[PATCH v8 03/17] xen/bitops: implement fls{l}() in common logic

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Return type was left 'int' because of the following compilation error:

./include/xen/kernel.h:18:21: error: comparison of distinct pointer types lacks 
a cast [-Werror]
       18 |         (void) (&_x == &_y);            \
          |                     ^~
    common/page_alloc.c:1843:34: note: in expansion of macro 'min'
     1843 |         unsigned int inc_order = min(MAX_ORDER, flsl(e - s) - 1);

generic_fls{l} was used instead of __builtin_clz{l}(x) as if x is 0,
the result in undefined.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 The patch is almost independent from Andrew's patch series
 ( 
https://lore.kernel.org/xen-devel/20240313172716.2325427-1-andrew.cooper3@xxxxxxxxxx/T/#t)
 except test_fls() function which IMO can be merged as a separate patch after 
Andrew's patch
 will be fully ready.
---
Changes in V8:
 - do proper rebase: back definition of fls{l} to the current patch.
 - drop the changes which removed ffz() in PPC. it should be done not
   in this patch.
 - add a message after Signed-off.
---
Changes in V7:
 - Code style fixes
---
Changes in V6:
 - new patch for the patch series.
---
 xen/arch/arm/include/asm/arm32/bitops.h |  2 +-
 xen/arch/arm/include/asm/arm64/bitops.h |  6 ++----
 xen/arch/arm/include/asm/bitops.h       |  7 ++-----
 xen/arch/ppc/include/asm/bitops.h       |  3 ---
 xen/arch/x86/include/asm/bitops.h       |  6 ++++--
 xen/common/bitops.c                     | 22 ++++++++++++++++++++++
 xen/include/xen/bitops.h                | 24 ++++++++++++++++++++++++
 7 files changed, 55 insertions(+), 15 deletions(-)

diff --git a/xen/arch/arm/include/asm/arm32/bitops.h 
b/xen/arch/arm/include/asm/arm32/bitops.h
index d0309d47c1..5552d4e945 100644
--- a/xen/arch/arm/include/asm/arm32/bitops.h
+++ b/xen/arch/arm/include/asm/arm32/bitops.h
@@ -1,7 +1,7 @@
 #ifndef _ARM_ARM32_BITOPS_H
 #define _ARM_ARM32_BITOPS_H
 
-#define flsl fls
+#define arch_flsl fls
 
 /*
  * Little endian assembly bitops.  nr = 0 -> byte 0 bit 0.
diff --git a/xen/arch/arm/include/asm/arm64/bitops.h 
b/xen/arch/arm/include/asm/arm64/bitops.h
index 0efde29068..5f5d97faa0 100644
--- a/xen/arch/arm/include/asm/arm64/bitops.h
+++ b/xen/arch/arm/include/asm/arm64/bitops.h
@@ -22,17 +22,15 @@ static /*__*/always_inline unsigned long __ffs(unsigned 
long word)
  */
 #define ffz(x)  __ffs(~(x))
 
-static inline int flsl(unsigned long x)
+static inline int arch_flsl(unsigned long x)
 {
         uint64_t ret;
 
-        if (__builtin_constant_p(x))
-               return generic_flsl(x);
-
         asm("clz\t%0, %1" : "=r" (ret) : "r" (x));
 
         return BITS_PER_LONG - ret;
 }
+#define arch_flsl arch_flsl
 
 /* Based on linux/include/asm-generic/bitops/find.h */
 
diff --git a/xen/arch/arm/include/asm/bitops.h 
b/xen/arch/arm/include/asm/bitops.h
index 8e16335e76..860d6d4689 100644
--- a/xen/arch/arm/include/asm/bitops.h
+++ b/xen/arch/arm/include/asm/bitops.h
@@ -78,17 +78,14 @@ bool clear_mask16_timeout(uint16_t mask, volatile void *p,
  * the clz instruction for much better code efficiency.
  */
 
-static inline int fls(unsigned int x)
+static inline int arch_fls(unsigned int x)
 {
         int ret;
 
-        if (__builtin_constant_p(x))
-               return generic_fls(x);
-
         asm("clz\t%"__OP32"0, %"__OP32"1" : "=r" (ret) : "r" (x));
         return 32 - ret;
 }
-
+#define arch_fls arch_fls
 
