From c67fc2e4c5cf062725458108042dd89d618bd8de Mon Sep 17 00:00:00 2001
From: miguel raz <miguelraz@gmail.com>
Date: Mon, 25 Jan 2021 17:58:29 -0600
Subject: [PATCH] Add guards/tests for div,rem overflow cases

---
 crates/core_simd/src/ops.rs                   | 29 +++++++++-
 crates/core_simd/tests/ops_impl/int_macros.rs | 57 +++++++++++++++++++
 2 files changed, 84 insertions(+), 2 deletions(-)

diff --git a/crates/core_simd/src/ops.rs b/crates/core_simd/src/ops.rs
index a21e9ab5bf1..51e97757c54 100644
--- a/crates/core_simd/src/ops.rs
+++ b/crates/core_simd/src/ops.rs
@@ -283,13 +283,20 @@ macro_rules! impl_unsigned_int_ops {
 
                         #[inline]
                         fn div(self, rhs: Self) -> Self::Output {
-                            // TODO there is probably a better way of doing this
-                            if AsRef::<[$scalar]>::as_ref(&rhs)
+                            if rhs.as_slice()
                                 .iter()
                                 .any(|x| *x == 0)
                             {
                                 panic!("attempt to divide by zero");
                             }
+
+                            // Guards for div(MIN, -1),
+                            // this check only applies to signed ints
+                            if <$scalar>::MIN != 0 && self.as_slice().iter()
+                                    .zip(rhs.as_slice().iter())
+                                    .any(|(x,y)| *x == <$scalar>::MIN && *y == -1 as _) {
+                                panic!("attempt to divide with overflow");
+                            }
                             unsafe { crate::intrinsics::simd_div(self, rhs) }
                         }
                     }
@@ -304,6 +311,11 @@ macro_rules! impl_unsigned_int_ops {
                             if rhs == 0 {
                                 panic!("attempt to divide by zero");
                             }
+                            if <$scalar>::MIN != 0 &&
+                                self.as_slice().iter().any(|x| *x == <$scalar>::MIN) &&
+                                rhs == -1 as _ {
+                                    panic!("attempt to divide with overflow");
+                            }
                             let rhs = Self::splat(rhs);
                             unsafe { crate::intrinsics::simd_div(self, rhs) }
                         }
@@ -353,6 +365,14 @@ macro_rules! impl_unsigned_int_ops {
                             {
                                 panic!("attempt to calculate the remainder with a divisor of zero");
                             }
+
+                            // Guards for rem(MIN, -1)
+                            // this branch applies the check only to signed ints
+                            if <$scalar>::MIN != 0 && self.as_slice().iter()
+                                    .zip(rhs.as_slice().iter())
+                                    .any(|(x,y)| *x == <$scalar>::MIN && *y == -1 as _) {
+                                panic!("attempt to calculate the remainder with overflow");
+                            }
                             unsafe { crate::intrinsics::simd_rem(self, rhs) }
                         }
                     }
@@ -367,6 +387,11 @@ macro_rules! impl_unsigned_int_ops {
                             if rhs == 0 {
                                 panic!("attempt to calculate the remainder with a divisor of zero");
                             }
+                            if <$scalar>::MIN != 0 &&
+                                self.as_slice().iter().any(|x| *x == <$scalar>::MIN) &&
+                                rhs == -1 as _ {
+                                    panic!("attempt to calculate the remainder with overflow");
+                            }
                             let rhs = Self::splat(rhs);
                             unsafe { crate::intrinsics::simd_rem(self, rhs) }
                         }
diff --git a/crates/core_simd/tests/ops_impl/int_macros.rs b/crates/core_simd/tests/ops_impl/int_macros.rs
index af956aa3e52..43c75c6a9c4 100644
--- a/crates/core_simd/tests/ops_impl/int_macros.rs
+++ b/crates/core_simd/tests/ops_impl/int_macros.rs
@@ -228,6 +228,39 @@ macro_rules! int_tests {
                 assert_biteq!(a, expected);
             }
 
+            #[test]
+            #[should_panic]
+            fn div_min_panics() {
+                let a = from_slice(&vec![$scalar::MIN; 64]);
+                let b = from_slice(&vec![-1; 64]);
+                let _ = a / b;
+            }
+
+            #[test]
+            #[should_panic]
+            fn div_by_all_zeros_panics() {
+                let a = from_slice(&A);
+                let b = from_slice(&vec![0 ; 64]);
+                let _ = a / b;
+            }
+
+            #[test]
+            #[should_panic]
+            fn div_by_one_zero_panics() {
+                let a = from_slice(&A);
+                let mut b = from_slice(&B);
+                b[0] = 0 as _;
+                let _ = a / b;
+            }
+
+            #[test]
+            #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
+            fn div_min_neg_one_no_panic() {
+                let a = from_slice(&A);
+                let b = from_slice(&vec![-1; 64]);
+                let _ = a / b;
+            }
+
             #[test]
             #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
             fn rem() {
@@ -275,6 +308,30 @@ macro_rules! int_tests {
                 assert_biteq!(a, expected);
             }
 
+            #[test]
+            #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
+            fn rem_min_neg_one_no_panic() {
+                let a = from_slice(&A);
+                let b = from_slice(&vec![-1; 64]);
+                let _ = a % b;
+            }
+
+            #[test]
+            #[should_panic]
+            fn rem_min_panic() {
+                let a = from_slice(&vec![$scalar::MIN; 64]);
+                let b = from_slice(&vec![-1 ; 64]);
+                let _ = a % b;
+            }
+
+            #[test]
+            #[should_panic]
+            fn rem_min_zero_panic() {
+                let a = from_slice(&A);
+                let b = from_slice(&vec![0 ; 64]);
+                let _ = a % b;
+            }
+
             #[test]
             #[cfg_attr(target_arch = "wasm32", wasm_bindgen_test)]
             fn bitand() {