Const to op simplification

src/librustc/ich/impls_ty.rs

@@ -307,7 +307,7 @@ impl_stable_hash_for!(
     impl<'tcx> for enum mir::interpret::ConstValue<'tcx> [ mir::interpret::ConstValue ] {
         Scalar(val),
         Slice(a, b),
-        ByRef(id, alloc, offset),
+        ByRef(ptr, alloc),
     }
 );
 impl_stable_hash_for!(struct crate::mir::interpret::RawConst<'tcx> {

src/librustc/mir/interpret/value.rs

@@ -31,9 +31,9 @@ pub enum ConstValue<'tcx> {
     /// it.
     Slice(Scalar, u64),
 
-    /// An allocation together with an offset into the allocation.
-    /// Invariant: the `AllocId` matches the allocation.
-    ByRef(AllocId, &'tcx Allocation, Size),
+    /// An allocation together with a pointer into the allocation.
+    /// Invariant: the pointer's `AllocId` resolves to the allocation.
+    ByRef(Pointer, &'tcx Allocation),
 }
 
 #[cfg(target_arch = "x86_64")]

src/librustc/ty/structural_impls.rs

@@ -499,8 +499,8 @@ impl<'a, 'tcx> Lift<'tcx> for ConstValue<'a> {
         match *self {
             ConstValue::Scalar(x) => Some(ConstValue::Scalar(x)),
             ConstValue::Slice(x, y) => Some(ConstValue::Slice(x, y)),
-            ConstValue::ByRef(x, alloc, z) => Some(ConstValue::ByRef(
-                x, alloc.lift_to_tcx(tcx)?, z,
+            ConstValue::ByRef(ptr, alloc) => Some(ConstValue::ByRef(
+                ptr, alloc.lift_to_tcx(tcx)?,
             )),
         }
     }

src/librustc_codegen_llvm/consts.rs

@@ -71,7 +71,7 @@ pub fn codegen_static_initializer(
     let static_ = cx.tcx.const_eval(param_env.and(cid))?;
 
     let alloc = match static_.val {
-        ConstValue::ByRef(_, alloc, n) if n.bytes() == 0 => alloc,
+        ConstValue::ByRef(ptr, alloc) if ptr.offset.bytes() == 0 => alloc,
         _ => bug!("static const eval returned {:#?}", static_),
     };
     Ok((const_alloc_to_llvm(cx, alloc), alloc))

src/librustc_codegen_ssa/mir/operand.rs

@@ -101,8 +101,8 @@ impl<'a, 'tcx: 'a, V: CodegenObject> OperandRef<'tcx, V> {
                 let b_llval = bx.cx().const_usize(b);
                 OperandValue::Pair(a_llval, b_llval)
             },
-            ConstValue::ByRef(_, alloc, offset) => {
-                return Ok(bx.load_operand(bx.cx().from_const_alloc(layout, alloc, offset)));
+            ConstValue::ByRef(ptr, alloc) => {
+                return Ok(bx.load_operand(bx.cx().from_const_alloc(layout, alloc, ptr.offset)));
             },
         };
 

src/librustc_codegen_ssa/mir/place.rs

@@ -417,8 +417,8 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let layout = cx.layout_of(self.monomorphize(&ty));
                 match bx.tcx().const_eval(param_env.and(cid)) {
                     Ok(val) => match val.val {
-                        mir::interpret::ConstValue::ByRef(_, alloc, offset) => {
-                            bx.cx().from_const_alloc(layout, alloc, offset)
+                        mir::interpret::ConstValue::ByRef(ptr, alloc) => {
+                            bx.cx().from_const_alloc(layout, alloc, ptr.offset)
                         }
                         _ => bug!("promoteds should have an allocation: {:?}", val),
                     },

