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Improvement on divide before multiply detector #156

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Aug 14, 2023
Merged

Improvement on divide before multiply detector #156

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94d4e3c
Improvement on divide before multiply detector
arlosiggio Aug 9, 2023
6f2920f
Run cargo-fmt on missing files
aon Aug 14, 2023
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76 changes: 29 additions & 47 deletions detectors/divide-before-multiply/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -38,68 +38,50 @@ dylint_linting::declare_late_lint! {
"Division should be performed after multiplication"
}

impl<'tcx> LateLintPass<'tcx> for DivideBeforeMultiply {
fn check_fn(
&mut self,
cx: &LateContext<'tcx>,
_: rustc_hir::intravisit::FnKind<'tcx>,
_: &'tcx rustc_hir::FnDecl<'tcx>,
body: &'tcx rustc_hir::Body<'tcx>,
_: Span,
_: rustc_hir::HirId,
) {
struct DivideBeforeMultiplyVisitor {
has_multiplication: bool,
is_precision_loss: bool,
is_precision_loss_span: Vec<Option<Span>>,
}
fn get_divisions_inside_expr<'tcx>(expr: &'tcx Expr<'_>) -> Vec<Span> {
struct DivisionsInsideExpr {
divisions: Vec<Span>,
}

impl<'tcx> Visitor<'tcx> for DivideBeforeMultiplyVisitor {
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
if_chain! {
if let ExprKind::Binary(binop, _, _) = expr.kind;
if let BinOpKind::Mul = binop.node;
then {
self.has_multiplication = true;
walk_expr(self, expr);
}
impl<'tcx> Visitor<'tcx> for DivisionsInsideExpr {
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
if_chain! {
if let ExprKind::Binary(op, _lexpr, _rexpr) = expr.kind;
if BinOpKind::Div == op.node;
then{
self.divisions.push(expr.span);
}

if_chain!(
if self.has_multiplication;
if let ExprKind::Binary(binop, _, _) = expr.kind;
if let BinOpKind::Div = binop.node;
then {
self.is_precision_loss = true;
self.is_precision_loss_span.push(Some(expr.span));
}
);

walk_expr(self, expr);
}
walk_expr(self, expr);
}
}

let mut visitor = DivisionsInsideExpr {
divisions: Vec::default(),
};

let mut visitor = DivideBeforeMultiplyVisitor {
has_multiplication: false,
is_precision_loss: false,
is_precision_loss_span: Vec::new(),
};
walk_expr(&mut visitor, expr);

walk_expr(&mut visitor, body.value);
return visitor.divisions;
}

if visitor.is_precision_loss {
visitor.is_precision_loss_span.iter().for_each(|span| {
if let Some(span) = span {
impl<'tcx> LateLintPass<'tcx> for DivideBeforeMultiply {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx rustc_hir::Expr<'tcx>) {
if_chain! {
if let ExprKind::Binary(op, _lexpr, _rexpr) = expr.kind;
if BinOpKind::Mul == op.node;
then{
for division in get_divisions_inside_expr(expr) {
span_lint_and_help(
cx,
DIVIDE_BEFORE_MULTIPLY,
*span,
division,
"Division before multiplication might result in a loss of precision",
None,
"Consider reversing the order of operations to reduce the loss of precision.",
);
}
});
}
}
}
}
Expand Down
17 changes: 9 additions & 8 deletions detectors/unprotected-mapping-operation/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,9 @@ extern crate rustc_hir;
extern crate rustc_middle;
extern crate rustc_span;

use clippy_utils::diagnostics::span_lint;
use std::collections::HashSet;

use clippy_utils::diagnostics::span_lint;
use rustc_hir::QPath;
use rustc_hir::{
intravisit::{walk_expr, Visitor},
Expand Down Expand Up @@ -148,7 +149,7 @@ impl<'tcx> LateLintPass<'tcx> for UnprotectedMappingOperation {
&caller_and_map_ops,
false,
&mut vec![],
&mut HashSet::<BasicBlock>::default()
&mut HashSet::<BasicBlock>::default(),
);
for place in unchecked_places {
span_lint(
Expand Down Expand Up @@ -229,7 +230,7 @@ impl<'tcx> LateLintPass<'tcx> for UnprotectedMappingOperation {
caller_and_map_ops,
comparison_with_caller,
tainted_places,
visited_bbs
visited_bbs,
));
}
return ret_vec;
Expand Down Expand Up @@ -277,7 +278,7 @@ impl<'tcx> LateLintPass<'tcx> for UnprotectedMappingOperation {
caller_and_map_ops,
after_comparison,
tainted_places,
visited_bbs
visited_bbs,
));
}
}
Expand All @@ -290,7 +291,7 @@ impl<'tcx> LateLintPass<'tcx> for UnprotectedMappingOperation {
caller_and_map_ops,
after_comparison,
tainted_places,
visited_bbs
visited_bbs,
));
}
TerminatorKind::Yield { resume, .. } => {
Expand All @@ -300,7 +301,7 @@ impl<'tcx> LateLintPass<'tcx> for UnprotectedMappingOperation {
caller_and_map_ops,
after_comparison,
tainted_places,
visited_bbs
visited_bbs,
));
}
TerminatorKind::FalseEdge { real_target, .. }
Expand All @@ -311,7 +312,7 @@ impl<'tcx> LateLintPass<'tcx> for UnprotectedMappingOperation {
caller_and_map_ops,
after_comparison,
tainted_places,
visited_bbs
visited_bbs,
));
}
TerminatorKind::InlineAsm { destination, .. } => {
Expand All @@ -322,7 +323,7 @@ impl<'tcx> LateLintPass<'tcx> for UnprotectedMappingOperation {
caller_and_map_ops,
after_comparison,
tainted_places,
visited_bbs
visited_bbs,
));
}
}
Expand Down