Merge branch 'gvn-borrowed'

Author: cjgillot

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -416,7 +416,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         }
     }
 
-    fn unsize_into(
+    pub fn unsize_into(
         &mut self,
         src: &OpTy<'tcx, M::Provenance>,
         cast_ty: TyAndLayout<'tcx>,

compiler/rustc_mir_transform/src/copy_prop.rs

@@ -112,6 +112,9 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
 
     fn visit_local(&mut self, local: &mut Local, ctxt: PlaceContext, _: Location) {
         let new_local = self.copy_classes[*local];
+        if self.borrowed_locals.contains(*local) {
+            return;
+        }
         match ctxt {
             // Do not modify the local in storage statements.
             PlaceContext::NonUse(NonUseContext::StorageLive | NonUseContext::StorageDead) => {}
@@ -122,32 +125,16 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
         }
     }
 
-    fn visit_place(&mut self, place: &mut Place<'tcx>, ctxt: PlaceContext, loc: Location) {
+    fn visit_place(&mut self, place: &mut Place<'tcx>, _: PlaceContext, loc: Location) {
         if let Some(new_projection) = self.process_projection(place.projection, loc) {
             place.projection = self.tcx().mk_place_elems(&new_projection);
         }
 
-        let observes_address = match ctxt {
-            PlaceContext::NonMutatingUse(
-                NonMutatingUseContext::SharedBorrow
-                | NonMutatingUseContext::FakeBorrow
-                | NonMutatingUseContext::AddressOf,
-            ) => true,
-            // For debuginfo, merging locals is ok.
-            PlaceContext::NonUse(NonUseContext::VarDebugInfo) => {
-                self.borrowed_locals.contains(place.local)
-            }
-            _ => false,
-        };
-        if observes_address && !place.is_indirect() {
-            // We observe the address of `place.local`. Do not replace it.
-        } else {
-            self.visit_local(
-                &mut place.local,
-                PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
-                loc,
-            )
-        }
+        self.visit_local(
+            &mut place.local,
+            PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
+            loc,
+        )
     }
 
     fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) {

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -2,7 +2,9 @@
 //!
 //! Currently, this pass only propagates scalar values.
 
-use rustc_const_eval::interpret::{ImmTy, Immediate, InterpCx, OpTy, PlaceTy, Projectable};
+use rustc_const_eval::interpret::{
+    ImmTy, Immediate, InterpCx, OpTy, PlaceTy, Pointer, PointerArithmetic, Projectable,
+};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::DefKind;
 use rustc_middle::mir::interpret::{AllocId, ConstAllocation, InterpResult, Scalar};
@@ -935,12 +937,64 @@ impl<'mir, 'tcx: 'mir> rustc_const_eval::interpret::Machine<'mir, 'tcx> for Dumm
     }
 
     fn binary_ptr_op(
-        _ecx: &InterpCx<'mir, 'tcx, Self>,
-        _bin_op: BinOp,
-        _left: &rustc_const_eval::interpret::ImmTy<'tcx, Self::Provenance>,
-        _right: &rustc_const_eval::interpret::ImmTy<'tcx, Self::Provenance>,
+        ecx: &InterpCx<'mir, 'tcx, Self>,
+        bin_op: BinOp,
+        left: &rustc_const_eval::interpret::ImmTy<'tcx, Self::Provenance>,
+        right: &rustc_const_eval::interpret::ImmTy<'tcx, Self::Provenance>,
     ) -> interpret::InterpResult<'tcx, (ImmTy<'tcx, Self::Provenance>, bool)> {
-        throw_machine_stop_str!("can't do pointer arithmetic");
+        use rustc_middle::mir::BinOp::*;
+        Ok(match bin_op {
+            Eq | Ne | Lt | Le | Gt | Ge => {
+                assert_eq!(left.layout.abi, right.layout.abi); // types an differ, e.g. fn ptrs with different `for`
+                let size = ecx.pointer_size();
+                // Just compare the bits. ScalarPairs are compared lexicographically.
+                // We thus always compare pairs and simply fill scalars up with 0.
+                let left = match **left {
+                    Immediate::Scalar(l) => (l.to_bits(size)?, 0),
+                    Immediate::ScalarPair(l1, l2) => (l1.to_bits(size)?, l2.to_bits(size)?),
+                    Immediate::Uninit => panic!("we should never see uninit data here"),
+                };
+                let right = match **right {
+                    Immediate::Scalar(r) => (r.to_bits(size)?, 0),
+                    Immediate::ScalarPair(r1, r2) => (r1.to_bits(size)?, r2.to_bits(size)?),
+                    Immediate::Uninit => panic!("we should never see uninit data here"),
+                };
+                let res = match bin_op {
+                    Eq => left == right,
+                    Ne => left != right,
+                    Lt => left < right,
+                    Le => left <= right,
+                    Gt => left > right,
+                    Ge => left >= right,
+                    _ => bug!(),
+                };
+                (ImmTy::from_bool(res, *ecx.tcx), false)
+            }
+
+            // Some more operations are possible with atomics.
+            // The return value always has the provenance of the *left* operand.
+            Add | Sub | BitOr | BitAnd | BitXor => {
+                assert!(left.layout.ty.is_unsafe_ptr());
+                assert!(right.layout.ty.is_unsafe_ptr());
+                let ptr = left.to_scalar().to_pointer(ecx)?;
+                // We do the actual operation with usize-typed scalars.
+                let usize_layout = ecx.layout_of(ecx.tcx.types.usize).unwrap();
+                let left = ImmTy::from_uint(ptr.addr().bytes(), usize_layout);
+                let right = ImmTy::from_uint(right.to_scalar().to_target_usize(ecx)?, usize_layout);
+                let (result, overflowing) = ecx.overflowing_binary_op(bin_op, &left, &right)?;
+                // Construct a new pointer with the provenance of `ptr` (the LHS).
+                let result_ptr = Pointer::new(
+                    ptr.provenance,
+                    Size::from_bytes(result.to_scalar().to_target_usize(ecx)?),
+                );
+                (
+                    ImmTy::from_scalar(Scalar::from_maybe_pointer(result_ptr, ecx), left.layout),
+                    overflowing,
+                )
+            }
+
+            _ => span_bug!(ecx.cur_span(), "Invalid operator on pointers: {:?}", bin_op),
+        })
     }
 
     fn expose_ptr(