src/librustc_mir/const_eval.rs

@@ -76,7 +76,7 @@ pub fn op_to_const<'tcx>(
             _ => false,
         };
     let normalized_op = if normalize {
-        ecx.try_read_immediate(op)?
+        Ok(*ecx.read_immediate(op).expect("normalization works on validated constants"))
     } else {
         match *op {
             Operand::Indirect(mplace) => Err(mplace),
@@ -96,7 +96,7 @@ pub fn op_to_const<'tcx>(
             // FIXME shouldn't it be the case that `mark_static_initialized` has already
             // interned this?  I thought that is the entire point of that `FinishStatic` stuff?
             let alloc = ecx.tcx.intern_const_alloc(alloc);
-            ConstValue::ByRef(ptr.alloc_id, alloc, ptr.offset)
+            ConstValue::ByRef(ptr, alloc)
         },
         Ok(Immediate::Scalar(x)) =>
             ConstValue::Scalar(x.not_undef()?),
@@ -476,7 +476,7 @@ pub fn const_field<'a, 'tcx>(
     let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env);
     let result = (|| {
         // get the operand again
-        let op = ecx.lazy_const_to_op(ty::LazyConst::Evaluated(value), value.ty)?;
+        let op = ecx.const_to_op(value, None)?;
         // downcast
         let down = match variant {
             None => op,
@@ -502,7 +502,7 @@ pub fn const_variant_index<'a, 'tcx>(
 ) -> EvalResult<'tcx, VariantIdx> {
     trace!("const_variant_index: {:?}", val);
     let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env);
-    let op = ecx.lazy_const_to_op(ty::LazyConst::Evaluated(val), val.ty)?;
+    let op = ecx.const_to_op(val, None)?;
     Ok(ecx.read_discriminant(op)?.1)
 }
 

src/librustc_mir/hair/pattern/_match.rs

@@ -172,7 +172,7 @@ use rustc::ty::{self, Ty, TyCtxt, TypeFoldable, Const};
 use rustc::ty::layout::{Integer, IntegerExt, VariantIdx, Size};
 
 use rustc::mir::Field;
-use rustc::mir::interpret::{ConstValue, Pointer, Scalar};
+use rustc::mir::interpret::{ConstValue, Scalar};
 use rustc::util::common::ErrorReported;
 
 use syntax::attr::{SignedInt, UnsignedInt};
@@ -214,9 +214,8 @@ impl<'a, 'tcx> LiteralExpander<'a, 'tcx> {
         match (val, &crty.sty, &rty.sty) {
             // the easy case, deref a reference
             (ConstValue::Scalar(Scalar::Ptr(p)), x, y) if x == y => ConstValue::ByRef(
-                p.alloc_id,
+                p,
                 self.tcx.alloc_map.lock().unwrap_memory(p.alloc_id),
-                p.offset,
             ),
             // unsize array to slice if pattern is array but match value or other patterns are slice
             (ConstValue::Scalar(Scalar::Ptr(p)), ty::Array(t, n), ty::Slice(u)) => {
@@ -1428,15 +1427,14 @@ fn slice_pat_covered_by_const<'tcx>(
     suffix: &[Pattern<'tcx>]
 ) -> Result<bool, ErrorReported> {
     let data: &[u8] = match (const_val.val, &const_val.ty.sty) {
-        (ConstValue::ByRef(id, alloc, offset), ty::Array(t, n)) => {
+        (ConstValue::ByRef(ptr, alloc), ty::Array(t, n)) => {
             if *t != tcx.types.u8 {
                 // FIXME(oli-obk): can't mix const patterns with slice patterns and get
                 // any sort of exhaustiveness/unreachable check yet
                 // This solely means that we don't lint about unreachable patterns, even if some
                 // are definitely unreachable.
                 return Ok(false);
             }
-            let ptr = Pointer::new(id, offset);
             let n = n.assert_usize(tcx).unwrap();
             alloc.get_bytes(&tcx, ptr, Size::from_bytes(n)).unwrap()
         },
@@ -1778,8 +1776,8 @@ fn specialize<'p, 'a: 'p, 'tcx: 'a>(
                     let (opt_ptr, n, ty) = match value.ty.sty {
                         ty::TyKind::Array(t, n) => {
                             match value.val {
-                                ConstValue::ByRef(id, alloc, offset) => (
-                                    Some((Pointer::new(id, offset), alloc)),
+                                ConstValue::ByRef(ptr, alloc) => (
+                                    Some((ptr, alloc)),
                                     n.unwrap_usize(cx.tcx),
                                     t,
                                 ),

