_unary_op_expr(op: ast::UnOp, expr: ast::Expr, prefix_span: S

pub(crate) fn map_qsharp_type_to_ast_ty(output_ty: &crate::types::Type, span: Span) -> Ty {
let mut ty = match output_ty {
crate::types::Type::Angle(_) => build_angle_ty_ident(),
crate::types::Type::Result(_) => build_path_ident_ty("Result"),
crate::types::Type::Angle => build_angle_ty_ident(),
crate::types::Type::Result => build_path_ident_ty("Result"),
crate::types::Type::Qubit => build_path_ident_ty("Qubit"),
crate::types::Type::BigInt(_) => build_path_ident_ty("BigInt"),
crate::types::Type::Int(_) => build_path_ident_ty("Int"),
crate::types::Type::Double(_) => build_path_ident_ty("Double"),
crate::types::Type::Complex(_) => build_complex_ty_ident(),
crate::types::Type::Bool(_) => build_path_ident_ty("Bool"),
crate::types::Type::ResultArray(dims, _) => build_array_type_name("Result", *dims),
crate::types::Type::BigInt => build_path_ident_ty("BigInt"),
crate::types::Type::Int => build_path_ident_ty("Int"),
crate::types::Type::Double => build_path_ident_ty("Double"),
crate::types::Type::Complex => build_complex_ty_ident(),
crate::types::Type::Bool => build_path_ident_ty("Bool"),
crate::types::Type::ResultArray(dims) => build_array_type_name("Result", *dims),
crate::types::Type::QubitArray(dims) => build_array_type_name("Qubit", *dims),
crate::types::Type::BigIntArray(dims, _) => build_array_type_name("BigInt", *dims),
crate::types::Type::IntArray(dims, _) => build_array_type_name("Int", *dims),
crate::types::Type::BigIntArray(dims) => build_array_type_name("BigInt", *dims),
crate::types::Type::IntArray(dims) => build_array_type_name("Int", *dims),
crate::types::Type::DoubleArray(dims) => build_array_type_name("Double", *dims),
crate::types::Type::BoolArray(dims, _) => build_array_type_name("Bool", *dims),
crate::types::Type::ComplexArray(dims, _) => {
crate::types::Type::BoolArray(dims) => build_array_type_name("Bool", *dims),
crate::types::Type::ComplexArray(dims) => {
let ty = build_complex_ty_ident();
wrap_array_ty_by_dims(*dims, ty)
}
crate::types::Type::AngleArray(dims, _) => {
crate::types::Type::AngleArray(dims) => {
let ty = build_angle_ty_ident();
wrap_array_ty_by_dims(*dims, ty)
}
Expand Down
110 changes: 80 additions & 30 deletions source/compiler/qsc_openqasm_compiler/src/compiler.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -329,7 +329,7 @@ impl QasmCompiler {
if let Some(inputs) = &input {
for input in inputs {
let qsharp_ty = self.map_semantic_type_to_qsharp_type(&input.ty, input.ty_span);
if matches!(qsharp_ty, crate::types::Type::Angle(..)) {
if matches!(qsharp_ty, crate::types::Type::Angle) {
let message =
"use `float` types for passing input, using `angle` types".to_string();
let kind = CompilerErrorKind::NotSupported(message, input.span);
Expand Down Expand Up @@ -504,8 +504,8 @@ impl QasmCompiler {
.map(|symbol| {
let qsharp_ty =
self.map_semantic_type_to_qsharp_type(&symbol.ty, symbol.ty_span);
if matches!(qsharp_ty, crate::types::Type::Angle(..)) {
crate::types::Type::Double(symbol.ty.is_const())
if matches!(qsharp_ty, crate::types::Type::Angle) {
crate::types::Type::Double
} else {
qsharp_ty
}
Expand Down Expand Up @@ -751,7 +751,7 @@ impl QasmCompiler {
rhs_span,
rhs_span,
rhs_span,
&crate::types::Type::ResultArray(crate::types::ArrayDimensions::One, false),
&crate::types::Type::ResultArray(crate::types::ArrayDimensions::One),
temp_var_stmt_init_expr,
);
let temp_var_expr = build_path_ident_expr("bitarray", rhs_span, rhs_span);
Expand Down Expand Up @@ -1885,6 +1885,17 @@ impl QasmCompiler {
}

