CTFE core engine allocation & memory API improvemenets

- make Allocation API offset-based (no more Pointer)
- make Memory API higher-level (combine checking for access and getting access into one operation)

src/constant.rs

@@ -6,7 +6,7 @@
 use rustc_errors::ErrorReported;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::mir::interpret::{
-    read_target_uint, AllocId, Allocation, ConstValue, ErrorHandled, GlobalAlloc, Pointer, Scalar,
+    alloc_range, read_target_uint, AllocId, Allocation, ConstValue, ErrorHandled, GlobalAlloc, Scalar,
 };
 use rustc_middle::ty::ConstKind;
 
@@ -176,8 +176,7 @@ pub(crate) fn codegen_const_value<'tcx>(
                     std::iter::repeat(0).take(size.bytes_usize()).collect::<Vec<u8>>(),
                     align,
                 );
-                let ptr = Pointer::new(AllocId(!0), Size::ZERO); // The alloc id is never used
-                alloc.write_scalar(fx, ptr, x.into(), size).unwrap();
+                alloc.write_scalar(fx, alloc_range(Size::ZERO, size), x.into()).unwrap();
                 let alloc = fx.tcx.intern_const_alloc(alloc);
                 return CValue::by_ref(pointer_for_allocation(fx, alloc), layout);
             }

src/intrinsics/simd.rs

@@ -86,9 +86,8 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
 
                 let idx_bytes = match idx_const {
                     ConstValue::ByRef { alloc, offset } => {
-                        let ptr = Pointer::new(AllocId(0 /* dummy */), offset);
                         let size = Size::from_bytes(4 * ret_lane_count /* size_of([u32; ret_lane_count]) */);
-                        alloc.get_bytes(fx, ptr, size).unwrap()
+                        alloc.get_bytes(fx, alloc_range(offset, size)).unwrap()
                     }
                     _ => unreachable!("{:?}", idx_const),
                 };