diff --git a/library/core/src/slice/cmp.rs b/library/core/src/slice/cmp.rs index 18073f4afedf7..72af47c71dd64 100644 --- a/library/core/src/slice/cmp.rs +++ b/library/core/src/slice/cmp.rs @@ -75,28 +75,6 @@ where } } -// Use an equal-pointer optimization when types are `Eq` -// We can't make `A` and `B` the same type because `min_specialization` won't -// allow it. -impl SlicePartialEq for [A] -where - A: MarkerEq, -{ - default fn equal(&self, other: &[B]) -> bool { - if self.len() != other.len() { - return false; - } - - // While performance would suffer if `guaranteed_eq` just returned `false` - // for all arguments, correctness and return value of this function are not affected. - if self.as_ptr().guaranteed_eq(other.as_ptr() as *const A) { - return true; - } - - self.iter().zip(other.iter()).all(|(x, y)| x == y) - } -} - // Use memcmp for bytewise equality when the types allow impl SlicePartialEq for [A] where @@ -107,11 +85,6 @@ where return false; } - // While performance would suffer if `guaranteed_eq` just returned `false` - // for all arguments, correctness and return value of this function are not affected. - if self.as_ptr().guaranteed_eq(other.as_ptr() as *const A) { - return true; - } // SAFETY: `self` and `other` are references and are thus guaranteed to be valid. // The two slices have been checked to have the same size above. unsafe { diff --git a/src/test/codegen/slice-ref-equality.rs b/src/test/codegen/slice-ref-equality.rs new file mode 100644 index 0000000000000..acc7879e7b189 --- /dev/null +++ b/src/test/codegen/slice-ref-equality.rs @@ -0,0 +1,16 @@ +// compile-flags: -C opt-level=3 + +#![crate_type = "lib"] + +// #71602: check that slice equality just generates a single bcmp + +// CHECK-LABEL: @is_zero_slice +#[no_mangle] +pub fn is_zero_slice(data: &[u8; 4]) -> bool { + // CHECK: start: + // CHECK-NEXT: %{{.+}} = getelementptr {{.+}} + // CHECK-NEXT: %[[BCMP:.+]] = tail call i32 @{{bcmp|memcmp}}({{.+}}) + // CHECK-NEXT: %[[EQ:.+]] = icmp eq i32 %[[BCMP]], 0 + // CHECK-NEXT: ret i1 %[[EQ]] + *data == [0; 4] +}