Asserts the maximum value that can be returned from Vec::len
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EFanZh
parent
4790a435cb
commit
b5ea631fbd
4 changed files with 72 additions and 2 deletions
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@ -56,7 +56,6 @@
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#[cfg(not(no_global_oom_handling))]
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use core::cmp;
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use core::cmp::Ordering;
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use core::fmt;
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use core::hash::{Hash, Hasher};
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#[cfg(not(no_global_oom_handling))]
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use core::iter;
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@ -65,6 +64,7 @@ use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
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use core::ops::{self, Index, IndexMut, Range, RangeBounds};
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use core::ptr::{self, NonNull};
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use core::slice::{self, SliceIndex};
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use core::{fmt, intrinsics};
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#[unstable(feature = "extract_if", reason = "recently added", issue = "43244")]
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pub use self::extract_if::ExtractIf;
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@ -2675,7 +2675,14 @@ impl<T, A: Allocator> Vec<T, A> {
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#[rustc_const_unstable(feature = "const_vec_string_slice", issue = "129041")]
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#[rustc_confusables("length", "size")]
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pub const fn len(&self) -> usize {
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self.len
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let len = self.len;
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// SAFETY: The maximum capacity of `Vec<T>` is `isize::MAX` bytes, so the maximum value can
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// be returned is `usize::checked_div(mem::size_of::<T>()).unwrap_or(usize::MAX)`, which
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// matches the definition of `T::MAX_SLICE_LEN`.
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unsafe { intrinsics::assume(len <= T::MAX_SLICE_LEN) };
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len
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}
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/// Returns `true` if the vector contains no elements.
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@ -1241,6 +1241,17 @@ pub trait SizedTypeProperties: Sized {
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#[doc(hidden)]
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#[unstable(feature = "sized_type_properties", issue = "none")]
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const LAYOUT: Layout = Layout::new::<Self>();
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/// The largest safe length for a `[Self]`.
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///
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/// Anything larger than this would make `size_of_val` overflow `isize::MAX`,
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/// which is never allowed for a single object.
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#[doc(hidden)]
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#[unstable(feature = "sized_type_properties", issue = "none")]
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const MAX_SLICE_LEN: usize = match size_of::<Self>() {
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0 => usize::MAX,
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n => (isize::MAX as usize) / n,
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};
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}
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#[doc(hidden)]
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#[unstable(feature = "sized_type_properties", issue = "none")]
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@ -36,6 +36,9 @@ pub struct Baz {
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// CHECK-LABEL: @vec_iterator_cast_primitive
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#[no_mangle]
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pub fn vec_iterator_cast_primitive(vec: Vec<i8>) -> Vec<u8> {
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// CHECK-NOT: loop
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: loop
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// CHECK-NOT: call
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vec.into_iter().map(|e| e as u8).collect()
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@ -44,14 +47,37 @@ pub fn vec_iterator_cast_primitive(vec: Vec<i8>) -> Vec<u8> {
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// CHECK-LABEL: @vec_iterator_cast_wrapper
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#[no_mangle]
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pub fn vec_iterator_cast_wrapper(vec: Vec<u8>) -> Vec<Wrapper<u8>> {
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// CHECK-NOT: loop
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: loop
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// CHECK-NOT: call
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vec.into_iter().map(|e| Wrapper(e)).collect()
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}
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// CHECK-LABEL: @vec_iterator_cast_signed
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#[no_mangle]
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pub fn vec_iterator_cast_signed(vec: Vec<i32>) -> Vec<u32> {
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// CHECK-NOT: and i{{[0-9]+}} %{{.*}}, {{[0-9]+}}
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vec.into_iter().map(|e| u32::from_ne_bytes(e.to_ne_bytes())).collect()
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}
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// CHECK-LABEL: @vec_iterator_cast_signed_nested
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#[no_mangle]
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pub fn vec_iterator_cast_signed_nested(vec: Vec<Vec<i32>>) -> Vec<Vec<u32>> {
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// CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
