Auto merge of rust-lang#53424 - RalfJung:miri-refactor, r=oli-obk

CTFE engine refactor

* Value gets renamed to `Operand`, so that now `interpret::{Place, Operand}` are the "dynamic" versions of `mir::{Place, Operand}`.
* `Operand` and `Place` share the data for their "stuff is in memory"-base in a new type, `MemPlace`. This also makes it possible to give some more precise types in other areas. Both `Operand` and `MemPlace` have methods available to project into fields (and other kinds of projections) without causing further allocations.
* The type for "a `Scalar` or a `ScalarPair`" is called `Value`, and again used to give some more precise types.
* All of these have versions with an attached layout, so that we can more often drag the layout along instead of recomputing it. This lets us get rid of `PlaceExtra::Downcast`. `MPlaceTy` and `PlaceTy` can only be constructed in place.rs, making sure the layout is handled properly. (The same should eventually be done for `ValTy` and `OpTy`.)
 This is used to check, when copying an operand to a place, that the sizes match (which caught a bunch of bugs).
* All the high-level functions to write typed memory take a `Place`, and live in `place.rs`. All the high-level typed functions to read typed memory take an `Operand`, and live in `operands.rs`.
* Remove `cur_frame` and handling of signedess from memory (catching a bug in the float casting code).
* [Only functional change] Enable sanity check to recurse below dyn traits and slices.

r? @oli-obk

Cc @eddyb

Author: bors

src/librustc/dep_graph/dep_node.rs

@@ -632,7 +632,7 @@ define_dep_nodes!( <'tcx>
     // queries). Making them anonymous avoids hashing the result, which
     // may save a bit of time.
     [anon] EraseRegionsTy { ty: Ty<'tcx> },
-    [anon] ConstValueToAllocation { val: &'tcx ty::Const<'tcx> },
+    [anon] ConstToAllocation { val: &'tcx ty::Const<'tcx> },
 
     [input] Freevars(DefId),
     [input] MaybeUnusedTraitImport(DefId),

src/librustc/ich/impls_ty.rs

@@ -397,12 +397,6 @@ impl_stable_hash_for!(enum mir::interpret::ScalarMaybeUndef {
     Undef
 });
 
-impl_stable_hash_for!(enum mir::interpret::Value {
-    Scalar(v),
-    ScalarPair(a, b),
-    ByRef(ptr, align)
-});
-
 impl_stable_hash_for!(struct mir::interpret::Pointer {
     alloc_id,
     offset

src/librustc/mir/interpret/mod.rs

@@ -13,7 +13,7 @@ pub use self::error::{
     FrameInfo, ConstEvalResult,
 };
 
-pub use self::value::{Scalar, Value, ConstValue, ScalarMaybeUndef};
+pub use self::value::{Scalar, ConstValue, ScalarMaybeUndef};
 
 use std::fmt;
 use mir;
@@ -135,7 +135,7 @@ impl<'tcx> Pointer {
         Pointer { alloc_id, offset }
     }
 
-    pub(crate) fn wrapping_signed_offset<C: HasDataLayout>(self, i: i64, cx: C) -> Self {
+    pub fn wrapping_signed_offset<C: HasDataLayout>(self, i: i64, cx: C) -> Self {
         Pointer::new(
             self.alloc_id,
             Size::from_bytes(cx.data_layout().wrapping_signed_offset(self.offset.bytes(), i)),
@@ -147,7 +147,7 @@ impl<'tcx> Pointer {
         (Pointer::new(self.alloc_id, Size::from_bytes(res)), over)
     }
 
-    pub(crate) fn signed_offset<C: HasDataLayout>(self, i: i64, cx: C) -> EvalResult<'tcx, Self> {
+    pub fn signed_offset<C: HasDataLayout>(self, i: i64, cx: C) -> EvalResult<'tcx, Self> {
         Ok(Pointer::new(
             self.alloc_id,
             Size::from_bytes(cx.data_layout().signed_offset(self.offset.bytes(), i)?),
@@ -567,25 +567,33 @@ pub fn write_target_uint(
     }
 }
 
-pub fn write_target_int(
-    endianness: layout::Endian,
-    mut target: &mut [u8],
-    data: i128,
-) -> Result<(), io::Error> {
-    let len = target.len();
-    match endianness {
-        layout::Endian::Little => target.write_int128::<LittleEndian>(data, len),
-        layout::Endian::Big => target.write_int128::<BigEndian>(data, len),
-    }
-}
-
 pub fn read_target_uint(endianness: layout::Endian, mut source: &[u8]) -> Result<u128, io::Error> {
     match endianness {
         layout::Endian::Little => source.read_uint128::<LittleEndian>(source.len()),
         layout::Endian::Big => source.read_uint128::<BigEndian>(source.len()),
     }
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// Methods to faciliate working with signed integers stored in a u128
+////////////////////////////////////////////////////////////////////////////////
+
+pub fn sign_extend(value: u128, size: Size) -> u128 {
+    let size = size.bits();
+    // sign extend
+    let shift = 128 - size;
+    // shift the unsigned value to the left
+    // and back to the right as signed (essentially fills with FF on the left)
+    (((value << shift) as i128) >> shift) as u128
+}
+
+pub fn truncate(value: u128, size: Size) -> u128 {
+    let size = size.bits();
+    let shift = 128 - size;
+    // truncate (shift left to drop out leftover values, shift right to fill with zeroes)
+    (value << shift) >> shift
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Undefined byte tracking
 ////////////////////////////////////////////////////////////////////////////////