Fix span management

Author: saethlin

src/tools/miri/src/concurrency/data_race.rs

@@ -51,7 +51,6 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_middle::mir;
 use rustc_span::Span;
-use rustc_span::DUMMY_SP;
 use rustc_target::abi::{Align, Size};
 
 use crate::diagnostics::RacingOp;
@@ -398,7 +397,10 @@ impl MemoryCellClocks {
         current_span: Span,
     ) -> Result<(), DataRace> {
         log::trace!("Unsynchronized read with vectors: {:#?} :: {:#?}", self, clocks);
-        let res = if self.write <= clocks.clock[self.write_index] {
+        if !current_span.is_dummy() {
+            clocks.clock[index].span = current_span;
+        }
+        if self.write <= clocks.clock[self.write_index] {
             let race_free = if let Some(atomic) = self.atomic() {
                 atomic.write_vector <= clocks.clock
             } else {
@@ -408,11 +410,7 @@ impl MemoryCellClocks {
             if race_free { Ok(()) } else { Err(DataRace) }
         } else {
             Err(DataRace)
-        };
-        if res.is_ok() && current_span != DUMMY_SP {
-            clocks.clock[index].span = current_span;
         }
-        res
     }
 
     /// Detect races for non-atomic write operations at the current memory cell
@@ -425,7 +423,7 @@ impl MemoryCellClocks {
         current_span: Span,
     ) -> Result<(), DataRace> {
         log::trace!("Unsynchronized write with vectors: {:#?} :: {:#?}", self, clocks);
-        if current_span != DUMMY_SP {
+        if !current_span.is_dummy() {
             clocks.clock[index].span = current_span;
         }
         if self.write <= clocks.clock[self.write_index] && self.read <= clocks.clock {
@@ -712,9 +710,7 @@ impl VClockAlloc {
             | MemoryKind::Stack => {
                 let (alloc_index, clocks) = global.current_thread_state(thread_mgr);
                 let mut alloc_timestamp = clocks.clock[alloc_index];
-                if current_span != DUMMY_SP {
-                    alloc_timestamp.span = current_span;
-                }
+                alloc_timestamp.span = current_span;
                 (alloc_timestamp, alloc_index)
             }
             // Other global memory should trace races but be allocated at the 0 timestamp.

src/tools/miri/src/concurrency/vector_clock.rs

@@ -45,8 +45,9 @@ impl From<u32> for VectorIdx {
 /// clock vectors larger than this will be stored on the heap
 const SMALL_VECTOR: usize = 4;
 
-/// The type of the time-stamps recorded in the data-race detector
-/// set to a type of unsigned integer
+/// The time-stamps recorded in the data-race detector consist of both
+/// a 32-bit unsigned integer which is the actual timestamp, and a `Span`
+/// so that diagnostics can report what code was responsible for an operation.
 #[derive(Clone, Copy, Debug, Eq)]
 pub struct VTimestamp {
     time: u32,
@@ -128,7 +129,7 @@ impl VClock {
         let mut_slice = self.get_mut_with_min_len(idx + 1);
         let idx_ref = &mut mut_slice[idx];
         idx_ref.time = idx_ref.time.checked_add(1).expect("Vector clock overflow");
-        if current_span != DUMMY_SP {
+        if !current_span.is_dummy() {
             idx_ref.span = current_span;
         }
     }
@@ -143,14 +144,7 @@ impl VClock {
             let l_span = l.span;
             let r_span = r.span;
             *l = r.max(*l);
-            if l.span == DUMMY_SP {
-                if r_span != DUMMY_SP {
-                    l.span = r_span;
-                }
-                if l_span != DUMMY_SP {
-                    l.span = l_span;
-                }
-            }
+            l.span = l.span.substitute_dummy(r_span).substitute_dummy(l_span);
         }
     }
 
@@ -162,9 +156,8 @@ impl VClock {
 
         mut_slice[idx.index()] = other[idx];
 
-        if other[idx].span == DUMMY_SP {
-            mut_slice[idx.index()].span = prev_span;
-        }
+        let span = &mut mut_slice[idx.index()].span;
+        *span = span.substitute_dummy(prev_span);
     }
 
