Auto merge of #54071 - eddyb:alignsssss, r=oli-obk

rustc_target: separate out an individual alignment quantity type from Align.

Before this PR, `rustc_target::abi::Align` combined "power-of-two alignment quantity" semantics, with a distinction between ABI (required) and preferred alignment (by having two quantities).

After this PR, `Align` is only *one* such quantity, and a new `AbiAndPrefAlign` type is introduced to hold the pair of ABI and preferred `Align` quantities.

`Align` is used everywhere one quantity is necessary/sufficient, simplifying some of the code in codegen/miri, while `AbiAndPrefAlign` only in layout computation (to propagate preferred alignment).

r? @oli-obk cc @nagisa @RalfJung @nikomatsakis

9 files changed, 52 insertions, 57 deletions

diff --git a/src/librustc_codegen_ssa/glue.rs b/src/librustc_codegen_ssa/glue.rs
index 515f36b5c65..bb28ea74dc0 100644
--- a/src/librustc_codegen_ssa/glue.rs
+++ b/src/librustc_codegen_ssa/glue.rs
@@ -25,14 +25,12 @@ pub fn size_and_align_of_dst<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
     t: Ty<'tcx>,
     info: Option<Bx::Value>
 ) -> (Bx::Value, Bx::Value) {
-    debug!("calculate size of DST: {}; with lost info: {:?}",
-           t, info);
-    if bx.cx().type_is_sized(t) {
-        let (size, align) = bx.cx().layout_of(t).size_and_align();
-        debug!("size_and_align_of_dst t={} info={:?} size: {:?} align: {:?}",
-               t, info, size, align);
-        let size = bx.cx().const_usize(size.bytes());
-        let align = bx.cx().const_usize(align.abi());
+    let layout = bx.cx().layout_of(t);
+    debug!("size_and_align_of_dst(ty={}, info={:?}): layout: {:?}",
+           t, info, layout);
+    if !layout.is_unsized() {
+        let size = bx.cx().const_usize(layout.size.bytes());
+        let align = bx.cx().const_usize(layout.align.abi.bytes());
         return (size, align);
     }
     match t.sty {
@@ -42,24 +40,22 @@ pub fn size_and_align_of_dst<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
             (meth::SIZE.get_usize(bx, vtable), meth::ALIGN.get_usize(bx, vtable))
         }
         ty::Slice(_) | ty::Str => {
-            let unit = t.sequence_element_type(bx.tcx());
+            let unit = layout.field(bx.cx(), 0);
             // The info in this case is the length of the str, so the size is that
             // times the unit size.
-            let (size, align) = bx.cx().layout_of(unit).size_and_align();
-            (bx.mul(info.unwrap(), bx.cx().const_usize(size.bytes())),
-             bx.cx().const_usize(align.abi()))
+            (bx.mul(info.unwrap(), bx.cx().const_usize(unit.size.bytes())),
+             bx.cx().const_usize(unit.align.abi.bytes()))
         }
         _ => {
             // First get the size of all statically known fields.
             // Don't use size_of because it also rounds up to alignment, which we
             // want to avoid, as the unsized field's alignment could be smaller.
             assert!(!t.is_simd());
-            let layout = bx.cx().layout_of(t);
             debug!("DST {} layout: {:?}", t, layout);
 
             let i = layout.fields.count() - 1;
             let sized_size = layout.fields.offset(i).bytes();
-            let sized_align = layout.align.abi();
+            let sized_align = layout.align.abi.bytes();
             debug!("DST {} statically sized prefix size: {} align: {}",
                    t, sized_size, sized_align);
             let sized_size = bx.cx().const_usize(sized_size);
diff --git a/src/librustc_codegen_ssa/meth.rs b/src/librustc_codegen_ssa/meth.rs
index 06c4f7a87d8..e45cccee349 100644
--- a/src/librustc_codegen_ssa/meth.rs
+++ b/src/librustc_codegen_ssa/meth.rs
@@ -41,7 +41,7 @@ impl<'a, 'tcx: 'a> VirtualIndex {
             llvtable,
             bx.cx().type_ptr_to(bx.cx().fn_ptr_backend_type(fn_ty))
         );
-        let ptr_align = bx.tcx().data_layout.pointer_align;
+        let ptr_align = bx.tcx().data_layout.pointer_align.abi;
         let gep = bx.inbounds_gep(llvtable, &[bx.cx().const_usize(self.0)]);
         let ptr = bx.load(gep, ptr_align);
         bx.nonnull_metadata(ptr);
@@ -59,7 +59,7 @@ impl<'a, 'tcx: 'a> VirtualIndex {
         debug!("get_int({:?}, {:?})", llvtable, self);
 
