[PATCH 2/5] hurd: Microoptimize sigreturn

[Sergey Bugaev]

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---

I'll understand if this patch will be rejected, since this is not a hot path.
But I just couldn't help myself when I saw what this was being compiled to!
Much cleaner now.

If you don't like THREAD_GETMEM (THREAD_SELF, _hurd_sigstate), we could have
_hurd_self_sigstate_fast () or something.

 sysdeps/mach/hurd/i386/sigreturn.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/sysdeps/mach/hurd/i386/sigreturn.c 
b/sysdeps/mach/hurd/i386/sigreturn.c
index a0fc8891..6ad8a998 100644
--- a/sysdeps/mach/hurd/i386/sigreturn.c
+++ b/sysdeps/mach/hurd/i386/sigreturn.c
@@ -29,7 +29,12 @@ static void
 __sigreturn2 (int *usp, struct sigcontext *scp)
 {
   mach_port_t reply_port;
-  struct hurd_sigstate *ss = _hurd_self_sigstate ();
+  struct hurd_sigstate *ss;
+
+  /* We know the sigstate must be initialized, but the compiler does not.
+     Help it out a little bit by eliding the check that _hurd_self_sigstate
+     makes otherwise.  */
+  ss = THREAD_GETMEM (THREAD_SELF, _hurd_sigstate);
   _hurd_sigstate_unlock (ss);
 
   /* Destroy the MiG reply port used by the signal handler, and restore the
@@ -44,7 +49,7 @@ __sigreturn2 (int *usp, struct sigcontext *scp)
      do.  */
   reply_port = THREAD_GETMEM (THREAD_SELF, reply_port);
   THREAD_SETMEM (THREAD_SELF, reply_port, MACH_PORT_DEAD);
-  if (MACH_PORT_VALID (reply_port))
+  if (__glibc_likely (MACH_PORT_VALID (reply_port)))
     (void) __mach_port_mod_refs (__mach_task_self (), reply_port,
                                  MACH_PORT_RIGHT_RECEIVE, -1);
   THREAD_SETMEM (THREAD_SELF, reply_port, scp->sc_reply_port);
@@ -69,6 +74,7 @@ __sigreturn2 (int *usp, struct sigcontext *scp)
   /* Firewall.  */
   A (hlt);
 #undef A
+  __builtin_unreachable ();
 }
 
 int
@@ -77,13 +83,14 @@ __sigreturn (struct sigcontext *scp)
   struct hurd_sigstate *ss;
   struct hurd_userlink *link = (void *) &scp[1];
 
-  if (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK))
+  if (__glibc_unlikely (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK)))
     {
       errno = EINVAL;
       return -1;
     }
 
-  ss = _hurd_self_sigstate ();
+  /* Same as above, microoptimize _hurd_self_sigstate.  */
+  ss = THREAD_GETMEM (THREAD_SELF, _hurd_sigstate);
   _hurd_sigstate_lock (ss);
 
   /* Remove the link on the `active resources' chain added by
-- 
2.39.2