fn compile_cast_expr(&mut self, cast: &Cast) -> qsast::Expr {
// Optimization: eliminate round-trip casts (e.g. Bit → UInt(1) → Bit)
let inner = unwrap_parens(&cast.expr);
if let semast::ExprKind::Cast(inner_cast) = inner.kind.as_ref()
&& Self::maps_to_same_qsharp_type(&cast.ty, &inner_cast.expr.ty)
{
let result = self.compile_expr(&inner_cast.expr);
// Wrap in parens to preserve grouping, since the removed casts
// acted as implicit grouping delimiters in the output.
return wrap_expr_in_parens(result, cast.span);
}

let expr = self.compile_expr(&cast.expr);
let cast_expr = match cast.expr.ty {
qsc_openqasm_parser::semantic::types::Type::Bit(_) => {
Expand Down Expand Up @@ -2073,7 +2084,7 @@ impl QasmCompiler {

/// Pushes an unsupported error with the supplied message.
pub fn push_unsupported_error_message<S: AsRef<str>>(&mut self, message: S, span: Span) {
let kind = CompilerErrorKind::NotSupported(message.as_ref().to_string(), span);
let kind = unsupported_err(message, span);
self.push_compiler_error(kind);
}

Expand Down Expand Up @@ -2478,6 +2489,21 @@ impl QasmCompiler {
&mut self,
ty: &qsc_openqasm_parser::semantic::types::Type,
span: Span,
) -> crate::types::Type {
let mut errors = Vec::new();
let mapped = Self::semantic_type_for_qsharp_type(ty, span, &mut errors);
for error in errors {
self.push_compiler_error(error);
}
mapped
}

/// Mapping from an `OpenQASM` semantic type to its Q# equivalent.
/// Returns the mapped type and any errors that would have been pushed.
fn semantic_type_for_qsharp_type(
ty: &qsc_openqasm_parser::semantic::types::Type,
span: Span,
errs: &mut Vec<CompilerErrorKind>,
) -> crate::types::Type {
use qsc_openqasm_parser::semantic::types::Type;
if ty.is_array()
Expand All @@ -2486,16 +2512,15 @@ impl QasmCompiler {
Some(qsc_openqasm_parser::semantic::types::ArrayDimensions::Err)
)
{
self.push_unsupported_error_message("arrays with more than 7 dimensions", span);
errs.push(unsupported_err("arrays with more than 7 dimensions", span));
return crate::types::Type::Err;
}