         let llvtable = bx.pointercast(llvtable, bx.cx().type_ptr_to(bx.cx().type_isize()));
-        let usize_align = bx.tcx().data_layout.pointer_align;
+        let usize_align = bx.tcx().data_layout.pointer_align.abi;
         let gep = bx.inbounds_gep(llvtable, &[bx.cx().const_usize(self.0)]);
         let ptr = bx.load(gep, usize_align);
         // Vtable loads are invariant
@@ -100,19 +100,19 @@ pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
         })
     });
 
-    let (size, align) = cx.layout_of(ty).size_and_align();
+    let layout = cx.layout_of(ty);
     // /////////////////////////////////////////////////////////////////////////////////////////////
     // If you touch this code, be sure to also make the corresponding changes to
     // `get_vtable` in rust_mir/interpret/traits.rs
     // /////////////////////////////////////////////////////////////////////////////////////////////
     let components: Vec<_> = [
         cx.get_fn(monomorphize::resolve_drop_in_place(cx.tcx(), ty)),
-        cx.const_usize(size.bytes()),
-        cx.const_usize(align.abi())
+        cx.const_usize(layout.size.bytes()),
+        cx.const_usize(layout.align.abi.bytes())
     ].iter().cloned().chain(methods).collect();
 
     let vtable_const = cx.const_struct(&components, false);
-    let align = cx.data_layout().pointer_align;
+    let align = cx.data_layout().pointer_align.abi;
     let vtable = cx.static_addr_of(vtable_const, align, Some("vtable"));
 
     cx.create_vtable_metadata(ty, vtable);
diff --git a/src/librustc_codegen_ssa/mir/block.rs b/src/librustc_codegen_ssa/mir/block.rs
index 1702ad19b76..75a6f07124a 100644
--- a/src/librustc_codegen_ssa/mir/block.rs
+++ b/src/librustc_codegen_ssa/mir/block.rs
@@ -280,7 +280,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                 scratch.llval
                             }
                             Ref(llval, _, align) => {
-                                assert_eq!(align.abi(), op.layout.align.abi(),
+                                assert_eq!(align, op.layout.align.abi,
                                            "return place is unaligned!");
                                 llval
                             }
@@ -288,7 +288,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let addr = bx.pointercast(llslot, bx.cx().type_ptr_to(
                             bx.cx().cast_backend_type(&cast_ty)
                         ));
-                        bx.load(addr, self.fn_ty.ret.layout.align)
+                        bx.load(addr, self.fn_ty.ret.layout.align.abi)
                     }
                 };
                 bx.ret(llval);
@@ -386,9 +386,9 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let filename = bx.cx().const_str_slice(filename);
                 let line = bx.cx().const_u32(loc.line as u32);
                 let col = bx.cx().const_u32(loc.col.to_usize() as u32 + 1);
-                let align = tcx.data_layout.aggregate_align
-                    .max(tcx.data_layout.i32_align)
-                    .max(tcx.data_layout.pointer_align);
+                let align = tcx.data_layout.aggregate_align.abi
+                    .max(tcx.data_layout.i32_align.abi)
+                    .max(tcx.data_layout.pointer_align.abi);
 
