Check for _BitScanForward64 before using it

1 files changed, 7 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 29c0a3b7..8e3ee808 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -487,6 +487,13 @@ IF(HAVE_INTRIN_H)
             __cpuid(regs, 0);
             return regs[0];
         }" HAVE_CPUID_INTRINSIC)
+    CHECK_C_SOURCE_COMPILES("#include <intrin.h>
+        int main()
+        {
+            unsigned long idx = 0;
+            _BitScanForward64(&idx, 1);
+            return idx;
+        }" HAVE_BITSCANFORWARD64_INTRINSIC)
 ENDIF()
 
 CHECK_SYMBOL_EXISTS(sysconf          unistd.h HAVE_SYSCONF)