compiler: Parse p- specs in datalayout string, allow definition of custom default data address space

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -443,7 +443,7 @@ fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut Constant
             let addend = {
                 let endianness = tcx.data_layout.endian;
                 let offset = offset.bytes() as usize;
-                let ptr_size = tcx.data_layout.pointer_size;
+                let ptr_size = tcx.data_layout.pointer_size();
                 let bytes = &alloc.inspect_with_uninit_and_ptr_outside_interpreter(
                     offset..offset + ptr_size.bytes() as usize,
                 );