src/librustc_mir/interpret/operand.rs

@@ -12,7 +12,7 @@ use rustc::mir::interpret::{
     EvalResult, EvalErrorKind,
 };
 use super::{
-    EvalContext, Machine, AllocMap, Allocation, AllocationExtra,
+    EvalContext, Machine,
     MemPlace, MPlaceTy, PlaceTy, Place, MemoryKind,
 };
 pub use rustc::mir::interpret::ScalarMaybeUndef;
@@ -269,7 +269,7 @@ pub(super) fn from_known_layout<'tcx>(
 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
     /// Try reading an immediate in memory; this is interesting particularly for ScalarPair.
     /// Returns `None` if the layout does not permit loading this as a value.
-    pub(super) fn try_read_immediate_from_mplace(
+    fn try_read_immediate_from_mplace(
         &self,
         mplace: MPlaceTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx, Option<Immediate<M::PointerTag>>> {
@@ -323,7 +323,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
     /// Note that for a given layout, this operation will either always fail or always
     /// succeed!  Whether it succeeds depends on whether the layout can be represented
     /// in a `Immediate`, not on which data is stored there currently.
-    pub(crate) fn try_read_immediate(
+    pub(super) fn try_read_immediate(
         &self,
         src: OpTy<'tcx, M::PointerTag>,
     ) -> EvalResult<'tcx, Result<Immediate<M::PointerTag>, MemPlace<M::PointerTag>>> {
@@ -508,7 +508,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
 
     // Evaluate a place with the goal of reading from it.  This lets us sometimes
     // avoid allocations.
-    fn eval_place_to_op(
+    pub(super) fn eval_place_to_op(
         &self,
         mir_place: &mir::Place<'tcx>,
         layout: Option<TyLayout<'tcx>>,
@@ -545,14 +545,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             Move(ref place) =>
                 self.eval_place_to_op(place, layout)?,
 
-            Constant(ref constant) => {
-                let layout = from_known_layout(layout, || {
-                    let ty = self.monomorphize(mir_op.ty(self.mir(), *self.tcx))?;
-                    self.layout_of(ty)
-                })?;
-                let op = self.const_value_to_op(*constant.literal)?;
-                OpTy { op, layout }
-            }
+            Constant(ref constant) => self.lazy_const_to_op(*constant.literal, layout)?,
         };
         trace!("{:?}: {:?}", mir_op, *op);
         Ok(op)
@@ -568,38 +561,55 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             .collect()
     }
 
-    // Used when Miri runs into a constant, and (indirectly through lazy_const_to_op) by CTFE.
-    fn const_value_to_op(
+    // Used when Miri runs into a constant, and by CTFE.
+    pub fn lazy_const_to_op(
         &self,
         val: ty::LazyConst<'tcx>,
-    ) -> EvalResult<'tcx, Operand<M::PointerTag>> {
-        trace!("const_value_to_op: {:?}", val);
-        let val = match val {
+        layout: Option<TyLayout<'tcx>>,
+    ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        trace!("const_to_op: {:?}", val);
+        match val {
             ty::LazyConst::Unevaluated(def_id, substs) => {
                 let instance = self.resolve(def_id, substs)?;
-                return Ok(*OpTy::from(self.const_eval_raw(GlobalId {
+                return Ok(OpTy::from(self.const_eval_raw(GlobalId {
                     instance,
                     promoted: None,
                 })?));
             },
-            ty::LazyConst::Evaluated(c) => c,
-        };
-        match val.val {
-            ConstValue::ByRef(id, alloc, offset) => {
+            ty::LazyConst::Evaluated(c) => self.const_to_op(c, layout),
+        }
+    }
+
+    // Used when Miri runs into a constant, and (indirectly through lazy_const_to_op) by CTFE.
+    pub fn const_to_op(
+        &self,
+        val: ty::Const<'tcx>,
+        layout: Option<TyLayout<'tcx>>,
+    ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> {
+        let layout = from_known_layout(layout, || {
+            let ty = self.monomorphize(val.ty)?;
+            self.layout_of(ty)
+        })?;
+        let op = match val.val {
+            ConstValue::ByRef(ptr, alloc) => {
                 // We rely on mutability being set correctly in that allocation to prevent writes
                 // where none should happen -- and for `static mut`, we copy on demand anyway.
-                Ok(Operand::Indirect(
-                    MemPlace::from_ptr(Pointer::new(id, offset), alloc.align)
-                ).with_default_tag())
+                Operand::Indirect(
+                    MemPlace::from_ptr(ptr, alloc.align)
+                ).with_default_tag()
             },
             ConstValue::Slice(a, b) =>
-                Ok(Operand::Immediate(Immediate::ScalarPair(
+                Operand::Immediate(Immediate::ScalarPair(
                     a.into(),
                     Scalar::from_uint(b, self.tcx.data_layout.pointer_size).into(),
-                )).with_default_tag()),
+                )).with_default_tag(),
             ConstValue::Scalar(x) =>
-                Ok(Operand::Immediate(Immediate::Scalar(x.into())).with_default_tag()),
-        }
+                Operand::Immediate(Immediate::Scalar(x.into())).with_default_tag(),
+        };
+        Ok(OpTy {
+            op,
+            layout,
+        })
     }
 