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// CHECK-NOT: %{{.*}} = udiv
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vec.into_iter()
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.map(|e| e.into_iter().map(|e| u32::from_ne_bytes(e.to_ne_bytes())).collect())
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.collect()
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}
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// CHECK-LABEL: @vec_iterator_cast_unwrap
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#[no_mangle]
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pub fn vec_iterator_cast_unwrap(vec: Vec<Wrapper<u8>>) -> Vec<u8> {
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// CHECK-NOT: loop
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: loop
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// CHECK-NOT: call
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vec.into_iter().map(|e| e.0).collect()
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@ -60,6 +86,9 @@ pub fn vec_iterator_cast_unwrap(vec: Vec<Wrapper<u8>>) -> Vec<u8> {
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// CHECK-LABEL: @vec_iterator_cast_aggregate
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#[no_mangle]
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pub fn vec_iterator_cast_aggregate(vec: Vec<[u64; 4]>) -> Vec<Foo> {
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// CHECK-NOT: loop
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: loop
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// CHECK-NOT: call
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vec.into_iter().map(|e| unsafe { std::mem::transmute(e) }).collect()
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@ -68,6 +97,9 @@ pub fn vec_iterator_cast_aggregate(vec: Vec<[u64; 4]>) -> Vec<Foo> {
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// CHECK-LABEL: @vec_iterator_cast_deaggregate_tra
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#[no_mangle]
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pub fn vec_iterator_cast_deaggregate_tra(vec: Vec<Bar>) -> Vec<[u64; 4]> {
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// CHECK-NOT: loop
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: loop
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// CHECK-NOT: call
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@ -81,6 +113,9 @@ pub fn vec_iterator_cast_deaggregate_tra(vec: Vec<Bar>) -> Vec<[u64; 4]> {
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// CHECK-LABEL: @vec_iterator_cast_deaggregate_fold
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#[no_mangle]
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pub fn vec_iterator_cast_deaggregate_fold(vec: Vec<Baz>) -> Vec<[u64; 4]> {
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// CHECK-NOT: loop
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: loop
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// CHECK-NOT: call
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@ -94,6 +129,11 @@ pub fn vec_iterator_cast_deaggregate_fold(vec: Vec<Baz>) -> Vec<[u64; 4]> {
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// CHECK-LABEL: @vec_iterator_cast_unwrap_drop
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#[no_mangle]
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pub fn vec_iterator_cast_unwrap_drop(vec: Vec<Wrapper<String>>) -> Vec<String> {
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// CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
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// CHECK-NOT: %{{.*}} = mul
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// CHECK-NOT: %{{.*}} = udiv
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
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// CHECK-NOT: call
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// CHECK-NOT: %{{.*}} = mul
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@ -105,10 +145,16 @@ pub fn vec_iterator_cast_unwrap_drop(vec: Vec<Wrapper<String>>) -> Vec<String> {
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// CHECK-LABEL: @vec_iterator_cast_wrap_drop
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#[no_mangle]
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pub fn vec_iterator_cast_wrap_drop(vec: Vec<String>) -> Vec<Wrapper<String>> {
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// CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
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// CHECK-NOT: %{{.*}} = mul
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// CHECK-NOT: %{{.*}} = udiv
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// CHECK: call
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// CHECK-SAME: void @llvm.assume(i1 %{{.+}})
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// CHECK-NOT: br i1 %{{.*}}, label %{{.*}}, label %{{.*}}
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// CHECK-NOT: call
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// CHECK-NOT: %{{.*}} = mul
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// CHECK-NOT: %{{.*}} = udiv
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// CHECK: ret void
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vec.into_iter().map(Wrapper).collect()
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}
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@ -1,3 +1,6 @@
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//@ revisions: llvm-pre-19 llvm-19
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//@ [llvm-19] min-llvm-version: 19
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//@ [llvm-pre-19] max-llvm-major-version: 18
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//@ compile-flags: -O
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#![crate_type = "lib"]
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@ -9,6 +12,9 @@ pub fn noop(v: &mut Vec<u8>) {
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// CHECK-NOT: call
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// CHECK: tail call void @llvm.assume
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// CHECK-NOT: grow_one
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// llvm-pre-19: call
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// llvm-pre-19-same: void @llvm.assume
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// llvm-pre-19-NOT: grow_one
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// CHECK-NOT: call
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// CHECK: ret
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if let Some(x) = v.pop() {
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