tree 2179380ee3eb38fb393719e6ce32b15e934c4a44
parent d8470b7c13e11c18cf14a7e3180f0b00e715e4f0
author David Mosberger-Tang <[EMAIL PROTECTED]> Fri, 22 Apr 2005 01:07:59 -0700
committer Tony Luck <[EMAIL PROTECTED]> Fri, 22 Apr 2005 01:07:59 -0700
[IA64] fix fls()
The ia64-version of fls() never worked as intended (the bitnumbering
was off by 1 and fls(0) was undefined). This patch fixes the problem
by using a popcnt-based fls(), which on McKinley-derived cores is
slightly faster than both ia64_fls() and generic_fls(). The resulting
code, however, is bigger (7-8 bundles instead of about 3 bundles).
Also switch ia64_popcnt() to __builtin_popcountl() for GCC v3.4 or
newer since the compiler can predicate that and schedule it better.
Thanks to Simon Derr and Matt Mackall for tracking down this bug.
Signed-off-by: David Mosberger-Tang <[EMAIL PROTECTED]>
Signed-off-by: Tony Luck <[EMAIL PROTECTED]>
asm-ia64/bitops.h | 21 +++++++++++++++++----
asm-ia64/gcc_intrin.h | 10 +++++++---
2 files changed, 24 insertions(+), 7 deletions(-)
Index: include/asm-ia64/bitops.h
===================================================================
--- c92b15c165366a6d5c616305cb4b68349882cb61/include/asm-ia64/bitops.h
(mode:100644 sha1:925d54cee475ed9976455fddb35f8768f6020ff0)
+++ 2179380ee3eb38fb393719e6ce32b15e934c4a44/include/asm-ia64/bitops.h
(mode:100644 sha1:7232528e2d0c13771f6f62af20de13455aedb30b)
@@ -314,8 +314,8 @@ __ffs (unsigned long x)
#ifdef __KERNEL__
/*
- * find_last_zero_bit - find the last zero bit in a 64 bit quantity
- * @x: The value to search
+ * Return bit number of last (most-significant) bit set. Undefined
+ * for x==0. Bits are numbered from 0..63 (e.g., ia64_fls(9) == 3).
*/
static inline unsigned long
ia64_fls (unsigned long x)
@@ -327,10 +327,23 @@ ia64_fls (unsigned long x)
return exp - 0xffff;
}
+/*
+ * Find the last (most significant) bit set. Returns 0 for x==0 and
+ * bits are numbered from 1..32 (e.g., fls(9) == 4).
+ */
static inline int
-fls (int x)
+fls (int t)
{
- return ia64_fls((unsigned int) x);
+ unsigned long x = t & 0xffffffffu;
+
+ if (!x)
+ return 0;
+ x |= x >> 1;
+ x |= x >> 2;
+ x |= x >> 4;
+ x |= x >> 8;
+ x |= x >> 16;
+ return ia64_popcnt(x);
}
/*
Index: include/asm-ia64/gcc_intrin.h
===================================================================
--- c92b15c165366a6d5c616305cb4b68349882cb61/include/asm-ia64/gcc_intrin.h
(mode:100644 sha1:7c357dfbae50dc400b63c39e0f6add7a214a28a7)
+++ 2179380ee3eb38fb393719e6ce32b15e934c4a44/include/asm-ia64/gcc_intrin.h
(mode:100644 sha1:4fb4e439b05c35eca06daf2762936939c3e1b333)
@@ -133,13 +133,17 @@ register unsigned long ia64_r13 asm ("r1
ia64_intri_res;
\
})
-#define ia64_popcnt(x) \
-({ \
+#if __GNUC__ >= 4 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+# define ia64_popcnt(x) __builtin_popcountl(x)
+#else
+# define ia64_popcnt(x) \
+ ({ \
__u64 ia64_intri_res; \
asm ("popcnt %0=%1" : "=r" (ia64_intri_res) : "r" (x)); \
\
ia64_intri_res; \
-})
+ })
+#endif
#define ia64_getf_exp(x) \
({ \
-
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