                 // Put together the arguments to the panic entry point.
                 let (lang_item, args) = match *msg {
@@ -522,9 +522,9 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     let filename = bx.cx().const_str_slice(filename);
                     let line = bx.cx().const_u32(loc.line as u32);
                     let col = bx.cx().const_u32(loc.col.to_usize() as u32 + 1);
-                    let align = tcx.data_layout.aggregate_align
-                        .max(tcx.data_layout.i32_align)
-                        .max(tcx.data_layout.pointer_align);
+                    let align = tcx.data_layout.aggregate_align.abi
+                        .max(tcx.data_layout.i32_align.abi)
+                        .max(tcx.data_layout.pointer_align.abi);
 
                     let str = format!(
                         "Attempted to instantiate uninhabited type {} using mem::{}",
@@ -800,12 +800,12 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         (scratch.llval, scratch.align, true)
                     }
                     _ => {
-                        (op.immediate_or_packed_pair(bx), arg.layout.align, false)
+                        (op.immediate_or_packed_pair(bx), arg.layout.align.abi, false)
                     }
                 }
             }
             Ref(llval, _, align) => {
-                if arg.is_indirect() && align.abi() < arg.layout.align.abi() {
+                if arg.is_indirect() && align < arg.layout.align.abi {
                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
                     // have scary latent bugs around.
@@ -826,7 +826,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let addr = bx.pointercast(llval, bx.cx().type_ptr_to(
                     bx.cx().cast_backend_type(&ty))
                 );
-                llval = bx.load(addr, align.min(arg.layout.align));
+                llval = bx.load(addr, align.min(arg.layout.align.abi));
             } else {
                 // We can't use `PlaceRef::load` here because the argument
                 // may have a type we don't treat as immediate, but the ABI
@@ -1006,7 +1006,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             self.codegen_place(bx, dest)
         };
         if fn_ret.is_indirect() {
-            if dest.align.abi() < dest.layout.align.abi() {
+            if dest.align < dest.layout.align.abi {
                 // Currently, MIR code generation does not create calls
                 // that store directly to fields of packed structs (in
                 // fact, the calls it creates write only to temps),
@@ -1062,7 +1062,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let src = self.codegen_operand(bx, src);
         let llty = bx.cx().backend_type(src.layout);
         let cast_ptr = bx.pointercast(dst.llval, bx.cx().type_ptr_to(llty));
-        let align = src.layout.align.min(dst.layout.align);
+        let align = src.layout.align.abi.min(dst.align);
         src.val.store(bx, PlaceRef::new_sized(cast_ptr, src.layout, align));
     }
 
diff --git a/src/librustc_codegen_ssa/mir/mod.rs b/src/librustc_codegen_ssa/mir/mod.rs
index 0579afe1d49..fdc9a37a9eb 100644
--- a/src/librustc_codegen_ssa/mir/mod.rs
+++ b/src/librustc_codegen_ssa/mir/mod.rs
@@ -304,7 +304,7 @@ pub fn codegen_mir<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
                 if local == mir::RETURN_PLACE && fx.fn_ty.ret.is_indirect() {
                     debug!("alloc: {:?} (return place) -> place", local);
                     let llretptr = fx.cx.get_param(llfn, 0);
-                    LocalRef::Place(PlaceRef::new_sized(llretptr, layout, layout.align))
+                    LocalRef::Place(PlaceRef::new_sized(llretptr, layout, layout.align.abi))
                 } else if memory_locals.contains(local) {
                     debug!("alloc: {:?} -> place", local);
                     if layout.is_unsized() {
@@ -555,7 +555,7 @@ fn arg_local_refs<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
             let llarg = bx.cx().get_param(bx.llfn(), llarg_idx as c_uint);
             bx.set_value_name(llarg, &name);
             llarg_idx += 1;
-            PlaceRef::new_sized(llarg, arg.layout, arg.layout.align)
+            PlaceRef::new_sized(llarg, arg.layout, arg.layout.align.abi)
         } else if arg.is_unsized_indirect() {
             // As the storage for the indirect argument lives during
             // the whole function call, we just copy the fat pointer.
diff --git a/src/librustc_codegen_ssa/mir/operand.rs b/src/librustc_codegen_ssa/mir/operand.rs
index d574d89d67e..f6917906d4a 100644
--- a/src/librustc_codegen_ssa/mir/operand.rs
+++ b/src/librustc_codegen_ssa/mir/operand.rs
@@ -152,7 +152,7 @@ impl<'a, 'tcx: 'a, V: CodegenObject> OperandRef<'tcx, V> {
             llval: llptr,
             llextra,
             layout,
-            align: layout.align,
+            align: layout.align.abi,
         }
     }
 
