Set proper alignment on constants

For enum variants, the default alignment for a specific variant might be
lower than the alignment of the enum type itself. In such cases we, for
example, generate memcpy calls with an alignment that's higher than the
alignment of the constant we copy from.

To avoid that, we need to explicitly set the required alignment on
constants.

Fixes #28912.

1 files changed, 66 insertions, 0 deletions

diff --git a/src/test/codegen/consts.rs b/src/test/codegen/consts.rs
new file mode 100644
index 00000000000..6b4e626df92
--- /dev/null
+++ b/src/test/codegen/consts.rs
@@ -0,0 +1,66 @@
+// Copyright 2015 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.
+
+// compile-flags: -C no-prepopulate-passes
+
+#![crate_type = "lib"]
+
+// Below, these constants are defined as enum variants that by itself would
+// have a lower alignment than the enum type. Ensure that we mark them
+// correctly with the higher alignment of the enum.
+
+// CHECK: @STATIC = {{.*}}, align 4
+
+// This checks the constants from inline_enum_const
+// CHECK: @const{{[0-9]+}} = {{.*}}, align 2
+
+// This checks the constants from {low,high}_align_const, they share the same
+// constant, but the alignment differs, so the higher one should be used
+// CHECK: @const{{[0-9]+}} = {{.*}}, align 4
+
+#[derive(Copy, Clone)]
+
+// repr(i16) is required for the {low,high}_align_const test
+#[repr(i16)]
+pub enum E<A, B> {
+    A(A),
+    B(B),
+}
+
+#[no_mangle]
+pub static STATIC: E<i16, i32> = E::A(0);
+
+// CHECK-LABEL: @static_enum_const
+#[no_mangle]
+pub fn static_enum_const() -> E<i16, i32> {
+   STATIC
+}
+
+// CHECK-LABEL: @inline_enum_const
+#[no_mangle]
+pub fn inline_enum_const() -> E<i8, i16> {
+    E::A(0)
+}
+
+// CHECK-LABEL: @low_align_const
+#[no_mangle]
+pub fn low_align_const() -> E<i16, [i16; 3]> {
+// Check that low_align_const and high_align_const use the same constant
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{[0-9]+}}, i8* {{.*}} [[LOW_HIGH:@const[0-9]+]]
+    E::A(0)
+}
+
+// CHECK-LABEL: @high_align_const
+#[no_mangle]
+pub fn high_align_const() -> E<i16, i32> {
+// Check that low_align_const and high_align_const use the same constant
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{[0-9]}}, i8* {{.*}} [[LOW_HIGH]]
+    E::A(0)
+}