xserver: Branch 'master'

[GitLab Mirror]

 dix/devices.c |   10 ----------
 os/osdep.h    |   23 ++++++++++++++++++++++-
 2 files changed, 22 insertions(+), 11 deletions(-)

New commits:
commit 45c485bfdf2e0d5049458ef9385a6347cec9ca32
Author: Alan Coopersmith <alan.coopersmith at oracle.com>
Date:   Sun Sep 8 14:54:46 2024 -0700

    dix: Use __builtin_popcountl if available to replace Ones()
    
    If the compiler knows of a better algorithm for counting the number of
    bits set in a word for the target CPU, let it use that, instead of the
    classic algorithm optimized for PDP-6.
    
    Based on xorg/lib/libxext at 490a25e6f8a4d2482af4364c700b68ad11a4d10b
    
    v2: make old version static inline, stop exporting after !1695
    
    Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
    Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1674>

diff --git a/dix/devices.c b/dix/devices.c
index 922e85ae0..750437ab2 100644
--- a/dix/devices.c
+++ b/dix/devices.c
@@ -2018,16 +2018,6 @@ NoteLedState(DeviceIntPtr keybd, int led, Bool on)
         ctrl->leds &= ~((Leds) 1 << (led - 1));
 }
 
-int
-Ones(unsigned long mask)
-{                               /* HACKMEM 169 */
-    unsigned long y;
-
-    y = (mask >> 1) & 033333333333;
-    y = mask - y - ((y >> 1) & 033333333333);
-    return (((y + (y >> 3)) & 030707070707) % 077);
-}
-
 static int
 DoChangeKeyboardControl(ClientPtr client, DeviceIntPtr keybd, XID *vlist,
                         BITS32 vmask)
diff --git a/os/osdep.h b/os/osdep.h
index 90df49d35..8d2f0678e 100644
--- a/os/osdep.h
+++ b/os/osdep.h
@@ -63,6 +63,10 @@ SOFTWARE.
 #include <X11/Xmd.h>
 #include <X11/Xdefs.h>
 
+#ifndef __has_builtin
+# define __has_builtin(x) 0     /* Compatibility with older compilers */
+#endif
+
 /* If EAGAIN and EWOULDBLOCK are distinct errno values, then we check errno
  * for both EAGAIN and EWOULDBLOCK, because some supposedly POSIX
  * systems are broken and return EWOULDBLOCK when they should return EAGAIN
@@ -215,6 +219,23 @@ extern Bool CoreDump;
 extern Bool NoListenAll;
 extern Bool AllowByteSwappedClients;
 
-int Ones(unsigned long mask);
+#if __has_builtin(__builtin_popcountl)
+# define Ones __builtin_popcountl
+#else
+/*
+ * Count the number of bits set to 1 in a 32-bit word.
+ * Algorithm from MIT AI Lab Memo 239: "HAKMEM", ITEM 169.
+ * https://dspace.mit.edu/handle/1721.1/6086
+ */
+static inline int
+Ones(unsigned long mask)
+{
+    unsigned long y;
+
+    y = (mask >> 1) & 033333333333;
+    y = mask - y - ((y >> 1) & 033333333333);
+    return (((y + (y >> 3)) & 030707070707) % 077);
+}
+#endif
 
 #endif                          /* _OSDEP_H_ */