diff mbox series

[5/7] xen/bitops: Implement ffs64() in common logic

Message ID 20240313172716.2325427-6-andrew.cooper3@citrix.com (mailing list archive)
State New
Headers show
Series xen/bitops: Reduce the mess, starting with ffs() | expand

Commit Message

Andrew Cooper March 13, 2024, 5:27 p.m. UTC 
As per ffs()/ffsl() in previous patches.  Add tests for all interesting bit
positions at 32bit boundaries.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien@xen.org>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
CC: Bertrand Marquis <bertrand.marquis@arm.com>
CC: Michal Orzel <michal.orzel@amd.com>
CC: Oleksii Kurochko <oleksii.kurochko@gmail.com>
CC: Shawn Anastasio <sanastasio@raptorengineering.com>
CC: consulting@bugseng.com <consulting@bugseng.com>
CC: Simone Ballarin <simone.ballarin@bugseng.com>
CC: Federico Serafini <federico.serafini@bugseng.com>
CC: Nicola Vetrini <nicola.vetrini@bugseng.com>
---
 xen/common/bitops.c      | 12 ++++++++++++
 xen/include/xen/bitops.h | 16 ++++++++--------
 2 files changed, 20 insertions(+), 8 deletions(-)

Comments

Jan Beulich March 14, 2024, 3:56 p.m. UTC | #1 
On 13.03.2024 18:27, Andrew Cooper wrote:
> --- a/xen/common/bitops.c
> +++ b/xen/common/bitops.c
> @@ -47,6 +47,18 @@ static void test_ffs(void)
>      CHECK(ffsl, 1UL << (BITS_PER_LONG - 1), BITS_PER_LONG);
>      if ( BITS_PER_LONG > 32 )
>          CHECK(ffsl, 1UL << 32, 33);
> +
> +    /*
> +     * unsigned int ffs64(uint64_t)
> +     *
> +     * 32-bit builds of Xen have to split this into two adjacent operations,
> +     * so test all interesting bit positions.
> +     */
> +    CHECK(ffs64, 0, 0);
> +    CHECK(ffs64, 1, 1);
> +    CHECK(ffs64, (uint64_t)0x0000000080000000, 32);
> +    CHECK(ffs64, (uint64_t)0x0000000100000000, 33);
> +    CHECK(ffs64, (uint64_t)0x8000000000000000, 64);

I'm pretty sure Misra will want ULL suffixes on the last two and at least an UL
one on the middle of the lines. The casts aren't going to help (and could then
be dropped).

Jan
diff mbox series

Patch

diff --git a/xen/common/bitops.c b/xen/common/bitops.c
index eceffe5029d6..cd194fe672b7 100644
--- a/xen/common/bitops.c
+++ b/xen/common/bitops.c
@@ -47,6 +47,18 @@  static void test_ffs(void)
     CHECK(ffsl, 1UL << (BITS_PER_LONG - 1), BITS_PER_LONG);
     if ( BITS_PER_LONG > 32 )
         CHECK(ffsl, 1UL << 32, 33);
+
+    /*
+     * unsigned int ffs64(uint64_t)
+     *
+     * 32-bit builds of Xen have to split this into two adjacent operations,
+     * so test all interesting bit positions.
+     */
+    CHECK(ffs64, 0, 0);
+    CHECK(ffs64, 1, 1);
+    CHECK(ffs64, (uint64_t)0x0000000080000000, 32);
+    CHECK(ffs64, (uint64_t)0x0000000100000000, 33);
+    CHECK(ffs64, (uint64_t)0x8000000000000000, 64);
 }
 
 static int __init cf_check test_bitops(void)
diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index b85b35c40781..f14ad0d33aa3 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -96,6 +96,14 @@  static always_inline __pure unsigned int ffsl(unsigned long x)
     return arch_ffsl(x);
 }
 
+static always_inline __pure unsigned int ffs64(uint64_t x)
+{
+    if ( BITS_PER_LONG == 64 )
+        return ffsl(x);
+    else
+        return !x || (uint32_t)x ? ffs(x) : ffs(x >> 32) + 32;
+}
+
 /* --------------------- Please tidy below here --------------------- */
 
 #ifndef find_next_bit
@@ -148,15 +156,7 @@  extern unsigned long find_first_zero_bit(const unsigned long *addr,
 
 #if BITS_PER_LONG == 64
 # define fls64 flsl
-# define ffs64 ffsl
 #else
-# ifndef ffs64
-static inline int generic_ffs64(__u64 x)
-{
-    return !x || (__u32)x ? ffs(x) : ffs(x >> 32) + 32;
-}
-#  define ffs64 generic_ffs64
-# endif
 # ifndef fls64
 static inline int generic_fls64(__u64 x)
 {