target-i386: Optimize setting dr[0-3]

If the debug register is not enabled, we need
do nothing besides update the register.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

diff --git a/target-i386/bpt_helper.c b/target-i386/bpt_helper.c
index ca58ab78c7d55fceffc9b5a9bb19d47939171cb9..7ff41a6c975b5f90206354fbeabd28d29ecbd6bd 100644 (file)
--- a/target-i386/bpt_helper.c
+++ b/target-i386/bpt_helper.c
@@ -228,9 +228,14 @@ void helper_movl_drN_T0(CPUX86State *env, int reg, target_ulong t0)
 {
 #ifndef CONFIG_USER_ONLY
     if (reg < 4) {
-        hw_breakpoint_remove(env, reg);
-        env->dr[reg] = t0;
-        hw_breakpoint_insert(env, reg);
+        if (hw_breakpoint_enabled(env->dr[7], reg)
+            && hw_breakpoint_type(env->dr[7], reg) != DR7_TYPE_IO_RW) {
+            hw_breakpoint_remove(env, reg);
+            env->dr[reg] = t0;
+            hw_breakpoint_insert(env, reg);
+        } else {
+            env->dr[reg] = t0;
+        }
     } else if (reg == 7) {
         cpu_x86_update_dr7(env, t0);
     } else {