Correctly align all allocs

Fixes rust-lang#348

Author: bjorn3

build_sysroot/Cargo.toml

@@ -17,7 +17,3 @@ rustc-std-workspace-alloc = { path = "./rustc-std-workspace-alloc" }
 
 [profile.release]
 debug = true
-
-[profile.dev]
-# FIXME correctly align constants, so that copy_nonoverlapping doesn't complain about alignment
-debug-assertions = false

example/mini_core.rs

@@ -186,6 +186,21 @@ impl Sub for i16 {
     }
 }
 
+#[lang = "rem"]
+pub trait Rem<RHS = Self> {
+    type Output;
+
+    fn rem(self, rhs: RHS) -> Self::Output;
+}
+
+impl Rem for usize {
+    type Output = Self;
+
+    fn rem(self, rhs: Self) -> Self {
+        self % rhs
+    }
+}
+
 #[lang = "bitor"]
 pub trait BitOr<RHS = Self> {
     type Output;

example/mini_core_hello_world.rs

@@ -134,6 +134,10 @@ fn main() {
 
     call_return_u128_pair();
 
+    let slice = &[0, 1] as &[i32];
+    let slice_ptr = slice as *const [i32] as *const i32;
+    assert_eq!(slice_ptr as usize % 4, 0);
+
     //return;
 
     unsafe {

src/constant.rs

@@ -3,7 +3,7 @@ use std::borrow::Cow;
 use rustc::mir::interpret::{
     read_target_uint, AllocId, GlobalAlloc, Allocation, ConstValue, InterpResult, GlobalId, Scalar,
 };
-use rustc::ty::Const;
+use rustc::ty::{Const, layout::Align};
 use rustc_mir::interpret::{
     InterpCx, ImmTy, Machine, Memory, MemoryKind, OpTy, PlaceTy,
     StackPopCleanup,
@@ -170,13 +170,13 @@ fn trans_const_place<'a, 'tcx: 'a>(
     //println!("const value: {:?} allocation: {:?}", value, alloc);
     let alloc_id = fx.tcx.alloc_map.lock().create_memory_alloc(alloc);
     fx.constants.todo.insert(TodoItem::Alloc(alloc_id));
-    let data_id = data_id_for_alloc_id(fx.module, alloc_id);
+    let data_id = data_id_for_alloc_id(fx.module, alloc_id, alloc.align);
     cplace_for_dataid(fx, const_.ty, data_id)
 }
 
-fn data_id_for_alloc_id(module: &mut Module<impl Backend>, alloc_id: AllocId) -> DataId {
+fn data_id_for_alloc_id<B: Backend>(module: &mut Module<B>, alloc_id: AllocId, align: Align) -> DataId {
     module
-        .declare_data(&format!("__alloc_{}", alloc_id.0), Linkage::Local, false, None)
+        .declare_data(&format!("__alloc_{}", alloc_id.0), Linkage::Local, false, Some(align.bytes() as u8))
         .unwrap()
 }
 
@@ -245,8 +245,8 @@ fn define_all_allocs(
         let (data_id, alloc) = match todo_item {
             TodoItem::Alloc(alloc_id) => {
                 //println!("alloc_id {}", alloc_id);
-                let data_id = data_id_for_alloc_id(module, alloc_id);
                 let alloc = memory.get(alloc_id).unwrap();
+                let data_id = data_id_for_alloc_id(module, alloc_id, alloc.align);
                 (data_id, alloc)
             }
             TodoItem::Static(def_id) => {
@@ -302,7 +302,7 @@ fn define_all_allocs(
                 }
                 GlobalAlloc::Memory(_) => {
                     cx.todo.insert(TodoItem::Alloc(reloc));
-                    data_id_for_alloc_id(module, reloc)
+                    data_id_for_alloc_id(module, reloc, alloc.align)
                 }
                 GlobalAlloc::Static(def_id) => {
                     cx.todo.insert(TodoItem::Static(def_id));