[PATCH v2 08/13] xen/bitops: Implement ffsl() in common logic

[Andrew Cooper <andrew.cooper3@citrix.com>]

Just like ffs() in the previous changes.  Express the upper bound of the
testing in terms of BITS_PER_LONG as it varies between architectures.

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>

v2:
 * Swap to #if BITS_PER_LONG > 32 to avoid a compile error on arm32
 * Changes to mirror ffs() v2.
---
 xen/arch/arm/include/asm/bitops.h |  2 +-
 xen/arch/ppc/include/asm/bitops.h |  2 +-
 xen/arch/x86/include/asm/bitops.h | 35 ++++++++++++++++---------------
 xen/common/bitops.c               | 13 ++++++++++++
 xen/include/xen/bitops.h          | 12 +++++++++++
 5 files changed, 45 insertions(+), 19 deletions(-)

diff --git a/xen/arch/arm/include/asm/bitops.h b/xen/arch/arm/include/asm/bitops.h
index a88ec2612e16..ba39802c9de3 100644
--- a/xen/arch/arm/include/asm/bitops.h
+++ b/xen/arch/arm/include/asm/bitops.h
@@ -158,7 +158,7 @@ static inline int fls(unsigned int x)
 
 
 #define arch_ffs(x)  ((x) ? 1 + __builtin_ctz(x) : 0)
-#define ffsl(x) ({ unsigned long __t = (x); flsl(ISOLATE_LSB(__t)); })
+#define arch_ffsl(x) ((x) ? 1 + __builtin_ctzl(x) : 0)
 
 /**
  * find_first_set_bit - find the first set bit in @word
diff --git a/xen/arch/ppc/include/asm/bitops.h b/xen/arch/ppc/include/asm/bitops.h
index 5c36a6cc0ce3..ce0f6436f727 100644
--- a/xen/arch/ppc/include/asm/bitops.h
+++ b/xen/arch/ppc/include/asm/bitops.h
@@ -174,7 +174,7 @@ static inline int __test_and_clear_bit(int nr, volatile void *addr)
 #define flsl(x) generic_flsl(x)
 #define fls(x) generic_flsl(x)
 #define arch_ffs(x)  ((x) ? 1 + __builtin_ctz(x) : 0)
-#define ffsl(x) ({ unsigned long t_ = (x); flsl(t_ & -t_); })
+#define arch_ffsl(x) ((x) ? 1 + __builtin_ctzl(x) : 0)
 
 /**
  * hweightN - returns the hamming weight of a N-bit word
diff --git a/xen/arch/x86/include/asm/bitops.h b/xen/arch/x86/include/asm/bitops.h
index 1d7aea6065ef..51d3c0f40473 100644
--- a/xen/arch/x86/include/asm/bitops.h
+++ b/xen/arch/x86/include/asm/bitops.h
@@ -413,23 +413,6 @@ static inline unsigned int find_first_set_bit(unsigned long word)
     return (unsigned int)word;
 }
 
-/**
- * ffs - find first bit set
- * @x: the word to search
- *
- * This is defined the same way as the libc and compiler builtin ffs routines.
- */
-static inline int ffsl(unsigned long x)
-{
-    long r;
-
-    asm ( "bsf %1,%0\n\t"
-          "jnz 1f\n\t"
-          "mov $-1,%0\n"
-          "1:" : "=r" (r) : "rm" (x));
-    return (int)r+1;
-}
-
 static always_inline unsigned int arch_ffs(unsigned int x)
 {
     unsigned int r;
@@ -458,6 +441,24 @@ static always_inline unsigned int arch_ffs(unsigned int x)
 }
 #define arch_ffs arch_ffs
 
+static always_inline unsigned int arch_ffsl(unsigned long x)
+{
+    unsigned int r;
+
+    /* See arch_ffs() for safety discussions. */
+    if ( __builtin_constant_p(x > 0) && x > 0 )
+        asm ( "bsf %[val], %q[res]"
+              : [res] "=r" (r)
+              : [val] "rm" (x) );
+    else
+        asm ( "bsf %[val], %q[res]"
+              : [res] "=r" (r)
+              : [val] "rm" (x), "[res]" (-1) );
+
+    return r + 1;
+}
+#define arch_ffsl arch_ffsl
+
 /**
  * fls - find last bit set
  * @x: the word to search
diff --git a/xen/common/bitops.c b/xen/common/bitops.c
index 8c161b8ea7fa..b3813f818198 100644
--- a/xen/common/bitops.c
+++ b/xen/common/bitops.c
@@ -11,6 +11,19 @@ static void __init test_ffs(void)
     CHECK(ffs, 7, 1);
     CHECK(ffs, 6, 2);
     CHECK(ffs, 0x80000000U, 32);
+
+    /* unsigned int ffsl(unsigned long) */
+    CHECK(ffsl, 0, 0);
+    CHECK(ffsl, 1, 1);
+    CHECK(ffsl, 3, 1);
+    CHECK(ffsl, 7, 1);
+    CHECK(ffsl, 6, 2);
+
+    CHECK(ffsl, 1UL << (BITS_PER_LONG - 1), BITS_PER_LONG);
+#if BITS_PER_LONG > 32
+    CHECK(ffsl, 1UL << 32, 33);
+    CHECK(ffsl, 1UL << 63, 64);
+#endif
 }
 
 static void __init __constructor test_bitops(void)
diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index f7e90a2893a5..88cf27a88bcf 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -48,6 +48,18 @@ static always_inline __pure unsigned int ffs(unsigned int x)
 #endif
 }
 
+static always_inline __pure unsigned int ffsl(unsigned long x)
+{
+    if ( __builtin_constant_p(x) )
+        return __builtin_ffsl(x);
+
+#ifdef arch_ffs
+    return arch_ffsl(x);
+#else
+    return generic_ffsl(x);
+#endif
+}
+
 /* --------------------- Please tidy below here --------------------- */
 
 #ifndef find_next_bit
-- 
2.30.2