Auto merge of #856 - RalfJung:type_dispatch_first, r=RalfJung

Adjust for ptr_op changes

This is the Miri side of rust-lang/rust#62946.

Author: bors

src/machine.rs

@@ -179,13 +179,13 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'tcx> {
     }
 
     #[inline(always)]
-    fn ptr_op(
+    fn binary_ptr_op(
         ecx: &rustc_mir::interpret::InterpCx<'mir, 'tcx, Self>,
         bin_op: mir::BinOp,
         left: ImmTy<'tcx, Tag>,
         right: ImmTy<'tcx, Tag>,
     ) -> InterpResult<'tcx, (Scalar<Tag>, bool)> {
-        ecx.ptr_op(bin_op, left, right)
+        ecx.binary_ptr_op(bin_op, left, right)
     }
 
     fn box_alloc(

src/operator.rs

@@ -1,4 +1,4 @@
-use rustc::ty::{Ty, layout::{Size, LayoutOf}};
+use rustc::ty::{Ty, layout::LayoutOf};
 use rustc::mir;
 
 use crate::*;
@@ -9,21 +9,13 @@ pub trait EvalContextExt<'tcx> {
         ptr: Pointer<Tag>
     ) -> InterpResult<'tcx>;
 
-    fn ptr_op(
+    fn binary_ptr_op(
         &self,
         bin_op: mir::BinOp,
         left: ImmTy<'tcx, Tag>,
         right: ImmTy<'tcx, Tag>,
     ) -> InterpResult<'tcx, (Scalar<Tag>, bool)>;
 
-    fn ptr_int_arithmetic(
-        &self,
-        bin_op: mir::BinOp,
-        left: Pointer<Tag>,
-        right: u128,
-        signed: bool,
-    ) -> InterpResult<'tcx, (Scalar<Tag>, bool)>;
-
     fn ptr_eq(
         &self,
         left: Scalar<Tag>,
@@ -46,7 +38,7 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
         ptr.check_in_alloc(size, CheckInAllocMsg::InboundsTest)
     }
 
-    fn ptr_op(
+    fn binary_ptr_op(
         &self,
         bin_op: mir::BinOp,
         left: ImmTy<'tcx, Tag>,
@@ -56,24 +48,9 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
 
         trace!("ptr_op: {:?} {:?} {:?}", *left, bin_op, *right);
 
-        // Treat everything of integer *type* at integer *value*.
-        if left.layout.ty.is_integral() {
-            // This is actually an integer operation, so dispatch back to the core engine.
-            // TODO: Once intptrcast is the default, librustc_mir should never even call us
-            // for integer types.
-            assert!(right.layout.ty.is_integral());
-            let l_bits = self.force_bits(left.imm.to_scalar()?, left.layout.size)?;
-            let r_bits = self.force_bits(right.imm.to_scalar()?, right.layout.size)?;
-
-            let left = ImmTy::from_scalar(Scalar::from_uint(l_bits, left.layout.size), left.layout);
-            let right = ImmTy::from_scalar(Scalar::from_uint(r_bits, left.layout.size), right.layout);
-
-            return self.binary_op(bin_op, left, right);
-        }
-
-        // Operations that support fat pointers
-        match bin_op {
+        Ok(match bin_op {
             Eq | Ne => {
+                // This supports fat pointers.
                 let eq = match (*left, *right) {
                     (Immediate::Scalar(left), Immediate::Scalar(right)) =>
                         self.ptr_eq(left.not_undef()?, right.not_undef()?)?,
@@ -82,103 +59,38 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
                         self.ptr_eq(left2.not_undef()?, right2.not_undef()?)?,
                     _ => bug!("Type system should not allow comparing Scalar with ScalarPair"),
                 };
-                return Ok((Scalar::from_bool(if bin_op == Eq { eq } else { !eq }), false));
+                (Scalar::from_bool(if bin_op == Eq { eq } else { !eq }), false)
             }
-            _ => {},
-        }
 
-        // Now we expect no more fat pointers.
-        let left_layout = left.layout;
-        let left = left.to_scalar()?;
-        let right_layout = right.layout;
-        let right = right.to_scalar()?;
-        debug_assert!(left.is_ptr() || right.is_ptr() || bin_op == Offset);
+            Lt | Le | Gt | Ge => {
+                // Just compare the integers.
+                // TODO: Do we really want to *always* do that, even when comparing two live in-bounds pointers?
+                let left = self.force_bits(left.to_scalar()?, left.layout.size)?;
+                let right = self.force_bits(right.to_scalar()?, right.layout.size)?;
+                let res = match bin_op {
+                    Lt => left < right,
+                    Le => left <= right,
+                    Gt => left > right,
+                    Ge => left >= right,
+                    _ => bug!("We already established it has to be one of these operators."),
+                };
+                (Scalar::from_bool(res), false)
+            }
 
