Auto merge of #2663 - RalfJung:sync, r=RalfJung

pthread: slight refactoring of how we access the sync object fields

Author: bors

src/concurrency/data_race.rs

@@ -49,7 +49,7 @@ use std::{
 use rustc_ast::Mutability;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_index::vec::{Idx, IndexVec};
-use rustc_middle::{mir, ty::layout::TyAndLayout};
+use rustc_middle::mir;
 use rustc_target::abi::{Align, Size};
 
 use crate::*;
@@ -440,33 +440,6 @@ impl MemoryCellClocks {
 /// Evaluation context extensions.
 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for MiriInterpCx<'mir, 'tcx> {}
 pub trait EvalContextExt<'mir, 'tcx: 'mir>: MiriInterpCxExt<'mir, 'tcx> {
-    /// Atomic variant of read_scalar_at_offset.
-    fn read_scalar_at_offset_atomic(
-        &self,
-        op: &OpTy<'tcx, Provenance>,
-        offset: u64,
-        layout: TyAndLayout<'tcx>,
-        atomic: AtomicReadOrd,
-    ) -> InterpResult<'tcx, Scalar<Provenance>> {
-        let this = self.eval_context_ref();
-        let value_place = this.deref_operand_and_offset(op, offset, layout)?;
-        this.read_scalar_atomic(&value_place, atomic)
-    }
-
-    /// Atomic variant of write_scalar_at_offset.
-    fn write_scalar_at_offset_atomic(
-        &mut self,
-        op: &OpTy<'tcx, Provenance>,
-        offset: u64,
-        value: impl Into<Scalar<Provenance>>,
-        layout: TyAndLayout<'tcx>,
-        atomic: AtomicWriteOrd,
-    ) -> InterpResult<'tcx> {
-        let this = self.eval_context_mut();
-        let value_place = this.deref_operand_and_offset(op, offset, layout)?;
-        this.write_scalar_atomic(value.into(), &value_place, atomic)
-    }
-
     /// Perform an atomic read operation at the memory location.
     fn read_scalar_atomic(
         &self,

src/concurrency/sync.rs

@@ -193,8 +193,9 @@ impl<'mir, 'tcx: 'mir> EvalContextExtPriv<'mir, 'tcx> for crate::MiriInterpCx<'m
 pub(super) trait EvalContextExtPriv<'mir, 'tcx: 'mir>:
     crate::MiriInterpCxExt<'mir, 'tcx>
 {
+    /// Lazily initialize the ID of this Miri sync structure.
+    /// ('0' indicates uninit.)
     #[inline]
-    // Miri sync structures contain zero-initialized ids stored at some offset behind a pointer
     fn get_or_create_id<Id: SyncId>(
         &mut self,
         next_id: Id,
@@ -205,6 +206,7 @@ pub(super) trait EvalContextExtPriv<'mir, 'tcx: 'mir>:
         let value_place =
             this.deref_operand_and_offset(lock_op, offset, this.machine.layouts.u32)?;
 
+        // Since we are lazy, this update has to be atomic.
         let (old, success) = this
             .atomic_compare_exchange_scalar(
                 &value_place,

src/helpers.rs

@@ -667,7 +667,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         layout: TyAndLayout<'tcx>,
     ) -> InterpResult<'tcx, MPlaceTy<'tcx, Provenance>> {
         let this = self.eval_context_ref();
-        let op_place = this.deref_operand(op)?;
+        let op_place = this.deref_operand(op)?; // FIXME: we still deref with the original type!
         let offset = Size::from_bytes(offset);
 
         // Ensure that the access is within bounds.
@@ -687,25 +687,16 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         this.read_scalar(&value_place.into())
     }
 
-    fn write_immediate_at_offset(
-        &mut self,
-        op: &OpTy<'tcx, Provenance>,
-        offset: u64,
-        value: &ImmTy<'tcx, Provenance>,
-    ) -> InterpResult<'tcx, ()> {
-        let this = self.eval_context_mut();
-        let value_place = this.deref_operand_and_offset(op, offset, value.layout)?;
-        this.write_immediate(**value, &value_place.into())
-    }
-
     fn write_scalar_at_offset(
         &mut self,
         op: &OpTy<'tcx, Provenance>,
         offset: u64,
         value: impl Into<Scalar<Provenance>>,
         layout: TyAndLayout<'tcx>,
     ) -> InterpResult<'tcx, ()> {
-        self.write_immediate_at_offset(op, offset, &ImmTy::from_scalar(value.into(), layout))
+        let this = self.eval_context_mut();
+        let value_place = this.deref_operand_and_offset(op, offset, layout)?;
+        this.write_scalar(value, &value_place.into())
     }
 
     /// Parse a `timespec` struct and return it as a `std::time::Duration`. It returns `None`