Rollup merge of rust-lang#63914 - hvenev:repr-fields, r=eddyb

ty: use Align for ReprOptions pack and align.

Author: Centril

src/librustc/ty/layout.rs

@@ -273,14 +273,12 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                              repr: &ReprOptions,
                              kind: StructKind) -> Result<LayoutDetails, LayoutError<'tcx>> {
         let dl = self.data_layout();
-        let packed = repr.packed();
-        if packed && repr.align > 0 {
+        let pack = repr.pack;
+        if pack.is_some() && repr.align.is_some() {
             bug!("struct cannot be packed and aligned");
         }
 
-        let pack = Align::from_bytes(repr.pack as u64).unwrap();
-
-        let mut align = if packed {
+        let mut align = if pack.is_some() {
             dl.i8_align
         } else {
             dl.aggregate_align
@@ -303,7 +301,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
             };
             let optimizing = &mut inverse_memory_index[..end];
             let field_align = |f: &TyLayout<'_>| {
-                if packed { f.align.abi.min(pack) } else { f.align.abi }
+                if let Some(pack) = pack { f.align.abi.min(pack) } else { f.align.abi }
             };
             match kind {
                 StructKind::AlwaysSized |
@@ -334,7 +332,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         let mut largest_niche_available = 0;
 
         if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
-            let prefix_align = if packed {
+            let prefix_align = if let Some(pack) = pack {
                 prefix_align.min(pack)
             } else {
                 prefix_align
@@ -355,7 +353,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
             }
 
             // Invariant: offset < dl.obj_size_bound() <= 1<<61
-            let field_align = if packed {
+            let field_align = if let Some(pack) = pack {
                 field.align.min(AbiAndPrefAlign::new(pack))
             } else {
                 field.align
@@ -379,10 +377,8 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                 .ok_or(LayoutError::SizeOverflow(ty))?;
         }
 
-        if repr.align > 0 {
-            let repr_align = repr.align as u64;
-            align = align.max(AbiAndPrefAlign::new(Align::from_bytes(repr_align).unwrap()));
-            debug!("univariant repr_align: {:?}", repr_align);
+        if let Some(repr_align) = repr.align {
+            align = align.max(AbiAndPrefAlign::new(repr_align));
         }
 
         debug!("univariant min_size: {:?}", offset);
@@ -730,23 +726,18 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                 }).collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
 
                 if def.is_union() {
-                    let packed = def.repr.packed();
-                    if packed && def.repr.align > 0 {
-                        bug!("Union cannot be packed and aligned");
+                    if def.repr.pack.is_some() && def.repr.align.is_some() {
+                        bug!("union cannot be packed and aligned");
                     }
 
-                    let pack = Align::from_bytes(def.repr.pack as u64).unwrap();
-
-                    let mut align = if packed {
+                    let mut align = if def.repr.pack.is_some() {
                         dl.i8_align
                     } else {
                         dl.aggregate_align
                     };
 
-                    if def.repr.align > 0 {
-                        let repr_align = def.repr.align as u64;
-                        align = align.max(
-                            AbiAndPrefAlign::new(Align::from_bytes(repr_align).unwrap()));
+                    if let Some(repr_align) = def.repr.align {
+                        align = align.max(AbiAndPrefAlign::new(repr_align));
                     }
 
                     let optimize = !def.repr.inhibit_union_abi_opt();
@@ -755,13 +746,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     let index = VariantIdx::new(0);
                     for field in &variants[index] {
                         assert!(!field.is_unsized());
-
-                        let field_align = if packed {
-                            field.align.min(AbiAndPrefAlign::new(pack))
-                        } else {
-                            field.align
-                        };
-                        align = align.max(field_align);
+                        align = align.max(field.align);
 
                         // If all non-ZST fields have the same ABI, forward this ABI
                         if optimize && !field.is_zst() {
@@ -796,6 +781,10 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                         size = cmp::max(size, field.size);
                     }
 