-        Ok(match bin_op {
             Offset => {
-                let pointee_ty = left_layout.ty
+                let pointee_ty = left.layout.ty
                     .builtin_deref(true)
                     .expect("Offset called on non-ptr type")
                     .ty;
                 let ptr = self.pointer_offset_inbounds(
-                    left,
+                    left.to_scalar()?,
                     pointee_ty,
-                    right.to_isize(self)?,
+                    right.to_scalar()?.to_isize(self)?,
                 )?;
                 (ptr, false)
             }
-            // These need both to be pointer, and fail if they are not in the same location
-            Lt | Le | Gt | Ge | Sub if left.is_ptr() && right.is_ptr() => {
-                let left = left.to_ptr().expect("we checked is_ptr");
-                let right = right.to_ptr().expect("we checked is_ptr");
-                if left.alloc_id == right.alloc_id {
-                    let res = match bin_op {
-                        Lt => left.offset < right.offset,
-                        Le => left.offset <= right.offset,
-                        Gt => left.offset > right.offset,
-                        Ge => left.offset >= right.offset,
-                        Sub => {
-                            // subtract the offsets
-                            let left_offset = Scalar::from_uint(left.offset.bytes(), self.memory().pointer_size());
-                            let right_offset = Scalar::from_uint(right.offset.bytes(), self.memory().pointer_size());
-                            let layout = self.layout_of(self.tcx.types.usize)?;
-                            return self.binary_op(
-                                Sub,
-                                ImmTy::from_scalar(left_offset, layout),
-                                ImmTy::from_scalar(right_offset, layout),
-                            )
-                        }
-                        _ => bug!("We already established it has to be one of these operators."),
-                    };
-                    (Scalar::from_bool(res), false)
-                } else {
-                    // Both are pointers, but from different allocations.
-                    throw_unsup!(InvalidPointerMath)
-                }
-            }
-            Gt | Ge if left.is_ptr() && right.is_bits() => {
-                // "ptr >[=] integer" can be tested if the integer is small enough.
-                let left = left.to_ptr().expect("we checked is_ptr");
-                let right = right.to_bits(self.memory().pointer_size()).expect("we checked is_bits");
-                let (_alloc_size, alloc_align) = self.memory()
-                    .get_size_and_align(left.alloc_id, AllocCheck::MaybeDead)
-                    .expect("alloc info with MaybeDead cannot fail");
-                let min_ptr_val = u128::from(alloc_align.bytes()) + u128::from(left.offset.bytes());
-                let result = match bin_op {
-                    Gt => min_ptr_val > right,
-                    Ge => min_ptr_val >= right,
-                    _ => bug!(),
-                };
-                if result {
-                    // Definitely true!
-                    (Scalar::from_bool(true), false)
-                } else {
-                    // Sorry, can't tell.
-                    throw_unsup!(InvalidPointerMath)
-                }
-            }
-            // These work if the left operand is a pointer, and the right an integer
-            Add | BitAnd | Sub | Rem if left.is_ptr() && right.is_bits() => {
-                // Cast to i128 is fine as we checked the kind to be ptr-sized
-                self.ptr_int_arithmetic(
-                    bin_op,
-                    left.to_ptr().expect("we checked is_ptr"),
-                    right.to_bits(self.memory().pointer_size()).expect("we checked is_bits"),
-                    right_layout.abi.is_signed(),
-                )?
-            }
-            // Commutative operators also work if the integer is on the left
-            Add | BitAnd if left.is_bits() && right.is_ptr() => {
-                // This is a commutative operation, just swap the operands
-                self.ptr_int_arithmetic(
-                    bin_op,
-                    right.to_ptr().expect("we checked is_ptr"),
-                    left.to_bits(self.memory().pointer_size()).expect("we checked is_bits"),
-                    left_layout.abi.is_signed(),
-                )?
-            }
-            // Nothing else works
-            _ => throw_unsup!(InvalidPointerMath),
+
+            _ => bug!("Invalid operator on pointers: {:?}", bin_op)
         })
     }
 
@@ -195,99 +107,6 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
         Ok(left == right)
     }
 