@@ -228,7 +228,7 @@ impl<'a, 'tcx: 'a, V: CodegenObject> OperandRef<'tcx, V> {
                     OperandValue::Immediate(a_llval)
                 } else {
                     assert_eq!(offset, a.value.size(bx.cx())
-                        .abi_align(b.value.align(bx.cx())));
+                        .align_to(b.value.align(bx.cx()).abi));
                     assert_eq!(field.size, b.value.size(bx.cx()));
                     OperandValue::Immediate(b_llval)
                 }
@@ -348,8 +348,8 @@ impl<'a, 'tcx: 'a, V: CodegenObject> OperandValue<V> {
             };
 
         // FIXME: choose an appropriate alignment, or use dynamic align somehow
-        let max_align = Align::from_bits(128, 128).unwrap();
-        let min_align = Align::from_bits(8, 8).unwrap();
+        let max_align = Align::from_bits(128).unwrap();
+        let min_align = Align::from_bits(8).unwrap();
 
         // Allocate an appropriate region on the stack, and copy the value into it
         let (llsize, _) = glue::size_and_align_of_dst(bx, unsized_ty, Some(llextra));
@@ -470,7 +470,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         bx.load_operand(PlaceRef::new_sized(
                             bx.cx().const_undef(bx.cx().type_ptr_to(bx.cx().backend_type(layout))),
                             layout,
-                            layout.align,
+                            layout.align.abi,
                         ))
                     })
             }
diff --git a/src/librustc_codegen_ssa/mir/place.rs b/src/librustc_codegen_ssa/mir/place.rs
index 5b36ee8fd18..e6fd6dfca73 100644
--- a/src/librustc_codegen_ssa/mir/place.rs
+++ b/src/librustc_codegen_ssa/mir/place.rs
@@ -58,8 +58,8 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
     ) -> Self {
         debug!("alloca({:?}: {:?})", name, layout);
         assert!(!layout.is_unsized(), "tried to statically allocate unsized place");
-        let tmp = bx.alloca(bx.cx().backend_type(layout), name, layout.align);
-        Self::new_sized(tmp, layout, layout.align)
+        let tmp = bx.alloca(bx.cx().backend_type(layout), name, layout.align.abi);
+        Self::new_sized(tmp, layout, layout.align.abi)
     }
 
     /// Returns a place for an indirect reference to an unsized place.
@@ -109,7 +109,7 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
                 self.llval
             } else if let layout::Abi::ScalarPair(ref a, ref b) = self.layout.abi {
                 // Offsets have to match either first or second field.
-                assert_eq!(offset, a.value.size(bx.cx()).abi_align(b.value.align(bx.cx())));
+                assert_eq!(offset, a.value.size(bx.cx()).align_to(b.value.align(bx.cx()).abi));
                 bx.struct_gep(self.llval, 1)
             } else {
                 bx.struct_gep(self.llval, bx.cx().backend_field_index(self.layout, ix))
@@ -143,7 +143,7 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
                 if def.repr.packed() {
                     // FIXME(eddyb) generalize the adjustment when we
                     // start supporting packing to larger alignments.
-                    assert_eq!(self.layout.align.abi(), 1);
+                    assert_eq!(self.layout.align.abi.bytes(), 1);
                     return simple();
                 }
             }
@@ -308,9 +308,8 @@ impl<'a, 'tcx: 'a, V: CodegenObject> PlaceRef<'tcx, V> {
                         // Issue #34427: As workaround for LLVM bug on ARM,
                         // use memset of 0 before assigning niche value.
                         let fill_byte = bx.cx().const_u8(0);
-                        let (size, align) = self.layout.size_and_align();
-                        let size = bx.cx().const_usize(size.bytes());
-                        bx.memset(self.llval, fill_byte, size, align, MemFlags::empty());
+                        let size = bx.cx().const_usize(self.layout.size.bytes());
+                        bx.memset(self.llval, fill_byte, size, self.align, MemFlags::empty());
                     }
 
