Auto merge of #69614 - estebank:ice-age, r=davidtwco

[rust.git] / src / librustc_mir / interpret / operator.rs

diff --git a/src/librustc_mir/interpret/operator.rs b/src/librustc_mir/interpret/operator.rs
index abe437bd8d7c66f62ebac7d9b7b6df052f3b9787..f2ee5e047a88e5b3366f93dcbcd2cec366c094d2 100644 (file)
--- a/src/librustc_mir/interpret/operator.rs
+++ b/src/librustc_mir/interpret/operator.rs
@@ -6,7 +6,7 @@
     Ty,
 };
 use rustc_apfloat::Float;
-use syntax::ast::FloatTy;
+use rustc_ast::ast::FloatTy;
 
 use super::{ImmTy, Immediate, InterpCx, Machine, PlaceTy};
 
@@ -234,7 +234,7 @@ fn binary_int_op(
             BitXor => (Scalar::from_uint(l ^ r, size), left_layout.ty),
 
             Add | Sub | Mul | Rem | Div => {
-                debug_assert!(!left_layout.abi.is_signed());
+                assert!(!left_layout.abi.is_signed());
                 let op: fn(u128, u128) -> (u128, bool) = match bin_op {
                     Add => u128::overflowing_add,
                     Sub => u128::overflowing_sub,
@@ -342,7 +342,7 @@ pub fn overflowing_binary_op(
         }
     }
 
-    /// Typed version of `checked_binary_op`, returning an `ImmTy`. Also ignores overflows.
+    /// Typed version of `overflowing_binary_op`, returning an `ImmTy`. Also ignores overflows.
     #[inline]
     pub fn binary_op(
         &self,
@@ -354,11 +354,13 @@ pub fn binary_op(
         Ok(ImmTy::from_scalar(val, self.layout_of(ty)?))
     }
 
-    pub fn unary_op(
+    /// Returns the result of the specified operation, whether it overflowed, and
+    /// the result type.
+    pub fn overflowing_unary_op(
         &self,
         un_op: mir::UnOp,
         val: ImmTy<'tcx, M::PointerTag>,
-    ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
+    ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
         use rustc::mir::UnOp::*;
 
         let layout = val.layout;
@@ -372,7 +374,7 @@ pub fn unary_op(
                     Not => !val,
                     _ => bug!("Invalid bool op {:?}", un_op),
                 };
-                Ok(ImmTy::from_scalar(Scalar::from_bool(res), self.layout_of(self.tcx.types.bool)?))
+                Ok((Scalar::from_bool(res), false, self.tcx.types.bool))
             }
             ty::Float(fty) => {
                 let res = match (un_op, fty) {
@@ -380,21 +382,36 @@ pub fn unary_op(
                     (Neg, FloatTy::F64) => Scalar::from_f64(-val.to_f64()?),
                     _ => bug!("Invalid float op {:?}", un_op),
                 };
-                Ok(ImmTy::from_scalar(res, layout))
+                Ok((res, false, layout.ty))
             }
             _ => {
                 assert!(layout.ty.is_integral());
                 let val = self.force_bits(val, layout.size)?;
-                let res = match un_op {
-                    Not => !val,
+                let (res, overflow) = match un_op {
+                    Not => (self.truncate(!val, layout), false), // bitwise negation, then truncate
                     Neg => {
+                        // arithmetic negation
                         assert!(layout.abi.is_signed());
-                        (-(val as i128)) as u128
+                        let val = self.sign_extend(val, layout) as i128;
+                        let (res, overflow) = val.overflowing_neg();
+                        let res = res as u128;
+                        // Truncate to target type.
+                        // If that truncation loses any information, we have an overflow.
+                        let truncated = self.truncate(res, layout);
+                        (truncated, overflow || self.sign_extend(truncated, layout) != res)
                     }
                 };
-                // res needs tuncating
-                Ok(ImmTy::from_uint(self.truncate(res, layout), layout))
+                Ok((Scalar::from_uint(res, layout.size), overflow, layout.ty))
             }
         }
     }
+
+    pub fn unary_op(
+        &self,
+        un_op: mir::UnOp,
+        val: ImmTy<'tcx, M::PointerTag>,
+    ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
+        let (val, _overflow, ty) = self.overflowing_unary_op(un_op, val)?;
+        Ok(ImmTy::from_scalar(val, self.layout_of(ty)?))
+    }
 }