[Midnightbsd-cvs] src [8614] trunk/contrib/gcc4/unwind-dw2.c: add ugly hack to ligcc unwind code to make it behave properly at runtime on amd64 when compiled by clang

[laffer1 at midnightbsd.org]

Revision: 8614
          http://svnweb.midnightbsd.org/src/?rev=8614
Author:   laffer1
Date:     2016-09-25 13:39:47 -0400 (Sun, 25 Sep 2016)
Log Message:
-----------
add ugly hack to ligcc unwind code to make it behave properly at runtime on amd64 when compiled by clang

Modified Paths:
--------------
    trunk/contrib/gcc4/unwind-dw2.c

Modified: trunk/contrib/gcc4/unwind-dw2.c
===================================================================
--- trunk/contrib/gcc4/unwind-dw2.c	2016-09-25 17:38:53 UTC (rev 8613)
+++ trunk/contrib/gcc4/unwind-dw2.c	2016-09-25 17:39:47 UTC (rev 8614)
@@ -1438,6 +1438,17 @@
   context->ra = __builtin_extract_return_addr (outer_ra);
 }
 
+#if defined(__clang__) && defined(__amd64__)
+/* Some versions of clang don't save and restore all callee registers, if a
+   __builtin_eh_return() intrinsic is used in a function.  This is particularly
+   bad on amd64.  For now, use the following ugly hack to force it to assume
+   those registers are clobbered, when invoking __builtin_eh_return(), so it
+   will emit code to save and restore them.  */
+#define CLOBBER_REGS_HACK \
+  __asm __volatile(" " : : : "r15", "r14", "r13", "r12", "rbx", "rdx", "rax");
+#else
+#define CLOBBER_REGS_HACK
+#endif /* __clang__ */
 
 /* Install TARGET into CURRENT so that we can return to it.  This is a
    macro because __builtin_eh_return must be invoked in the context of
@@ -1448,6 +1459,7 @@
     {									 \
       long offset = uw_install_context_1 ((CURRENT), (TARGET));		 \
       void *handler = __builtin_frob_return_addr ((TARGET)->ra);	 \
+      CLOBBER_REGS_HACK							 \
       __builtin_eh_return (offset, handler);				 \
     }									 \
   while (0)