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suboptimal_flops lint for multiply and subtract

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This commit is contained in:
Elliot Bobrow 2022-10-02 21:00:51 -07:00
parent 64243c6f99
commit 7747032b77
7 changed files with 81 additions and 25 deletions
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48
clippy_lints/src/floating_point_arithmetic.rs
View file

@ -311,7 +311,8 @@ fn check_powi(cx: &LateContext<'_>, expr: &Expr<'_>, receiver: &Expr<'_>, args:
if let ExprKind::Binary(
Spanned {
node: BinOpKind::Add, ..
node: op @ (BinOpKind::Add | BinOpKind::Sub),
..
},
lhs,
rhs,
@ -319,6 +320,16 @@ fn check_powi(cx: &LateContext<'_>, expr: &Expr<'_>, receiver: &Expr<'_>, args:
{
let other_addend = if lhs.hir_id == expr.hir_id { rhs } else { lhs };
// Negate expr if original code has subtraction and expr is on the right side
let maybe_neg_sugg = |expr, hir_id| {
let sugg = Sugg::hir(cx, expr, "..");
if matches!(op, BinOpKind::Sub) && hir_id == rhs.hir_id {
format!("-{sugg}")
} else {
sugg.to_string()
}
};
span_lint_and_sugg(
cx,
SUBOPTIMAL_FLOPS,
@ -328,8 +339,8 @@ fn check_powi(cx: &LateContext<'_>, expr: &Expr<'_>, receiver: &Expr<'_>, args:
format!(
"{}.mul_add({}, {})",
Sugg::hir(cx, receiver, "..").maybe_par(),
Sugg::hir(cx, receiver, ".."),
Sugg::hir(cx, other_addend, ".."),
maybe_neg_sugg(receiver, expr.hir_id),
maybe_neg_sugg(other_addend, other_addend.hir_id),
),
Applicability::MachineApplicable,
);
@ -443,7 +454,8 @@ fn is_float_mul_expr<'a>(cx: &LateContext<'_>, expr: &'a Expr<'a>) -> Option<(&'
fn check_mul_add(cx: &LateContext<'_>, expr: &Expr<'_>) {
if let ExprKind::Binary(
Spanned {
node: BinOpKind::Add, ..
node: op @ (BinOpKind::Add | BinOpKind::Sub),
..
},
lhs,
rhs,
@ -457,10 +469,27 @@ fn check_mul_add(cx: &LateContext<'_>, expr: &Expr<'_>) {
}
}
let maybe_neg_sugg = |expr| {
let sugg = Sugg::hir(cx, expr, "..");
if let BinOpKind::Sub = op {
format!("-{sugg}")
} else {
sugg.to_string()
}
};
let (recv, arg1, arg2) = if let Some((inner_lhs, inner_rhs)) = is_float_mul_expr(cx, lhs) {
(inner_lhs, inner_rhs, rhs)
(
inner_lhs,
Sugg::hir(cx, inner_rhs, "..").to_string(),
maybe_neg_sugg(rhs),
)
} else if let Some((inner_lhs, inner_rhs)) = is_float_mul_expr(cx, rhs) {
(inner_lhs, inner_rhs, lhs)
(
inner_lhs,
maybe_neg_sugg(inner_rhs),
Sugg::hir(cx, lhs, "..").to_string(),
)
} else {
return;
};
@ -471,12 +500,7 @@ fn check_mul_add(cx: &LateContext<'_>, expr: &Expr<'_>) {
expr.span,
"multiply and add expressions can be calculated more efficiently and accurately",
"consider using",
format!(
"{}.mul_add({}, {})",
prepare_receiver_sugg(cx, recv),
Sugg::hir(cx, arg1, ".."),
Sugg::hir(cx, arg2, ".."),
),
format!("{}.mul_add({arg1}, {arg2})", prepare_receiver_sugg(cx, recv)),
Applicability::MachineApplicable,
);
}