     /// Set the vector to the all-zero vector

src/tools/miri/tests/fail/data_race/alloc_read_race.stderr

@@ -8,7 +8,7 @@ help: The Read on thread `<unnamed>` is here
   --> $DIR/alloc_read_race.rs:LL:CC
    |
 LL | ...   *pointer.load(Ordering::Relaxed)
-   |                                      ^
+   |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 help: The Allocate on thread `<unnamed>` is here
   --> $DIR/alloc_read_race.rs:LL:CC
    |

src/tools/miri/tests/fail/data_race/atomic_write_na_read_race1.stderr

@@ -5,10 +5,10 @@ LL |             *atomic_ref.get_mut()
    |             ^^^^^^^^^^^^^^^^^^^^^ Data race detected between Read on thread `<unnamed>` and Atomic Store on thread `<unnamed>` at ALLOC
    |
 help: The Read on thread `<unnamed>` is here
-  --> RUSTLIB/core/src/ptr/mod.rs:LL:CC
+  --> $DIR/atomic_write_na_read_race1.rs:LL:CC
    |
-LL | }
-   | ^
+LL |             *atomic_ref.get_mut()
+   |             ^^^^^^^^^^^^^^^^^^^^^
 help: The Atomic Store on thread `<unnamed>` is here
   --> $DIR/atomic_write_na_read_race1.rs:LL:CC
    |

src/tools/miri/tests/fail/data_race/atomic_write_na_read_race2.stderr

@@ -10,10 +10,10 @@ help: The Atomic Store on thread `<unnamed>` is here
 LL | ...   (&*c.0).store(32, Ordering::SeqCst);
    |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 help: The Read on thread `<unnamed>` is here
-  --> RUSTLIB/core/src/ptr/mod.rs:LL:CC
+  --> $DIR/atomic_write_na_read_race2.rs:LL:CC
    |
-LL | }
-   | ^
+LL |             let _val = *(c.0 as *mut usize);
+   |                        ^^^^^^^^^^^^^^^^^^^^
    = 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: BACKTRACE:

src/tools/miri/tests/fail/data_race/dealloc_read_race1.stderr

@@ -20,10 +20,10 @@ LL | |                 std::mem::align_of::<usize>(),
 LL | |             );
    | |_____________^
 help: The Read on thread `<unnamed>` is here
-  --> RUSTLIB/core/src/ptr/mod.rs:LL:CC
+  --> $DIR/dealloc_read_race1.rs:LL:CC
    |
-LL | }
-   | ^
+LL |             let _val = *ptr.0;
+   |                        ^^^^^^
    = 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: BACKTRACE:

src/tools/miri/tests/fail/data_race/dealloc_read_race_stack.stderr

@@ -13,7 +13,7 @@ help: The Read on thread `<unnamed>` is here
   --> $DIR/dealloc_read_race_stack.rs:LL:CC
    |
 LL |             *pointer.load(Ordering::Acquire)
-   |                                            ^
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = 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: BACKTRACE:

src/tools/miri/tests/fail/data_race/read_write_race.stderr

@@ -10,10 +10,10 @@ help: The Write on thread `<unnamed>` is here
 LL |             *c.0 = 64;
    |             ^^^^^^^^^
 help: The Read on thread `<unnamed>` is here
-  --> RUSTLIB/core/src/ptr/mod.rs:LL:CC
+  --> $DIR/read_write_race.rs:LL:CC
    |
-LL | }
-   | ^
+LL |             let _val = *c.0;
+   |                        ^^^^
    = 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: BACKTRACE:

src/tools/miri/tests/fail/data_race/read_write_race_stack.stderr

@@ -7,8 +7,8 @@ LL |             stack_var
 help: The Read on thread `<unnamed>` is here
   --> $DIR/read_write_race_stack.rs:LL:CC
    |
-LL |             sleep(Duration::from_millis(200));
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |             stack_var
+   |             ^^^^^^^^^
 help: The Write on thread `<unnamed>` is here
   --> $DIR/read_write_race_stack.rs:LL:CC
    |

src/tools/miri/tests/fail/data_race/relax_acquire_race.stderr

@@ -7,8 +7,8 @@ LL |                 *c.0
 help: The Read on thread `<unnamed>` is here
   --> $DIR/relax_acquire_race.rs:LL:CC
    |
-LL |             if SYNC.load(Ordering::Acquire) == 2 {
-   |                                           ^
+LL |                 *c.0
+   |                 ^^^^
 help: The Write on thread `<unnamed>` is here
   --> $DIR/relax_acquire_race.rs:LL:CC
    |