let is_const = ty.is_const();
match ty {
Type::Bit(_) => crate::types::Type::Result(is_const),
Type::Bit(_) => crate::types::Type::Result,
Type::Qubit => crate::types::Type::Qubit,
Type::HardwareQubit => {
self.push_unsupported_error_message("hardware qubits", span);
errs.push(unsupported_err("hardware qubits", span));
crate::types::Type::Err
}
Type::QubitArray(_) => {
Expand All @@ -2504,28 +2529,28 @@ impl QasmCompiler {
Type::Int(width, _) | Type::UInt(width, _) => {
if let Some(width) = width {
if *width > 64 {
crate::types::Type::BigInt(is_const)
crate::types::Type::BigInt
} else {
crate::types::Type::Int(is_const)
crate::types::Type::Int
}
} else {
crate::types::Type::Int(is_const)
crate::types::Type::Int
}
}
Type::Float(_, _) => crate::types::Type::Double(is_const),
Type::Angle(_, _) => crate::types::Type::Angle(is_const),
Type::Complex(_, _) => crate::types::Type::Complex(is_const),
Type::Bool(_) => crate::types::Type::Bool(is_const),
Type::Float(_, _) => crate::types::Type::Double,
Type::Angle(_, _) => crate::types::Type::Angle,
Type::Complex(_, _) => crate::types::Type::Complex,
Type::Bool(_) => crate::types::Type::Bool,
Type::Duration(_) => {
self.push_unsupported_error_message("duration type values", span);
errs.push(unsupported_err("duration type values", span));
crate::types::Type::Err
}
Type::Stretch(_) => {
self.push_unsupported_error_message("stretch type values", span);
errs.push(unsupported_err("stretch type values", span));
crate::types::Type::Err
}
Type::BitArray(_, _) => {
crate::types::Type::ResultArray(crate::types::ArrayDimensions::One, is_const)
crate::types::Type::ResultArray(crate::types::ArrayDimensions::One)
}
Type::Array(array)
if !matches!(
Expand All @@ -2546,12 +2571,12 @@ impl QasmCompiler {
}
Type::StaticArrayRef(array_ref) if array_ref.is_mutable => {
let msg = format!("mutable array references `{ty}`");
self.push_unsupported_error_message(msg, span);
errs.push(unsupported_err(msg, span));
crate::types::Type::Err
}
Type::DynArrayRef(array_ref) if array_ref.is_mutable => {
let msg = format!("mutable array references `{ty}`");
self.push_unsupported_error_message(msg, span);
errs.push(unsupported_err(msg, span));
crate::types::Type::Err
}
Type::Gate(cargs, qargs) => crate::types::Type::Gate(*cargs, *qargs),
Expand All @@ -2571,15 +2596,16 @@ impl QasmCompiler {
};
let args = args
.iter()
.map(|arg| self.map_semantic_type_to_qsharp_type(arg, Span::default()))
.map(|arg| Self::semantic_type_for_qsharp_type(arg, Span::default(), errs))
.collect::<Vec<_>>();
let return_ty = self.map_semantic_type_to_qsharp_type(return_ty, Span::default());
let return_ty =
Self::semantic_type_for_qsharp_type(return_ty, Span::default(), errs);
crate::types::Type::Callable(kind, args.into(), return_ty.into())
}
Type::Err => crate::types::Type::Err,
_ => {
let msg = format!("converting `{ty}` to Q# type");
self.push_unimplemented_error_message(msg, span);
errs.push(CompilerErrorKind::Unimplemented(msg, span));
crate::types::Type::Err
}
}
Expand All @@ -2592,13 +2618,13 @@ impl QasmCompiler {
match base_ty {
qsc_openqasm_parser::semantic::types::ArrayBaseType::Duration => unreachable!(),
qsc_openqasm_parser::semantic::types::ArrayBaseType::Bool => {
crate::types::Type::BoolArray(dims, false)
crate::types::Type::BoolArray(dims)
}
qsc_openqasm_parser::semantic::types::ArrayBaseType::Angle(_) => {
crate::types::Type::AngleArray(dims, false)
crate::types::Type::AngleArray(dims)
}
qsc_openqasm_parser::semantic::types::ArrayBaseType::Complex(_) => {
crate::types::Type::ComplexArray(dims, false)
crate::types::Type::ComplexArray(dims)
}
qsc_openqasm_parser::semantic::types::ArrayBaseType::Float(_) => {
crate::types::Type::DoubleArray(dims)
Expand All @@ -2607,17 +2633,28 @@ impl QasmCompiler {
| qsc_openqasm_parser::semantic::types::ArrayBaseType::UInt(width) => {
if let Some(width) = width {
if *width > 64 {
crate::types::Type::BigIntArray(dims, false)
crate::types::Type::BigIntArray(dims)
} else {
crate::types::Type::IntArray(dims, false)
crate::types::Type::IntArray(dims)
}
} else {
crate::types::Type::IntArray(dims, false)
crate::types::Type::IntArray(dims)
}
}
}
}

/// Returns `true` if both `OpenQASM` types map to the same Q# type without errors.
fn maps_to_same_qsharp_type(
a: &qsc_openqasm_parser::semantic::types::Type,
b: &qsc_openqasm_parser::semantic::types::Type,
) -> bool {
let mut errs = Vec::new();
let ty_a = Self::semantic_type_for_qsharp_type(a, Span::default(), &mut errs);
let ty_b = Self::semantic_type_for_qsharp_type(b, Span::default(), &mut errs);
errs.is_empty() && ty_a == ty_b
}

fn get_argument_validation_stmts(
args: &[(&String, qsast::Ty, Span, &Type)],
) -> Vec<qsast::Stmt> {
Expand Down Expand Up @@ -2648,3 +2685,16 @@ impl QasmCompiler {
Some(body)
}
}

/// Follows `ExprKind::Paren` chains, returning the innermost expression.
fn unwrap_parens(expr: &semast::Expr) -> &semast::Expr {
let mut current = expr;
while let semast::ExprKind::Paren(inner) = current.kind.as_ref() {
current = inner;
}
current
}

fn unsupported_err<S: AsRef<str>>(message: S, span: Span) -> CompilerErrorKind {
CompilerErrorKind::NotSupported(message.as_ref().to_string(), span)
}
1 change: 1 addition & 0 deletions source/compiler/qsc_openqasm_compiler/src/tests/expression.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,4 +24,5 @@ mod implicit_cast_from_complex;
mod implicit_cast_from_float;
mod implicit_cast_from_int;
mod indexed;
mod roundtrip_cast;
mod unary;
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