diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/intrinsics.rs | 12 | ||||
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/operator.rs | 18 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/mir/interpret/error.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/const_prop.rs | 11 |
4 files changed, 30 insertions, 17 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs index d6f856a6f0a..bf7e811c76f 100644 --- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs +++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs @@ -500,15 +500,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { // `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`. // First, check x % y != 0 (or if that computation overflows). let (res, overflow, _ty) = self.overflowing_binary_op(BinOp::Rem, &a, &b)?; - if overflow || res.assert_bits(a.layout.size) != 0 { - // Then, check if `b` is -1, which is the "MIN / -1" case. - let minus1 = Scalar::from_int(-1, dest.layout.size); - let b_scalar = b.to_scalar().unwrap(); - if b_scalar == minus1 { - throw_ub_format!("exact_div: result of dividing MIN by -1 cannot be represented") - } else { - throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b,) - } + assert!(!overflow); // All overflow is UB, so this should never return on overflow. + if res.assert_bits(a.layout.size) != 0 { + throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b) } // `Rem` says this is all right, so we can let `Div` do its job. self.binop_ignore_overflow(BinOp::Div, &a, &b, dest) diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs index 48c90e1881a..079ce9f07b8 100644 --- a/compiler/rustc_const_eval/src/interpret/operator.rs +++ b/compiler/rustc_const_eval/src/interpret/operator.rs @@ -196,16 +196,20 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { _ => None, }; if let Some(op) = op { + let l = self.sign_extend(l, left_layout) as i128; let r = self.sign_extend(r, right_layout) as i128; - // We need a special check for overflowing remainder: - // "int_min % -1" overflows and returns 0, but after casting things to a larger int - // type it does *not* overflow nor give an unrepresentable result! - if bin_op == Rem { - if r == -1 && l == (1 << (size.bits() - 1)) { - return Ok((Scalar::from_int(0, size), true, left_layout.ty)); + + // We need a special check for overflowing Rem and Div since they are *UB* + // on overflow, which can happen with "int_min $OP -1". + if matches!(bin_op, Rem | Div) { + if l == size.signed_int_min() && r == -1 { + if bin_op == Rem { + throw_ub!(RemainderOverflow) + } else { + throw_ub!(DivisionOverflow) + } } } - let l = self.sign_extend(l, left_layout) as i128; let (result, oflo) = op(l, r); // This may be out-of-bounds for the result type, so we have to truncate ourselves. diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs index 98cb90296a5..e524625f966 100644 --- a/compiler/rustc_middle/src/mir/interpret/error.rs +++ b/compiler/rustc_middle/src/mir/interpret/error.rs @@ -233,6 +233,10 @@ pub enum UndefinedBehaviorInfo<'tcx> { DivisionByZero, /// Something was "remainded" by 0 (x % 0). RemainderByZero, + /// Signed division overflowed (INT_MIN / -1). + DivisionOverflow, + /// Signed remainder overflowed (INT_MIN % -1). + RemainderOverflow, /// Overflowing inbounds pointer arithmetic. PointerArithOverflow, /// Invalid metadata in a wide pointer (using `str` to avoid allocations). @@ -310,6 +314,8 @@ impl fmt::Display for UndefinedBehaviorInfo<'_> { } DivisionByZero => write!(f, "dividing by zero"), RemainderByZero => write!(f, "calculating the remainder with a divisor of zero"), + DivisionOverflow => write!(f, "overflow in signed division (dividing MIN by -1)"), + RemainderOverflow => write!(f, "overflow in signed remainder (dividing MIN by -1)"), PointerArithOverflow => write!(f, "overflowing in-bounds pointer arithmetic"), InvalidMeta(msg) => write!(f, "invalid metadata in wide pointer: {}", msg), InvalidVtableDropFn(sig) => write!( diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs index c5ef1e10146..d849bc408fa 100644 --- a/compiler/rustc_mir_transform/src/const_prop.rs +++ b/compiler/rustc_mir_transform/src/const_prop.rs @@ -1196,12 +1196,21 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> { AssertKind::RemainderByZero(op) => { Some(AssertKind::RemainderByZero(eval_to_int(op))) } + AssertKind::Overflow(bin_op @ (BinOp::Div | BinOp::Rem), op1, op2) => { + // Division overflow is *UB* in the MIR, and different than the + // other overflow checks. + Some(AssertKind::Overflow( + *bin_op, + eval_to_int(op1), + eval_to_int(op2), + )) + } AssertKind::BoundsCheck { ref len, ref index } => { let len = eval_to_int(len); let index = eval_to_int(index); Some(AssertKind::BoundsCheck { len, index }) } - // Overflow is are already covered by checks on the binary operators. + // Remaining overflow errors are already covered by checks on the binary operators. AssertKind::Overflow(..) | AssertKind::OverflowNeg(_) => None, // Need proper const propagator for these. _ => None, |