Auto merge of #39999 - bitshifter:struct_align, r=eddyb

Implementation of repr struct alignment RFC 1358.

The main changes around rustc::ty::Layout::struct:
* Added abi_align field which stores abi alignment before repr align is applied
* align field contains transitive repr alignment
* Added padding vec which stores padding required after fields

The main user of this information is rustc_trans::adt::struct_llfields
which determines the LLVM fields to be used by LLVM, including padding
fields.

A possible future optimisation would be to put the padding Vec in an Option, since it will be unused unless you are using repr align.

5 files changed, 73 insertions, 3 deletions

diff --git a/src/test/compile-fail/attr-usage-repr.rs b/src/test/compile-fail/attr-usage-repr.rs
index b07d3e2f906..c0bfd3690c8 100644
--- a/src/test/compile-fail/attr-usage-repr.rs
+++ b/src/test/compile-fail/attr-usage-repr.rs
@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![allow(dead_code)]
+#![feature(attr_literals)]
 #![feature(repr_simd)]
 
 #[repr(C)] //~ ERROR: attribute should be applied to struct, enum or union
@@ -29,6 +30,9 @@ struct SInt(f64, f64);
 #[repr(C)]
 enum EExtern { A, B }
 
+#[repr(align(8))] //~ ERROR: attribute should be applied to struct
+enum EAlign { A, B }
+
 #[repr(packed)] //~ ERROR: attribute should be applied to struct
 enum EPacked { A, B }
 
diff --git a/src/test/compile-fail/conflicting-repr-hints.rs b/src/test/compile-fail/conflicting-repr-hints.rs
index 9e0c0d845ca..01fa3ffbaa6 100644
--- a/src/test/compile-fail/conflicting-repr-hints.rs
+++ b/src/test/compile-fail/conflicting-repr-hints.rs
@@ -8,8 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(rustc_attrs)]
 #![allow(dead_code)]
+#![feature(attr_literals)]
+#![feature(repr_align)]
 
 #[repr(C)]
 enum A { A }
@@ -26,5 +27,7 @@ enum D { D }
 #[repr(C, packed)]
 struct E(i32);
 
-#[rustc_error]
-fn main() {} //~ ERROR compilation successful
+#[repr(packed, align(8))] //~ ERROR conflicting packed and align representation hints
+struct F(i32);
+
+fn main() {}
diff --git a/src/test/compile-fail/feature-gate-repr_align.rs b/src/test/compile-fail/feature-gate-repr_align.rs
new file mode 100644
index 00000000000..8e986e197f2
--- /dev/null
+++ b/src/test/compile-fail/feature-gate-repr_align.rs
@@ -0,0 +1,15 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+#![feature(attr_literals)]
+
+#[repr(align(64))]
+struct Foo(u64, u64); //~ error: the struct `#[repr(align(u16))]` attribute is experimental
+
+fn main() {}
diff --git a/src/test/compile-fail/repr-align.rs b/src/test/compile-fail/repr-align.rs
new file mode 100644
index 00000000000..eb0b27fe9c0
--- /dev/null
+++ b/src/test/compile-fail/repr-align.rs
@@ -0,0 +1,23 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+#![allow(dead_code)]
+#![feature(attr_literals)]
+#![feature(repr_align)]
+
+#[repr(align(16.0))] //~ ERROR: invalid `repr(align)` attribute: not an unsuffixed integer
+struct A(i32);
+
+#[repr(align(15))] //~ ERROR: invalid `repr(align)` attribute: not a power of two
+struct B(i32);
+
+#[repr(align(65536))] //~ ERROR: invalid `repr(align)` attribute: larger than 32768
+struct C(i32);
+
+fn main() {}
diff --git a/src/test/compile-fail/repr-packed-contains-align.rs b/src/test/compile-fail/repr-packed-contains-align.rs
new file mode 100644
index 00000000000..c584dcf3e59
--- /dev/null
+++ b/src/test/compile-fail/repr-packed-contains-align.rs
@@ -0,0 +1,25 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+#![feature(attr_literals)]
+#![feature(repr_align)]
+#![allow(dead_code)]
+
+#[repr(align(16))]
+struct A(i32);
+
+struct B(A);
+
+#[repr(packed)]
+struct C(A); //~ ERROR: packed struct cannot transitively contain a `[repr(align)]` struct
+
+#[repr(packed)]
+struct D(B); //~ ERROR: packed struct cannot transitively contain a `[repr(align)]` struct
+
+fn main() {}