                     let niche = self.project_field(bx, 0);
@@ -419,13 +418,13 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let llval = bx.cx().const_undef(
                             bx.cx().type_ptr_to(bx.cx().backend_type(layout))
                         );
-                        PlaceRef::new_sized(llval, layout, layout.align)
+                        PlaceRef::new_sized(llval, layout, layout.align.abi)
                     }
                 }
             }
             mir::Place::Static(box mir::Static { def_id, ty }) => {
                 let layout = cx.layout_of(self.monomorphize(&ty));
-                PlaceRef::new_sized(cx.get_static(def_id), layout, layout.align)
+                PlaceRef::new_sized(cx.get_static(def_id), layout, layout.align.abi)
             },
             mir::Place::Projection(box mir::Projection {
                 ref base,
diff --git a/src/librustc_codegen_ssa/mir/rvalue.rs b/src/librustc_codegen_ssa/mir/rvalue.rs
index 6b1efa060fd..805c1a343d0 100644
--- a/src/librustc_codegen_ssa/mir/rvalue.rs
+++ b/src/librustc_codegen_ssa/mir/rvalue.rs
@@ -496,10 +496,10 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             mir::Rvalue::NullaryOp(mir::NullOp::Box, content_ty) => {
-                let content_ty: Ty<'tcx> = self.monomorphize(&content_ty);
-                let (size, align) = bx.cx().layout_of(content_ty).size_and_align();
-                let llsize = bx.cx().const_usize(size.bytes());
-                let llalign = bx.cx().const_usize(align.abi());
+                let content_ty = self.monomorphize(&content_ty);
+                let content_layout = bx.cx().layout_of(content_ty);
+                let llsize = bx.cx().const_usize(content_layout.size.bytes());
+                let llalign = bx.cx().const_usize(content_layout.align.abi.bytes());
                 let box_layout = bx.cx().layout_of(bx.tcx().mk_box(content_ty));
                 let llty_ptr = bx.cx().backend_type(box_layout);
 
diff --git a/src/librustc_codegen_ssa/traits/builder.rs b/src/librustc_codegen_ssa/traits/builder.rs
index 3757c514d2c..0b3066f561c 100644
--- a/src/librustc_codegen_ssa/traits/builder.rs
+++ b/src/librustc_codegen_ssa/traits/builder.rs
@@ -15,10 +15,10 @@ use super::intrinsic::IntrinsicCallMethods;
 use super::type_::ArgTypeMethods;
 use super::HasCodegen;
 use common::{AtomicOrdering, AtomicRmwBinOp, IntPredicate, RealPredicate, SynchronizationScope};
-use std::ffi::CStr;
 use mir::operand::OperandRef;
 use mir::place::PlaceRef;
 use rustc::ty::layout::{Align, Size};
+use std::ffi::CStr;
 use MemFlags;
 
 use std::borrow::Cow;
diff --git a/src/librustc_codegen_ssa/traits/type_.rs b/src/librustc_codegen_ssa/traits/type_.rs
index 1aa1f45f517..15976ac516d 100644
--- a/src/librustc_codegen_ssa/traits/type_.rs
+++ b/src/librustc_codegen_ssa/traits/type_.rs
@@ -120,16 +120,16 @@ pub trait DerivedTypeMethods<'tcx>: BaseTypeMethods<'tcx> + MiscMethods<'tcx> {
         }
     }
 
-    fn type_pointee_for_abi_align(&self, align: Align) -> Self::Type {
+    fn type_pointee_for_align(&self, align: Align) -> Self::Type {
         // FIXME(eddyb) We could find a better approximation if ity.align < align.
-        let ity = layout::Integer::approximate_abi_align(self, align);
+        let ity = layout::Integer::approximate_align(self, align);
         self.type_from_integer(ity)
     }
 
     /// Return a LLVM type that has at most the required alignment,
     /// and exactly the required size, as a best-effort padding array.
     fn type_padding_filler(&self, size: Size, align: Align) -> Self::Type {
-        let unit = layout::Integer::approximate_abi_align(self, align);
+        let unit = layout::Integer::approximate_align(self, align);
         let size = size.bytes();
         let unit_size = unit.size().bytes();
         assert_eq!(size % unit_size, 0);