[libunwind] r311574 - ARM: explicitly specify the 8-byte alignment

[Saleem Abdulrasool via cfe-commits]

Author: compnerd
Date: Wed Aug 23 09:50:27 2017
New Revision: 311574

URL: http://llvm.org/viewvc/llvm-project?rev=311574&view=rev
Log:
ARM: explicitly specify the 8-byte alignment

It seems that GCC interprets `__attribute__((__aligned__))` as 8-byte
alignment on ARM, but clang does not.  Explicitly specify the
double-word alignment value to ensure that the structure is properly
aligned.

Modified:
    libunwind/trunk/include/unwind.h
    libunwind/trunk/test/alignment.pass.cpp

Modified: libunwind/trunk/include/unwind.h
URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/include/unwind.h?rev=311574&r1=311573&r2=311574&view=diff
==============================================================================
--- libunwind/trunk/include/unwind.h (original)
+++ libunwind/trunk/include/unwind.h Wed Aug 23 09:50:27 2017
@@ -100,7 +100,7 @@ struct _Unwind_Control_Block {
   } pr_cache;
 
   long long int :0; /* Enforce the 8-byte alignment */
-} __attribute__((__aligned__));
+} __attribute__((__aligned__(8)));
 
 typedef _Unwind_Reason_Code (*_Unwind_Stop_Fn)
       (_Unwind_State state,

Modified: libunwind/trunk/test/alignment.pass.cpp
URL: http://llvm.org/viewvc/llvm-project/libunwind/trunk/test/alignment.pass.cpp?rev=311574&r1=311573&r2=311574&view=diff
==============================================================================
--- libunwind/trunk/test/alignment.pass.cpp (original)
+++ libunwind/trunk/test/alignment.pass.cpp Wed Aug 23 09:50:27 2017
@@ -13,8 +13,16 @@
 
 #include <unwind.h>
 
-struct MaxAligned {} __attribute__((aligned));
-static_assert(alignof(_Unwind_Exception) == alignof(MaxAligned), "");
+// EHABI  : 8-byte aligned
+// itanium: largest supported alignment for the system
+#if defined(_LIBUNWIND_ARM_EHABI)
+static_assert(alignof(_Unwind_Control_Block) == 8,
+              "_Unwind_Control_Block must be double-word aligned");
+#else
+struct MaxAligned {} __attribute__((__aligned__));
+static_assert(alignof(_Unwind_Exception) == alignof(MaxAligned),
+              "_Unwind_Exception must be maximally aligned");
+#endif
 
 int main()
 {