     /// Read discriminant, return the runtime value as well as the variant index.
@@ -699,23 +709,4 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             }
         })
     }
-
-}
-
-impl<'a, 'mir, 'tcx, M> EvalContext<'a, 'mir, 'tcx, M>
-where
-    M: Machine<'a, 'mir, 'tcx, PointerTag=()>,
-    // FIXME: Working around https://github.com/rust-lang/rust/issues/24159
-    M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<(), M::AllocExtra>)>,
-    M::AllocExtra: AllocationExtra<(), M::MemoryExtra>,
-{
-    // FIXME: CTFE should use allocations, then we can remove this.
-    pub(crate) fn lazy_const_to_op(
-        &self,
-        cnst: ty::LazyConst<'tcx>,
-        ty: ty::Ty<'tcx>,
-    ) -> EvalResult<'tcx, OpTy<'tcx>> {
-        let op = self.const_value_to_op(cnst)?;
-        Ok(OpTy { op, layout: self.layout_of(ty)? })
-    }
 }

src/librustc_mir/interpret/step.rs

@@ -266,8 +266,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M>
             }
 
             Discriminant(ref place) => {
-                let place = self.eval_place(place)?;
-                let discr_val = self.read_discriminant(self.place_to_op(place)?)?.0;
+                let op = self.eval_place_to_op(place, None)?;
+                let discr_val = self.read_discriminant(op)?.0;
                 let size = dest.layout.size;
                 self.write_scalar(Scalar::from_uint(discr_val, size), dest)?;
             }

src/librustc_mir/monomorphize/collector.rs

@@ -1257,7 +1257,7 @@ fn collect_const<'a, 'tcx>(
         ConstValue::Slice(Scalar::Ptr(ptr), _) |
         ConstValue::Scalar(Scalar::Ptr(ptr)) =>
             collect_miri(tcx, ptr.alloc_id, output),
-        ConstValue::ByRef(_id, alloc, _offset) => {
+        ConstValue::ByRef(_ptr, alloc) => {
             for &((), id) in alloc.relocations.values() {
                 collect_miri(tcx, id, output);
             }

src/librustc_mir/transform/const_prop.rs

@@ -253,7 +253,7 @@ impl<'a, 'mir, 'tcx> ConstPropagator<'a, 'mir, 'tcx> {
         source_info: SourceInfo,
     ) -> Option<Const<'tcx>> {
         self.ecx.tcx.span = source_info.span;
-        match self.ecx.lazy_const_to_op(*c.literal, c.ty) {
+        match self.ecx.lazy_const_to_op(*c.literal, None) {
             Ok(op) => {
                 Some((op, c.span))
             },

src/librustc_typeck/check/mod.rs

@@ -1464,7 +1464,7 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt, id: DefId, span: Span) {
     };
     let param_env = ty::ParamEnv::reveal_all();
     if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
-        let alloc = if let ConstValue::ByRef(_, allocation, _) = static_.val {
+        let alloc = if let ConstValue::ByRef(_, allocation) = static_.val {
             allocation
         } else {
             bug!("Matching on non-ByRef static")