Add a pointer to address cast kind

A pointer to address cast are often special-cased.
Introduce a dedicated cast kind to make them easy distinguishable.

3 files changed, 30 insertions, 36 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index be34a77bdba..af563c1450e 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -1,3 +1,4 @@
+use std::assert_matches::assert_matches;
 use std::convert::TryFrom;
 
 use rustc_apfloat::ieee::{Double, Single};
@@ -30,6 +31,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.unsize_into(src, cast_ty, dest)?;
             }
 
+            PointerAddress => {
+                let src = self.read_immediate(src)?;
+                let res = self.pointer_address_cast(&src, cast_ty)?;
+                self.write_immediate(res, dest)?;
+            }
+
             Misc => {
                 let src = self.read_immediate(src)?;
                 let res = self.misc_cast(&src, cast_ty)?;
@@ -174,23 +181,23 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         // # The remaining source values are scalar and "int-like".
         let scalar = src.to_scalar()?;
+        Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into())
+    }
 
-        // If we are casting from a pointer to something
-        // that is not a pointer, mark the pointer as exposed
-        if src.layout.ty.is_any_ptr() && !cast_ty.is_any_ptr() {
-            let ptr = self.scalar_to_ptr(scalar)?;
-
-            match ptr.into_pointer_or_addr() {
-                Ok(ptr) => {
-                    M::expose_ptr(self, ptr)?;
-                }
-                Err(_) => {
-                    // do nothing, exposing an invalid pointer
-                    // has no meaning
-                }
-            };
-        }
+    pub fn pointer_address_cast(
+        &mut self,
+        src: &ImmTy<'tcx, M::PointerTag>,
+        cast_ty: Ty<'tcx>,
+    ) -> InterpResult<'tcx, Immediate<M::PointerTag>> {
+        assert_matches!(src.layout.ty.kind(), ty::RawPtr(_) | ty::FnPtr(_));
+        assert!(cast_ty.is_integral());
 
+        let scalar = src.to_scalar()?;
+        let ptr = self.scalar_to_ptr(scalar)?;
+        match ptr.into_pointer_or_addr() {
+            Ok(ptr) => M::expose_ptr(self, ptr)?,
+            Err(_) => {} // do nothing, exposing an invalid pointer has no meaning
+        };
         Ok(self.cast_from_int_like(scalar, src.layout, cast_ty)?.into())
     }
 
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
index eea6e2a47a9..4ef33d62a6b 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -8,7 +8,6 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{ImplSource, Obligation, ObligationCause};
 use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
-use rustc_middle::ty::cast::CastTy;
 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
 use rustc_middle::ty::{self, adjustment::PointerCast, Instance, InstanceDef, Ty, TyCtxt};
 use rustc_middle::ty::{Binder, TraitPredicate, TraitRef, TypeFoldable};
@@ -543,16 +542,12 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 // in the type of any local, which also excludes casts).
             }
 
-            Rvalue::Cast(CastKind::Misc, ref operand, cast_ty) => {
-                let operand_ty = operand.ty(self.body, self.tcx);
-                let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
-                let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
-
-                if let (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) = (cast_in, cast_out) {
-                    self.check_op(ops::RawPtrToIntCast);
-                }
+            Rvalue::Cast(CastKind::PointerAddress, _, _) => {
+                self.check_op(ops::RawPtrToIntCast);
             }
 
+            Rvalue::Cast(CastKind::Misc, _, _) => {}
+
             Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => {}
             Rvalue::ShallowInitBox(_, _) => {}
 
diff --git a/compiler/rustc_const_eval/src/transform/promote_consts.rs b/compiler/rustc_const_eval/src/transform/promote_consts.rs
index fc6b8a1a723..ea23bd14d25 100644
--- a/compiler/rustc_const_eval/src/transform/promote_consts.rs
+++ b/compiler/rustc_const_eval/src/transform/promote_consts.rs
@@ -16,7 +16,6 @@ use rustc_hir as hir;
 use rustc_middle::mir::traversal::ReversePostorderIter;
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
-use rustc_middle::ty::cast::CastTy;
 use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::{self, List, TyCtxt, TypeFoldable};
 use rustc_span::Span;
@@ -502,18 +501,11 @@ impl<'tcx> Validator<'_, 'tcx> {
 
             Rvalue::ThreadLocalRef(_) => return Err(Unpromotable),
 
-            Rvalue::Cast(kind, operand, cast_ty) => {
-                if matches!(kind, CastKind::Misc) {
-                    let operand_ty = operand.ty(self.body, self.tcx);
-                    let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
-                    let cast_out = CastTy::from_ty(*cast_ty).expect("bad output type for cast");
-                    if let (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) = (cast_in, cast_out) {
-                        // ptr-to-int casts are not possible in consts and thus not promotable
-                        return Err(Unpromotable);
-                    }
-                    // int-to-ptr casts are fine, they just use the integer value at pointer type.
-                }
+            // ptr-to-int casts are not possible in consts and thus not promotable
+            Rvalue::Cast(CastKind::PointerAddress, _, _) => return Err(Unpromotable),
 
+            // int-to-ptr casts are fine, they just use the integer value at pointer type.
+            Rvalue::Cast(_, operand, _) => {
                 self.validate_operand(operand)?;
             }