Add in atomic_{min,max}_x intrinsics

Co-authored-by: Greg Bowyer <gbowyer@fastmail.co.uk>

Author: henryboisdequin

src/data_race.rs

@@ -74,9 +74,9 @@ use rustc_middle::{mir, ty::layout::TyAndLayout};
 use rustc_target::abi::Size;
 
 use crate::{
-    ImmTy, Immediate, InterpResult, MPlaceTy, MemPlaceMeta, MiriEvalContext, MiriEvalContextExt,
-    OpTy, Pointer, RangeMap, Scalar, ScalarMaybeUninit, Tag, ThreadId, VClock, VTimestamp,
-    VectorIdx, MemoryKind, MiriMemoryKind
+    ImmTy, Immediate, InterpResult, MPlaceTy, MemPlaceMeta, MemoryKind, MiriEvalContext,
+    MiriEvalContextExt, MiriMemoryKind, OpTy, Pointer, RangeMap, Scalar, ScalarMaybeUninit, Tag,
+    ThreadId, VClock, VTimestamp, VectorIdx,
 };
 
 pub type AllocExtra = VClockAlloc;
@@ -542,6 +542,34 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
         Ok(old)
     }
 
+    /// Perform an conditional atomic exchange with a memory place and a new
+    /// scalar value, the old value is returned.
+    fn atomic_min_max_scalar(
+        &mut self,
+        place: &MPlaceTy<'tcx, Tag>,
+        rhs: ImmTy<'tcx, Tag>,
+        min: bool,
+        atomic: AtomicRwOp,
+    ) -> InterpResult<'tcx, ImmTy<'tcx, Tag>> {
+        let this = self.eval_context_mut();
+
+        let old = this.allow_data_races_mut(|this| this.read_immediate(&place.into()))?;
+        let lt = this.overflowing_binary_op(mir::BinOp::Lt, &old, &rhs)?.0.to_bool()?;
+
+        let new_val = if min {
+            if lt { &old } else { &rhs }
+        } else {
+            if lt { &rhs } else { &old }
+        };
+
+        this.allow_data_races_mut(|this| this.write_immediate_to_mplace(**new_val, place))?;
+
+        this.validate_atomic_rmw(&place, atomic)?;
+
+        // Return the old value.
+        Ok(old)
+    }
+
     /// Perform an atomic compare and exchange at a given memory location.
     /// On success an atomic RMW operation is performed and on failure
     /// only an atomic read occurs. If `can_fail_spuriously` is true,
@@ -687,15 +715,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
         }
     }
 
-    fn reset_vector_clocks(
-        &mut self,
-        ptr: Pointer<Tag>,
-        size: Size
-    ) -> InterpResult<'tcx> {
+    fn reset_vector_clocks(&mut self, ptr: Pointer<Tag>, size: Size) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
         if let Some(data_race) = &mut this.memory.extra.data_race {
             if data_race.multi_threaded.get() {
-                let alloc_meta = this.memory.get_raw_mut(ptr.alloc_id)?.extra.data_race.as_mut().unwrap();
+                let alloc_meta =
+                    this.memory.get_raw_mut(ptr.alloc_id)?.extra.data_race.as_mut().unwrap();
                 alloc_meta.reset_clocks(ptr.offset, size);
             }
         }
@@ -715,28 +740,37 @@ pub struct VClockAlloc {
 
 impl VClockAlloc {
     /// Create a new data-race detector for newly allocated memory.
-    pub fn new_allocation(global: &MemoryExtra, len: Size, kind: MemoryKind<MiriMemoryKind>) -> VClockAlloc {
+    pub fn new_allocation(
+        global: &MemoryExtra,
+        len: Size,
+        kind: MemoryKind<MiriMemoryKind>,
+    ) -> VClockAlloc {
         let (alloc_timestamp, alloc_index) = match kind {
             // User allocated and stack memory should track allocation.
             MemoryKind::Machine(
-                MiriMemoryKind::Rust | MiriMemoryKind::C | MiriMemoryKind::WinHeap
-            ) | MemoryKind::Stack => {
+                MiriMemoryKind::Rust | MiriMemoryKind::C | MiriMemoryKind::WinHeap,
+            )
+            | MemoryKind::Stack => {
                 let (alloc_index, clocks) = global.current_thread_state();
                 let alloc_timestamp = clocks.clock[alloc_index];
                 (alloc_timestamp, alloc_index)
             }
             // Other global memory should trace races but be allocated at the 0 timestamp.
             MemoryKind::Machine(
-                MiriMemoryKind::Global | MiriMemoryKind::Machine | MiriMemoryKind::Env |
-                MiriMemoryKind::ExternStatic | MiriMemoryKind::Tls
-            ) | MemoryKind::CallerLocation | MemoryKind::Vtable => {
-                (0, VectorIdx::MAX_INDEX)
-            }
+                MiriMemoryKind::Global
+                | MiriMemoryKind::Machine
+                | MiriMemoryKind::Env
+                | MiriMemoryKind::ExternStatic
+                | MiriMemoryKind::Tls,
+            )
+            | MemoryKind::CallerLocation
+            | MemoryKind::Vtable => (0, VectorIdx::MAX_INDEX),
         };
         VClockAlloc {
             global: Rc::clone(global),
             alloc_ranges: RefCell::new(RangeMap::new(
-                len, MemoryCellClocks::new(alloc_timestamp, alloc_index)
+                len,
+                MemoryCellClocks::new(alloc_timestamp, alloc_index),
             )),
         }
     }
@@ -1015,7 +1049,8 @@ trait EvalContextPrivExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
                                 true,
                                 place_ptr,
                                 size,
-                            ).map(|_| true);
+                            )
+                            .map(|_| true);
                         }
                     }
 
@@ -1267,7 +1302,6 @@ impl GlobalState {
             .as_ref()
             .expect("Joined with thread but thread has not terminated");
 
-
         // The join thread happens-before the current thread
         // so update the current vector clock.
         // Is not a release operation so the clock is not incremented.