bjoernager/rust
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Make overflow handling more precise

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This commit is contained in:
Jannis Christopher Köhl 2022-10-15 23:40:03 +02:00
parent be9013f02b
commit 931d99f61f
1 changed files with 18 additions and 11 deletions
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29
compiler/rustc_mir_transform/src/dataflow_const_prop.rs
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@ -73,16 +73,26 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'tcx> {
}); });
if value_target.is_some() || overflow_target.is_some() { if value_target.is_some() || overflow_target.is_some() {
let (val, mut overflow) = self.binary_op(state, *op, left, right); let (val, overflow) = self.binary_op(state, *op, left, right);
if !self.propagate_overflow {
overflow = FlatSet::Top;
}
if let Some(value_target) = value_target { if let Some(value_target) = value_target {
state.assign_idx(value_target, ValueOrPlaceOrRef::Value(val), self.map()); state.assign_idx(value_target, ValueOrPlaceOrRef::Value(val), self.map());
} }
if let Some(overflow_target) = overflow_target { if let Some(overflow_target) = overflow_target {
let overflow = match overflow {
FlatSet::Top => FlatSet::Top,
FlatSet::Elem(overflow) => {
if overflow && !self.propagate_overflow {
FlatSet::Top
} else {
self.wrap_scalar(
Scalar::from_bool(overflow),
self.tcx.types.bool,
)
}
}
FlatSet::Bottom => FlatSet::Bottom,
};
state.assign_idx( state.assign_idx(
overflow_target, overflow_target,
ValueOrPlaceOrRef::Value(overflow), ValueOrPlaceOrRef::Value(overflow),
@ -120,8 +130,8 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'tcx> {
} }
} }
Rvalue::BinaryOp(op, box (left, right)) => { Rvalue::BinaryOp(op, box (left, right)) => {
// Overflows must be ignored here.
let (val, _overflow) = self.binary_op(state, *op, left, right); let (val, _overflow) = self.binary_op(state, *op, left, right);
// FIXME: Just ignore overflow here?
ValueOrPlaceOrRef::Value(val) ValueOrPlaceOrRef::Value(val)
} }
Rvalue::UnaryOp(op, operand) => match self.eval_operand(operand, state) { Rvalue::UnaryOp(op, operand) => match self.eval_operand(operand, state) {
@ -230,16 +240,13 @@ impl<'tcx> ConstAnalysis<'tcx> {
op: BinOp, op: BinOp,
left: &Operand<'tcx>, left: &Operand<'tcx>,
right: &Operand<'tcx>, right: &Operand<'tcx>,
) -> (FlatSet<ScalarTy<'tcx>>, FlatSet<ScalarTy<'tcx>>) { ) -> (FlatSet<ScalarTy<'tcx>>, FlatSet<bool>) {
let left = self.eval_operand(left, state); let left = self.eval_operand(left, state);
let right = self.eval_operand(right, state); let right = self.eval_operand(right, state);
match (left, right) { match (left, right) {
(FlatSet::Elem(left), FlatSet::Elem(right)) => { (FlatSet::Elem(left), FlatSet::Elem(right)) => {
match self.ecx.overflowing_binary_op(op, &left, &right) { match self.ecx.overflowing_binary_op(op, &left, &right) {
Ok((val, overflow, ty)) => ( Ok((val, overflow, ty)) => (self.wrap_scalar(val, ty), FlatSet::Elem(overflow)),
self.wrap_scalar(val, ty),
self.wrap_scalar(Scalar::from_bool(overflow), self.tcx.types.bool),
),
_ => (FlatSet::Top, FlatSet::Top), _ => (FlatSet::Top, FlatSet::Top),
} }
} }