 #define arch_ffs(x) ({ unsigned int __t = (x); fls(ISOLATE_LSB(__t)); })
 #define arch_ffsl(x) ({ unsigned long __t = (x); flsl(ISOLATE_LSB(__t)); })
diff --git a/xen/arch/ppc/include/asm/bitops.h 
b/xen/arch/ppc/include/asm/bitops.h
index e2b6473c8c..ca308fd62b 100644
--- a/xen/arch/ppc/include/asm/bitops.h
+++ b/xen/arch/ppc/include/asm/bitops.h
@@ -119,9 +119,6 @@ static inline int test_and_set_bit(unsigned int nr, 
volatile void *addr)
         (volatile unsigned int *)addr + BITOP_WORD(nr)) != 0;
 }
 
-#define flsl(x) generic_flsl(x)
-#define fls(x) generic_fls(x)
-
 /* Based on linux/include/asm-generic/bitops/ffz.h */
 /*
  * ffz - find first zero in word.
diff --git a/xen/arch/x86/include/asm/bitops.h 
b/xen/arch/x86/include/asm/bitops.h
index 2b2d9219ef..5d5b9445c5 100644
--- a/xen/arch/x86/include/asm/bitops.h
+++ b/xen/arch/x86/include/asm/bitops.h
@@ -430,7 +430,7 @@ static always_inline unsigned int arch_ffsl(unsigned long x)
  *
  * This is defined the same way as ffs.
  */
-static inline int flsl(unsigned long x)
+static always_inline int arch_flsl(unsigned long x)
 {
     long r;
 
@@ -440,8 +440,9 @@ static inline int flsl(unsigned long x)
           "1:" : "=r" (r) : "rm" (x));
     return (int)r+1;
 }
+#define arch_flsl arch_flsl
 
-static inline int fls(unsigned int x)
+static always_inline int arch_fls(unsigned int x)
 {
     int r;
 
@@ -451,6 +452,7 @@ static inline int fls(unsigned int x)
           "1:" : "=r" (r) : "rm" (x));
     return r + 1;
 }
+#define arch_fls arch_fls
 
 /**
  * hweightN - returns the hamming weight of a N-bit word
diff --git a/xen/common/bitops.c b/xen/common/bitops.c
index a8c32f6767..95bc47176b 100644
--- a/xen/common/bitops.c
+++ b/xen/common/bitops.c
@@ -62,9 +62,31 @@ static void test_ffs(void)
     CHECK(ffs64, (uint64_t)0x8000000000000000, 64);
 }
 
+static void test_fls(void)
+{
+    /* unsigned int ffs(unsigned int) */
+    CHECK(fls, 1, 1);
+    CHECK(fls, 3, 2);
+    CHECK(fls, 3U << 30, 32);
+
+    /* unsigned int flsl(unsigned long) */
+    CHECK(flsl, 1, 1);
+    CHECK(flsl, 1UL << (BITS_PER_LONG - 1), BITS_PER_LONG);
+#if BITS_PER_LONG > 32
+    CHECK(flsl, 3UL << 32, 34);
+#endif
+
+    /* unsigned int fls64(uint64_t) */
+    CHECK(fls64, 1, 1);
+    CHECK(fls64, 0x00000000C0000000ULL, 32);
+    CHECK(fls64, 0x0000000180000000ULL, 33);
+    CHECK(fls64, 0xC000000000000000ULL, 64);
+}
+
 static int __init cf_check test_bitops(void)
 {
     test_ffs();
+    test_fls();
 
     return 0;
 }
diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index a41ec44064..a7edee4a95 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -196,6 +196,30 @@ static always_inline bool test_bit(int nr, const volatile 
void *addr)
     test_bit(nr, addr);                                 \
 })
 
+static always_inline __pure int fls(unsigned int x)
+{
+    if ( __builtin_constant_p(x) )
+        return generic_fls(x);
+
+#ifndef arch_fls
+#define arch_fls generic_fls
+#endif
+
+    return arch_fls(x);
+}
+
+static always_inline __pure int flsl(unsigned long x)
+{
+    if ( __builtin_constant_p(x) )
+        return generic_flsl(x);
+
+#ifndef arch_flsl
+#define arch_flsl generic_flsl
+#endif
+
+    return arch_flsl(x);
+}
+
 /*
  * Find First Set bit.  Bits are labelled from 1.
  */
-- 
2.44.0