Update detection of tool-chain support for MPX insns

to better work for older assemblers.
Pertains to BZ #339542.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14805

diff --git a/configure.ac b/configure.ac
index 11986775dcd3dc50c39b9b654415774e2cc4afbc..1298b293c21df835ef0659c9b379698718bb2bc8 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -2260,7 +2260,10 @@ AM_CONDITIONAL(BUILD_FMA_TESTS, test x$ac_have_as_fma = xyes)
 AC_MSG_CHECKING([if amd64 assembler knows the MPX instructions])
 
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[
-  asm ("bndmov %bnd0,(%rsp)")
+  do {
+    asm ("bndmov %bnd0,(%rsp)");
+    asm ("bndldx 3(%rbx,%rdx), %bnd2");
+  } while (0)
 ]])], [
 ac_have_as_mpx=yes
 AC_MSG_RESULT([yes])