clang+amd4: fix stack alignment for continuations.

* unwind.h (UW_FRAME_ALIGN): Define on __amd64__, if compiled
by __clang__. This is because MMX instructions are used for
manipulating the stack which require 16 byte alignment.
This was discovered as a bus error crash on OpenBSD in the
tests/012/cont.tl test case, acessing otherwise perfectly
valid memory. The faulting address was only 8 byte aligned,
not 16.

1 files changed, 1 insertions, 1 deletions

diff --git a/unwind.h b/unwind.h
index 35c2e017..a18ba351 100644
--- a/unwind.h
+++ b/unwind.h
@@ -302,7 +302,7 @@ struct uw_eval {
 
 #endif
 
-#if __aarch64__
+#if __aarch64__ || (__clang__ && __amd64__)
 #define UW_FRAME_ALIGN __attribute__ ((aligned (16)))
 #else
 #define UW_FRAME_ALIGN