diff options
| -rw-r--r-- | library/core/src/option.rs | 24 | ||||
| -rw-r--r-- | tests/codegen/option-as-slice.rs | 35 |
2 files changed, 51 insertions, 8 deletions
diff --git a/library/core/src/option.rs b/library/core/src/option.rs index 8ec7716012f..1a8fe1e6051 100644 --- a/library/core/src/option.rs +++ b/library/core/src/option.rs @@ -770,6 +770,13 @@ impl<T> Option<T> { } } + #[inline] + const fn len(&self) -> usize { + // Using the intrinsic avoids emitting a branch to get the 0 or 1. + let discriminant: isize = crate::intrinsics::discriminant_value(self); + discriminant as usize + } + /// Returns a slice of the contained value, if any. If this is `None`, an /// empty slice is returned. This can be useful to have a single type of /// iterator over an `Option` or slice. @@ -812,7 +819,7 @@ impl<T> Option<T> { unsafe { slice::from_raw_parts( (self as *const Self).byte_add(core::mem::offset_of!(Self, Some.0)).cast(), - self.is_some() as usize, + self.len(), ) } } @@ -869,7 +876,7 @@ impl<T> Option<T> { unsafe { slice::from_raw_parts_mut( (self as *mut Self).byte_add(core::mem::offset_of!(Self, Some.0)).cast(), - self.is_some() as usize, + self.len(), ) } } @@ -2242,10 +2249,8 @@ impl<A> Iterator for Item<A> { #[inline] fn size_hint(&self) -> (usize, Option<usize>) { - match self.opt { - Some(_) => (1, Some(1)), - None => (0, Some(0)), - } + let len = self.len(); + (len, Some(len)) } } @@ -2256,7 +2261,12 @@ impl<A> DoubleEndedIterator for Item<A> { } } -impl<A> ExactSizeIterator for Item<A> {} +impl<A> ExactSizeIterator for Item<A> { + #[inline] + fn len(&self) -> usize { + self.opt.len() + } +} impl<A> FusedIterator for Item<A> {} unsafe impl<A> TrustedLen for Item<A> {} diff --git a/tests/codegen/option-as-slice.rs b/tests/codegen/option-as-slice.rs index 65637a2495d..cfa479aa4b2 100644 --- a/tests/codegen/option-as-slice.rs +++ b/tests/codegen/option-as-slice.rs @@ -14,6 +14,14 @@ pub fn u64_opt_as_slice(o: &Option<u64>) -> &[u64] { // CHECK-NOT: br // CHECK-NOT: switch // CHECK-NOT: icmp + // CHECK: %[[LEN:.+]] = load i64,{{.+}} !range ![[META_U64:.+]], !noundef + // CHECK-NOT: select + // CHECK-NOT: br + // CHECK-NOT: switch + // CHECK-NOT: icmp + // CHECK: %[[T0:.+]] = insertvalue { ptr, i64 } poison, ptr %{{.+}}, 0 + // CHECK-NEXT: %[[T1:.+]] = insertvalue { ptr, i64 } %[[T0]], i64 %[[LEN]], 1 + // CHECK-NEXT: ret { ptr, i64 } %[[T1]] o.as_slice() } @@ -25,10 +33,35 @@ pub fn nonzero_u64_opt_as_slice(o: &Option<NonZero<u64>>) -> &[NonZero<u64>] { // CHECK-NOT: switch // CHECK-NOT: icmp // CHECK: %[[NZ:.+]] = icmp ne i64 %{{.+}}, 0 - // CHECK-NEXT: zext i1 %[[NZ]] to i64 + // CHECK-NEXT: %[[LEN:.+]] = zext i1 %[[NZ]] to i64 // CHECK-NOT: select // CHECK-NOT: br // CHECK-NOT: switch // CHECK-NOT: icmp + // CHECK: %[[T0:.+]] = insertvalue { ptr, i64 } poison, ptr %o, 0 + // CHECK-NEXT: %[[T1:.+]] = insertvalue { ptr, i64 } %[[T0]], i64 %[[LEN]], 1 + // CHECK-NEXT: ret { ptr, i64 } %[[T1]] o.as_slice() } + +// CHECK-LABEL: @u8_opt_as_slice +#[no_mangle] +pub fn u8_opt_as_slice(o: &Option<u8>) -> &[u8] { + // CHECK-NOT: select + // CHECK-NOT: br + // CHECK-NOT: switch + // CHECK-NOT: icmp + // CHECK: %[[TAG:.+]] = load i8,{{.+}} !range ![[META_U8:.+]], !noundef + // CHECK: %[[LEN:.+]] = zext{{.*}} i8 %[[TAG]] to i64 + // CHECK-NOT: select + // CHECK-NOT: br + // CHECK-NOT: switch + // CHECK-NOT: icmp + // CHECK: %[[T0:.+]] = insertvalue { ptr, i64 } poison, ptr %{{.+}}, 0 + // CHECK-NEXT: %[[T1:.+]] = insertvalue { ptr, i64 } %[[T0]], i64 %[[LEN]], 1 + // CHECK-NEXT: ret { ptr, i64 } %[[T1]] + o.as_slice() +} + +// CHECK: ![[META_U64]] = !{i64 0, i64 2} +// CHECK: ![[META_U8]] = !{i8 0, i8 2} |