Patchwork [v3,01/12] host-utils: add ffsl

login
register
mail settings
Submitter Paolo Bonzini
Date Jan. 21, 2013, 4:09 p.m.
Message ID <1358784590-16288-2-git-send-email-pbonzini@redhat.com>
Download mbox | patch
Permalink /patch/214206/
State New
Headers show

Comments

Paolo Bonzini - Jan. 21, 2013, 4:09 p.m.
We can provide fast versions based on the other functions defined
by host-utils.h.  Some care is required on glibc, which provides
ffsl already.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/host-utils.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

Patch

diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h
index 81c9a75..2a32be4 100644
--- a/include/qemu/host-utils.h
+++ b/include/qemu/host-utils.h
@@ -26,6 +26,7 @@ 
 #define HOST_UTILS_H 1
 
 #include "qemu/compiler.h"   /* QEMU_GNUC_PREREQ */
+#include <string.h>     /* ffsl */
 
 #if defined(__x86_64__)
 #define __HAVE_FAST_MULU64__
@@ -237,4 +238,29 @@  static inline int ctpop64(uint64_t val)
 #endif
 }
 
+/* glibc does not provide an inline version of ffsl, so always define
+ * ours.  We need to give it a different name, however.
+ */
+#ifdef __GLIBC__
+#define ffsl qemu_ffsl
+#endif
+static inline int ffsl(long val)
+{
+    if (!val) {
+        return 0;
+    }
+
+#if QEMU_GNUC_PREREQ(3, 4)
+    return __builtin_ctzl(val) + 1;
+#else
+    if (sizeof(long) == 4) {
+        return ctz32(val) + 1;
+    } else if (sizeof(long) == 8) {
+        return ctz64(val) + 1;
+    } else {
+        abort();
+    }
+#endif
+}
+
 #endif