Added configure test that checks whether the assembler supports the SSE4a instruction lzcnt.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@11357 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/configure.in b/configure.in
index a47fede..424a404 100644
--- a/configure.in
+++ b/configure.in
@@ -1410,6 +1410,24 @@
AM_CONDITIONAL(BUILD_SSSE3_TESTS, test x$ac_have_as_ssse3 = xyes)
+AC_MSG_CHECKING([if x86/amd64 assembler supports 'lzcnt'])
+
+AC_TRY_COMPILE([], [
+ do {
+ __asm__ __volatile__("lzcnt %rax,%rax");
+ } while (0)
+],
+[
+ ac_have_as_lzcnt=yes
+ AC_MSG_RESULT([yes])
+], [
+ ac_have_as_lzcnt=no
+ AC_MSG_RESULT([no])
+])
+
+AM_CONDITIONAL([BUILD_LZCNT_TESTS], [test x$ac_have_as_lzcnt = xyes])
+
+
# Check for TLS support in the compiler and linker
if test "x${cross_compiling}" = "xno"; then
# Native compilation: check whether running a program using TLS succeeds.