-    fn ptr_int_arithmetic(
-        &self,
-        bin_op: mir::BinOp,
-        left: Pointer<Tag>,
-        right: u128,
-        signed: bool,
-    ) -> InterpResult<'tcx, (Scalar<Tag>, bool)> {
-        use rustc::mir::BinOp::*;
-
-        fn map_to_primval((res, over): (Pointer<Tag>, bool)) -> (Scalar<Tag>, bool) {
-            (Scalar::Ptr(res), over)
-        }
-
-        Ok(match bin_op {
-            Sub =>
-                // The only way this can overflow is by underflowing, so signdeness of the right
-                // operands does not matter.
-                map_to_primval(left.overflowing_signed_offset(-(right as i128), self)),
-            Add if signed =>
-                map_to_primval(left.overflowing_signed_offset(right as i128, self)),
-            Add if !signed =>
-                map_to_primval(left.overflowing_offset(Size::from_bytes(right as u64), self)),
-
-            BitAnd if !signed => {
-                let ptr_base_align = self.memory().get_size_and_align(left.alloc_id, AllocCheck::MaybeDead)
-                    .expect("alloc info with MaybeDead cannot fail")
-                    .1.bytes();
-                let base_mask = {
-                    // FIXME: use `interpret::truncate`, once that takes a `Size` instead of a `Layout`.
-                    let shift = 128 - self.memory().pointer_size().bits();
-                    let value = !(ptr_base_align as u128 - 1);
-                    // Truncate (shift left to drop out leftover values, shift right to fill with zeroes).
-                    (value << shift) >> shift
-                };
-                let ptr_size = self.memory().pointer_size();
-                trace!("ptr BitAnd, align {}, operand {:#010x}, base_mask {:#010x}",
-                    ptr_base_align, right, base_mask);
-                if right & base_mask == base_mask {
-                    // Case 1: the base address bits are all preserved, i.e., right is all-1 there.
-                    let offset = (left.offset.bytes() as u128 & right) as u64;
-                    (
-                        Scalar::Ptr(Pointer::new_with_tag(
-                            left.alloc_id,
-                            Size::from_bytes(offset),
-                            left.tag,
-                        )),
-                        false,
-                    )
-                } else if right & base_mask == 0 {
-                    // Case 2: the base address bits are all taken away, i.e., right is all-0 there.
-                    let v = Scalar::from_uint((left.offset.bytes() as u128) & right, ptr_size);
-                    (v, false)
-                } else {
-                    throw_unsup!(ReadPointerAsBytes);
-                }
-            }
-
-            Rem if !signed => {
-                // Doing modulo a divisor of the alignment is allowed.
-                // (Intuition: modulo a divisor leaks less information.)
-                let ptr_base_align = self.memory().get_size_and_align(left.alloc_id, AllocCheck::MaybeDead)
-                    .expect("alloc info with MaybeDead cannot fail")
-                    .1.bytes();
-                let right = right as u64;
-                let ptr_size = self.memory().pointer_size();
-                if right == 1 {
-                    // Modulo 1 is always 0.
-                    (Scalar::from_uint(0u32, ptr_size), false)
-                } else if ptr_base_align % right == 0 {
-                    // The base address would be cancelled out by the modulo operation, so we can
-                    // just take the modulo of the offset.
-                    (
-                        Scalar::from_uint((left.offset.bytes() % right) as u128, ptr_size),
-                        false,
-                    )
-                } else {
-                    throw_unsup!(ReadPointerAsBytes);
-                }
-            }
-
-            _ => {
-                let msg = format!(
-                    "unimplemented binary op on pointer {:?}: {:?}, {:?} ({})",
-                    bin_op,
-                    left,
-                    right,
-                    if signed { "signed" } else { "unsigned" }
-                );
-                throw_unsup!(Unimplemented(msg));
-            }
-        })
-    }
-
     /// Raises an error if the offset moves the pointer outside of its allocation.
     /// We consider ZSTs their own huge allocation that doesn't overlap with anything (and nothing
     /// moves in there because the size is 0). We also consider the NULL pointer its own separate

src/shims/intrinsics.rs

@@ -306,7 +306,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                     match dest.layout.abi {
                         layout::Abi::Scalar(ref s) => {
                             let x = Scalar::from_int(0, s.value.size(this));
-                            this.write_immediate(Immediate::Scalar(x.into()), dest)?;
+                            this.write_scalar(x, dest)?;
                         }
                         layout::Abi::ScalarPair(ref s1, ref s2) => {
                             let x = Scalar::from_int(0, s1.value.size(this));