| Submitter | Paolo Bonzini |
|---|---|
| Date | Sept. 26, 2012, 3:56 p.m. |
| Message ID | <1348675011-8794-35-git-send-email-pbonzini@redhat.com> |
| Download | mbox | patch |
| Permalink | /patch/187124/ |
| State | New |
| Headers | show |
Comments
On 09/26/2012 09:56 AM, Paolo Bonzini wrote: > 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. > Why glibc chose <string.h> for ffsl even though it uses <strings.h> for ffs (per POSIX) is beyond me. At any rate, this report spurred me to finally file an enhancement request against POSIX: http://www.austingroupbugs.net/view.php?id=617 Someday in the future, we might just get ffsl standardized. :)
Patch
diff --git a/host-utils.h b/host-utils.h index 821db93..2724be0 100644 --- a/host-utils.h +++ b/host-utils.h @@ -24,6 +24,7 @@ */ #include "compiler.h" /* QEMU_GNUC_PREREQ */ +#include <string.h> /* ffsl */ #if defined(__x86_64__) #define __HAVE_FAST_MULU64__ @@ -234,3 +235,28 @@ static inline int ctpop64(uint64_t val) return 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 +}
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. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- host-utils.h | 26 ++++++++++++++++++++++++++ 1 file modificato, 26 inserzioni(+)