+                    if let Some(pack) = def.repr.pack {
+                        align = align.min(AbiAndPrefAlign::new(pack));
+                    }
+
                     return Ok(tcx.intern_layout(LayoutDetails {
                         variants: Variants::Single { index },
                         fields: FieldPlacement::Union(variants[index].len()),
@@ -1637,7 +1626,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
         };
 
         let adt_kind = adt_def.adt_kind();
-        let adt_packed = adt_def.repr.packed();
+        let adt_packed = adt_def.repr.pack.is_some();
 
         let build_variant_info = |n: Option<Ident>,
                                   flds: &[ast::Name],

src/librustc/ty/mod.rs

@@ -33,6 +33,7 @@ use arena::SyncDroplessArena;
 use crate::session::DataTypeKind;
 
 use rustc_serialize::{self, Encodable, Encoder};
+use rustc_target::abi::Align;
 use std::cell::RefCell;
 use std::cmp::{self, Ordering};
 use std::fmt;
@@ -2057,8 +2058,8 @@ impl_stable_hash_for!(struct ReprFlags {
 #[derive(Copy, Clone, Debug, Eq, PartialEq, RustcEncodable, RustcDecodable, Default)]
 pub struct ReprOptions {
     pub int: Option<attr::IntType>,
-    pub align: u32,
-    pub pack: u32,
+    pub align: Option<Align>,
+    pub pack: Option<Align>,
     pub flags: ReprFlags,
 }
 
@@ -2073,18 +2074,19 @@ impl ReprOptions {
     pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
         let mut flags = ReprFlags::empty();
         let mut size = None;
-        let mut max_align = 0;
-        let mut min_pack = 0;
+        let mut max_align: Option<Align> = None;
+        let mut min_pack: Option<Align> = None;
         for attr in tcx.get_attrs(did).iter() {
             for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
                 flags.insert(match r {
                     attr::ReprC => ReprFlags::IS_C,
                     attr::ReprPacked(pack) => {
-                        min_pack = if min_pack > 0 {
-                            cmp::min(pack, min_pack)
+                        let pack = Align::from_bytes(pack as u64).unwrap();
+                        min_pack = Some(if let Some(min_pack) = min_pack {
+                            min_pack.min(pack)
                         } else {
                             pack
-                        };
+                        });
                         ReprFlags::empty()
                     },
                     attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
@@ -2094,7 +2096,7 @@ impl ReprOptions {
                         ReprFlags::empty()
                     },
                     attr::ReprAlign(align) => {
-                        max_align = cmp::max(align, max_align);
+                        max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
                         ReprFlags::empty()
                     },
                 });
@@ -2113,7 +2115,7 @@ impl ReprOptions {
     #[inline]
     pub fn c(&self) -> bool { self.flags.contains(ReprFlags::IS_C) }
     #[inline]
-    pub fn packed(&self) -> bool { self.pack > 0 }
+    pub fn packed(&self) -> bool { self.pack.is_some() }
     #[inline]
     pub fn transparent(&self) -> bool { self.flags.contains(ReprFlags::IS_TRANSPARENT) }
     #[inline]
@@ -2133,8 +2135,12 @@ impl ReprOptions {
     /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
     /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
     pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
-        self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.pack == 1 ||
-            self.int.is_some()
+        if let Some(pack) = self.pack {
+            if pack.bytes() == 1 {
+                return true;
+            }
+        }
+        self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
     }
 
     /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.

src/librustc_typeck/check/mod.rs

@@ -1859,14 +1859,18 @@ fn check_packed(tcx: TyCtxt<'_>, sp: Span, def_id: DefId) {
         for attr in tcx.get_attrs(def_id).iter() {
             for r in attr::find_repr_attrs(&tcx.sess.parse_sess, attr) {
                 if let attr::ReprPacked(pack) = r {
-                    if pack != repr.pack {
-                        struct_span_err!(tcx.sess, sp, E0634,
-                                         "type has conflicting packed representation hints").emit();
+                    if let Some(repr_pack) = repr.pack {
+                        if pack as u64 != repr_pack.bytes() {
+                            struct_span_err!(
+                                tcx.sess, sp, E0634,
+                                "type has conflicting packed representation hints"
+                            ).emit();
+                        }
                     }
                 }
             }
         }
-        if repr.align > 0 {
+        if repr.align.is_some() {
             struct_span_err!(tcx.sess, sp, E0587,
                              "type has conflicting packed and align representation hints").emit();
         }
@@ -1885,7 +1889,7 @@ fn check_packed_inner(tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec<DefId>) ->
     }
     if let ty::Adt(def, substs) = t.sty {
         if def.is_struct() || def.is_union() {
-            if tcx.adt_def(def.did).repr.align > 0 {
+            if tcx.adt_def(def.did).repr.align.is_some() {
                 return true;
             }
             // push struct def_id before checking fields