Force LLVM to generate byte-aligned packed unions

Sometimes the frontend and LLVM would disagree on the ABI alignment of a
packed union. Solve the problem by telling LLVM we're gonna manage the
struct layout by ourselves.

Closes #3184

1 files changed, 12 insertions, 0 deletions

diff --git a/test/stage1/behavior/union.zig b/test/stage1/behavior/union.zig
index 7c5c653275..21308b0ea2 100644
--- a/test/stage1/behavior/union.zig
+++ b/test/stage1/behavior/union.zig
@@ -482,3 +482,15 @@ test "comparison between union and enum literal" {
     testComparison();
     comptime testComparison();
 }
+
+test "packed union generates correctly aligned LLVM type" {
+    const U = packed union {
+        f1: fn () void,
+        f2: u32,
+    };
+    var foo = [_]U{
+        U{ .f1 = doTest },
+        U{ .f2 = 0 },
+    };
+    foo[0].f1();
+}