diff --git a/library/core/src/slice/index.rs b/library/core/src/slice/index.rs
index 27afd3b8017..373b4aee47a 100644
--- a/library/core/src/slice/index.rs
+++ b/library/core/src/slice/index.rs
@@ -233,7 +233,10 @@ unsafe impl<T> SliceIndex<[T]> for usize {
// cannot be longer than `isize::MAX`. They also guarantee that
// `self` is in bounds of `slice` so `self` cannot overflow an `isize`,
// so the call to `add` is safe.
- unsafe { slice.as_ptr().add(self) }
+ unsafe {
+ crate::intrinsics::assume(self < slice.len());
+ slice.as_ptr().add(self)
+ }
}
#[inline]
diff --git a/src/tools/miri/tests/fail/stacked_borrows/zst_slice.rs b/src/tools/miri/tests/fail/stacked_borrows/zst_slice.rs
index fd51fa6468a..be4dac9957d 100644
--- a/src/tools/miri/tests/fail/stacked_borrows/zst_slice.rs
+++ b/src/tools/miri/tests/fail/stacked_borrows/zst_slice.rs
@@ -1,11 +1,10 @@
//@compile-flags: -Zmiri-strict-provenance
-//@error-in-other-file: /retag .* tag does not exist in the borrow stack/
fn main() {
unsafe {
let a = [1, 2, 3];
let s = &a[0..0];
assert_eq!(s.len(), 0);
- assert_eq!(*s.get_unchecked(1), 2);
+ assert_eq!(*s.as_ptr().add(1), 2); //~ ERROR: /retag .* tag does not exist in the borrow stack/
}
}
diff --git a/src/tools/miri/tests/fail/stacked_borrows/zst_slice.stderr b/src/tools/miri/tests/fail/stacked_borrows/zst_slice.stderr
index 5568051905c..acae479ced2 100644
--- a/src/tools/miri/tests/fail/stacked_borrows/zst_slice.stderr
+++ b/src/tools/miri/tests/fail/stacked_borrows/zst_slice.stderr
@@ -1,26 +1,22 @@
error: Undefined Behavior: trying to retag from <TAG> for SharedReadOnly permission at ALLOC[0x4], but that tag does not exist in the borrow stack for this location
- --> RUSTLIB/core/src/slice/mod.rs:LL:CC
+ --> $DIR/zst_slice.rs:LL:CC
|
-LL | unsafe { &*index.get_unchecked(self) }
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
- | |
- | trying to retag from <TAG> for SharedReadOnly permission at ALLOC[0x4], but that tag does not exist in the borrow stack for this location
- | this error occurs as part of retag at ALLOC[0x4..0x8]
+LL | assert_eq!(*s.as_ptr().add(1), 2);
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | |
+ | trying to retag from <TAG> for SharedReadOnly permission at ALLOC[0x4], but that tag does not exist in the borrow stack for this location
+ | this error occurs as part of retag at ALLOC[0x4..0x8]
|
= help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
= help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
help: <TAG> would have been created here, but this is a zero-size retag ([0x0..0x0]) so the tag in question does not exist anywhere
--> $DIR/zst_slice.rs:LL:CC
|
-LL | assert_eq!(*s.get_unchecked(1), 2);
- | ^^^^^^^^^^^^^^^^^^
+LL | assert_eq!(*s.as_ptr().add(1), 2);
+ | ^^^^^^^^^^
= note: BACKTRACE (of the first span):
- = note: inside `core::slice::<impl [i32]>::get_unchecked::<usize>` at RUSTLIB/core/src/slice/mod.rs:LL:CC
-note: inside `main`
- --> $DIR/zst_slice.rs:LL:CC
- |
-LL | assert_eq!(*s.get_unchecked(1), 2);
- | ^^^^^^^^^^^^^^^^^^
+ = note: inside `main` at RUSTLIB/core/src/macros/mod.rs:LL:CC
+ = note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
diff --git a/src/tools/miri/tests/fail/uninit/uninit_byte_read.rs b/src/tools/miri/tests/fail/uninit/uninit_byte_read.rs
index f1dace0cff9..9bc2b4338b0 100644
--- a/src/tools/miri/tests/fail/uninit/uninit_byte_read.rs
+++ b/src/tools/miri/tests/fail/uninit/uninit_byte_read.rs
@@ -1,7 +1,7 @@
//@compile-flags: -Zmiri-disable-stacked-borrows
fn main() {
let v: Vec<u8> = Vec::with_capacity(10);
- let undef = unsafe { *v.get_unchecked(5) }; //~ ERROR: uninitialized
+ let undef = unsafe { *v.as_ptr().add(5) }; //~ ERROR: uninitialized
let x = undef + 1;
panic!("this should never print: {}", x);
}
diff --git a/src/tools/miri/tests/fail/uninit/uninit_byte_read.stderr b/src/tools/miri/tests/fail/uninit/uninit_byte_read.stderr
index b70f0ad9950..3917d868289 100644
--- a/src/tools/miri/tests/fail/uninit/uninit_byte_read.stderr
+++ b/src/tools/miri/tests/fail/uninit/uninit_byte_read.stderr
@@ -1,8 +1,8 @@
error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
--> $DIR/uninit_byte_read.rs:LL:CC
|
-LL | let undef = unsafe { *v.get_unchecked(5) };
- | ^^^^^^^^^^^^^^^^^^^ using uninitialized data, but this operation requires initialized memory
+LL | let undef = unsafe { *v.as_ptr().add(5) };
+ | ^^^^^^^^^^^^^^^^^^ using uninitialized data, but this operation requires initialized memory
|
= help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
= help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
diff --git a/src/tools/miri/tests/pass/float_nan.rs b/src/tools/miri/tests/pass/float_nan.rs
index 9b0a40c41b9..6ea034e2cda 100644
--- a/src/tools/miri/tests/pass/float_nan.rs
+++ b/src/tools/miri/tests/pass/float_nan.rs
@@ -20,8 +20,8 @@ use NaNKind::*;
#[track_caller]
fn check_all_outcomes<T: Eq + Hash + fmt::Display>(expected: HashSet<T>, generate: impl Fn() -> T) {
let mut seen = HashSet::new();
- // Let's give it 8x as many tries as we are expecting values.
- let tries = expected.len() * 8;
+ // Let's give it sixteen times as many tries as we are expecting values.
+ let tries = expected.len() * 16;
for _ in 0..tries {
let val = generate();
assert!(expected.contains(&val), "got an unexpected value: {val}");
diff --git a/tests/codegen/issues/issue-116878.rs b/tests/codegen/issues/issue-116878.rs
new file mode 100644
index 00000000000..d5f679459f7
--- /dev/null
+++ b/tests/codegen/issues/issue-116878.rs
@@ -0,0 +1,13 @@
+// no-system-llvm
+// compile-flags: -O
+// ignore-debug: the debug assertions get in the way
+#![crate_type = "lib"]
+
+/// Make sure no bounds checks are emitted after a `get_unchecked`.
+// CHECK-LABEL: @unchecked_slice_no_bounds_check
+#[no_mangle]
+pub unsafe fn unchecked_slice_no_bounds_check(s: &[u8]) -> u8 {
+ let a = *s.get_unchecked(1);
+ // CHECK-NOT: panic_bounds_check
+ a + s[0]
+}