1 files changed, 10 insertions, 0 deletions
diff --git a/target-i386/int_helper.c b/target-i386/int_helper.c
index 9d0d21e786..cf5bbb0481 100644
--- a/target-i386/int_helper.c
+++ b/target-i386/int_helper.c
@@ -470,3 +470,13 @@ target_ulong helper_pext(target_ulong src, target_ulong mask)
 #include "shift_helper_template.h"
 #undef SHIFT
 #endif
+
+/* Test that BIT is enabled in CR4.  If not, raise an illegal opcode
+   exception.  This reduces the requirements for rare CR4 bits being
+   mapped into HFLAGS.  */
+void helper_cr4_testbit(CPUX86State *env, uint32_t bit)
+{
+    if (unlikely((env->cr[4] & bit) == 0)) {
+        raise_exception_ra(env, EXCP06_ILLOP, GETPC());
+    }
+}