Auto merge of rust-lang#98674 - RalfJung:miri-stacktrace-pruning, r=M…

…ark-Simulacrum

miri: prune some atomic operation and raw pointer details from stacktrace

Since Miri removes `track_caller` frames from the stacktrace, adding that attribute can help make backtraces more readable (similar to how it makes panic locations better). I made them only show up with `cfg(miri)` to make sure the extra arguments induced by `track_caller` do not cause any runtime performance trouble.

This is also testing the waters for whether the libs team is okay with having these attributes in their code, or whether you'd prefer if we find some other way to do this. If you are fine with this, we will probably want to add it to a lot more functions (all the other atomic operations, to start).

Before:
```
error: Undefined Behavior: Data race detected between Atomic Load on Thread(id = 2) and Write on Thread(id = 1) at alloc1727 (current vector clock = VClock([9, 0, 6]), conflicting timestamp = VClock([0, 6]))
    --> /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/sync/atomic.rs:2594:23
     |
2594 |             SeqCst => intrinsics::atomic_load_seqcst(dst),
     |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Data race detected between Atomic Load on Thread(id = 2) and Write on Thread(id = 1) at alloc1727 (current vector clock = VClock([9, 0, 6]), conflicting timestamp = VClock([0, 6]))
     |
     = 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

     = note: inside `std::sync::atomic::atomic_load::<usize>` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/sync/atomic.rs:2594:23
     = note: inside `std::sync::atomic::AtomicUsize::load` at /home/r/.rustup/toolchains/miri/lib/rustlib/src/rust/library/core/src/sync/atomic.rs:1719:26
note: inside closure at ../miri/tests/fail/data_race/atomic_read_na_write_race1.rs:22:13
    --> ../miri/tests/fail/data_race/atomic_read_na_write_race1.rs:22:13
     |
22   |             (&*c.0).load(Ordering::SeqCst)
     |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```

After:
```
error: Undefined Behavior: Data race detected between Atomic Load on Thread(id = 2) and Write on Thread(id = 1) at alloc1727 (current vector clock = VClock([9, 0, 6]), conflicting timestamp = VClock([0, 6]))
  --> tests/fail/data_race/atomic_read_na_write_race1.rs:22:13
   |
22 |             (&*c.0).load(Ordering::SeqCst)
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Data race detected between Atomic Load on Thread(id = 2) and Write on Thread(id = 1) at alloc1727 (current vector clock = VClock([9, 0, 6]), conflicting timestamp = VClock([0, 6]))
   |
   = 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

   = note: inside closure at tests/fail/data_race/atomic_read_na_write_race1.rs:22:13
```

library/core/src/intrinsics.rs

@@ -2625,6 +2625,7 @@ pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
 #[cfg_attr(not(bootstrap), rustc_allowed_through_unstable_modules)]
 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
     extern "rust-intrinsic" {
         #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]

library/core/src/ptr/const_ptr.rs

@@ -1144,6 +1144,7 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn read(self) -> T
     where
         T: Sized,
@@ -1164,6 +1165,7 @@ impl<T: ?Sized> *const T {
     /// [`ptr::read_volatile`]: crate::ptr::read_volatile()
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub unsafe fn read_volatile(self) -> T
     where
         T: Sized,
@@ -1183,6 +1185,7 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn read_unaligned(self) -> T
     where
         T: Sized,

library/core/src/ptr/mod.rs

@@ -1095,6 +1095,7 @@ pub const unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn read<T>(src: *const T) -> T {
     // We are calling the intrinsics directly to avoid function calls in the generated code
     // as `intrinsics::copy_nonoverlapping` is a wrapper function.
@@ -1194,6 +1195,7 @@ pub const unsafe fn read<T>(src: *const T) -> T {
 #[inline]
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
 #[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn read_unaligned<T>(src: *const T) -> T {
     let mut tmp = MaybeUninit::<T>::uninit();
     // SAFETY: the caller must guarantee that `src` is valid for reads.
@@ -1290,6 +1292,7 @@ pub const unsafe fn read_unaligned<T>(src: *const T) -> T {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn write<T>(dst: *mut T, src: T) {
     // We are calling the intrinsics directly to avoid function calls in the generated code
     // as `intrinsics::copy_nonoverlapping` is a wrapper function.
@@ -1387,6 +1390,7 @@ pub const unsafe fn write<T>(dst: *mut T, src: T) {
 #[inline]
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
     // SAFETY: the caller must guarantee that `dst` is valid for writes.
     // `dst` cannot overlap `src` because the caller has mutable access
@@ -1460,6 +1464,7 @@ pub const unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
 /// ```
 #[inline]
 #[stable(feature = "volatile", since = "1.9.0")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn read_volatile<T>(src: *const T) -> T {
     // SAFETY: the caller must uphold the safety contract for `volatile_load`.
     unsafe {
@@ -1530,6 +1535,7 @@ pub unsafe fn read_volatile<T>(src: *const T) -> T {
 /// ```
 #[inline]
 #[stable(feature = "volatile", since = "1.9.0")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn write_volatile<T>(dst: *mut T, src: T) {
     // SAFETY: the caller must uphold the safety contract for `volatile_store`.
     unsafe {

library/core/src/ptr/mut_ptr.rs

@@ -1258,6 +1258,7 @@ impl<T: ?Sized> *mut T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
     #[inline(always)]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn read(self) -> T
     where
         T: Sized,
@@ -1278,6 +1279,7 @@ impl<T: ?Sized> *mut T {
     /// [`ptr::read_volatile`]: crate::ptr::read_volatile()
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[inline(always)]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub unsafe fn read_volatile(self) -> T
     where
         T: Sized,
@@ -1297,6 +1299,7 @@ impl<T: ?Sized> *mut T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_unstable(feature = "const_ptr_read", issue = "80377")]
     #[inline(always)]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn read_unaligned(self) -> T
     where
         T: Sized,
@@ -1402,6 +1405,7 @@ impl<T: ?Sized> *mut T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
     #[inline(always)]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn write(self, val: T)
     where
         T: Sized,
@@ -1420,6 +1424,7 @@ impl<T: ?Sized> *mut T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
     #[inline(always)]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn write_bytes(self, val: u8, count: usize)
     where
         T: Sized,
@@ -1440,6 +1445,7 @@ impl<T: ?Sized> *mut T {
     /// [`ptr::write_volatile`]: crate::ptr::write_volatile()
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[inline(always)]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub unsafe fn write_volatile(self, val: T)
     where
         T: Sized,
@@ -1459,6 +1465,7 @@ impl<T: ?Sized> *mut T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
     #[inline(always)]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn write_unaligned(self, val: T)
     where
         T: Sized,