Introduce `ConstAllocation`.

Currently some `Allocation`s are interned, some are not, and it's very
hard to tell at a use point which is which.

This commit introduces `ConstAllocation` for the known-interned ones,
which makes the division much clearer. `ConstAllocation::inner()` is
used to get the underlying `Allocation`.

In some places it's natural to use an `Allocation`, in some it's natural
to use a `ConstAllocation`, and in some places there's no clear choice.
I've tried to make things look as nice as possible, while generally
favouring `ConstAllocation`, which is the type that embodies more
information. This does require quite a few calls to `inner()`.

The commit also tweaks how `PartialOrd` works for `Interned`. The
previous code was too clever by half, building on `T: Ord` to make the
code shorter. That caused problems with deriving `PartialOrd` and `Ord`
for `ConstAllocation`, so I changed it to build on `T: PartialOrd`,
which is slightly more verbose but much more standard and avoided the
problems.

1 files changed, 7 insertions, 6 deletions

diff --git a/compiler/rustc_codegen_gcc/src/common.rs b/compiler/rustc_codegen_gcc/src/common.rs
index 5851826147d..a80b8e5b76c 100644
--- a/compiler/rustc_codegen_gcc/src/common.rs
+++ b/compiler/rustc_codegen_gcc/src/common.rs
@@ -13,7 +13,7 @@ use rustc_codegen_ssa::traits::{
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::ScalarInt;
 use rustc_middle::ty::layout::{TyAndLayout, LayoutOf};
-use rustc_middle::mir::interpret::{Allocation, GlobalAlloc, Scalar};
+use rustc_middle::mir::interpret::{ConstAllocation, GlobalAlloc, Scalar};
 use rustc_span::Symbol;
 use rustc_target::abi::{self, HasDataLayout, Pointer, Size};
 
@@ -230,6 +230,7 @@ impl<'gcc, 'tcx> ConstMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
                     match self.tcx.global_alloc(alloc_id) {
                         GlobalAlloc::Memory(alloc) => {
                             let init = const_alloc_to_gcc(self, alloc);
+                            let alloc = alloc.inner();
                             let value =
                                 match alloc.mutability {
                                     Mutability::Mut => self.static_addr_of_mut(init, alloc.align, None),
@@ -262,21 +263,21 @@ impl<'gcc, 'tcx> ConstMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         }
     }
 
-    fn const_data_from_alloc(&self, alloc: &Allocation) -> Self::Value {
+    fn const_data_from_alloc(&self, alloc: ConstAllocation<'tcx>) -> Self::Value {
         const_alloc_to_gcc(self, alloc)
     }
 
-    fn from_const_alloc(&self, layout: TyAndLayout<'tcx>, alloc: &Allocation, offset: Size) -> PlaceRef<'tcx, RValue<'gcc>> {
-        assert_eq!(alloc.align, layout.align.abi);
+    fn from_const_alloc(&self, layout: TyAndLayout<'tcx>, alloc: ConstAllocation<'tcx>, offset: Size) -> PlaceRef<'tcx, RValue<'gcc>> {
+        assert_eq!(alloc.inner().align, layout.align.abi);
         let ty = self.type_ptr_to(layout.gcc_type(self, true));
         let value =
             if layout.size == Size::ZERO {
-                let value = self.const_usize(alloc.align.bytes());
+                let value = self.const_usize(alloc.inner().align.bytes());
                 self.context.new_cast(None, value, ty)
             }
             else {
                 let init = const_alloc_to_gcc(self, alloc);
-                let base_addr = self.static_addr_of(init, alloc.align, None);
+                let base_addr = self.static_addr_of(init, alloc.inner().align, None);
 
                 let array = self.const_bitcast(base_addr, self.type_i8p());
                 let value = self.context.new_array_access(None, array, self.const_usize(offset.bytes())).get_address(None);