From c8be312933c375a76a021a947330f1024dc83b9a Mon Sep 17 00:00:00 2001
From: David Renshaw <david@sandstorm.io>
Date: Tue, 6 Jun 2017 09:49:34 -0400
Subject: [PATCH] fix issue 184 by marking the destination as a packed struct

---
 src/terminator/intrinsic.rs      | 11 ++++++++++-
 tests/run-pass/issue-miri-184.rs |  4 ++++
 2 files changed, 14 insertions(+), 1 deletion(-)
 create mode 100644 tests/run-pass/issue-miri-184.rs

diff --git a/src/terminator/intrinsic.rs b/src/terminator/intrinsic.rs
index 31886e9cc6d9..193b7c3cde17 100644
--- a/src/terminator/intrinsic.rs
+++ b/src/terminator/intrinsic.rs
@@ -383,8 +383,17 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
             }
 
             "transmute" => {
+                let src_ty = substs.type_at(0);
                 let dest_ty = substs.type_at(1);
-                self.write_value(arg_vals[0], dest, dest_ty)?;
+                let (_, src_align) = self.size_and_align_of_dst(src_ty, arg_vals[0])?;
+                let (size, dest_align) = self.size_and_align_of_dst(dest_ty, arg_vals[0])?;
+                if dest_align < src_align {
+                    let ptr = self.force_allocation(dest)?.to_ptr();
+                    self.memory.mark_packed(ptr, size);
+                    self.write_value_to_ptr(arg_vals[0], ptr, dest_ty)?;
+                } else {
+                    self.write_value(arg_vals[0], dest, dest_ty)?;
+                }
             }
 
             "uninit" => {
diff --git a/tests/run-pass/issue-miri-184.rs b/tests/run-pass/issue-miri-184.rs
new file mode 100644
index 000000000000..24775fe8a2d9
--- /dev/null
+++ b/tests/run-pass/issue-miri-184.rs
@@ -0,0 +1,4 @@
+pub fn main() {
+    let bytes: [u8; 8] = unsafe { ::std::mem::transmute(0u64) };
+    let _: &[u8] = &bytes;
+}