From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Sat, 09 Apr 2005 00:21:06 +0000 Subject: Re: [mpm@selenic.com: Re: buggy ia64_fls() ? (was Re: /dev/random Message-Id: <16983.8178.342410.690955@napali.hpl.hp.com> List-Id: References: <20050408103324.6c5231df.akpm@osdl.org> In-Reply-To: <20050408103324.6c5231df.akpm@osdl.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Here is a first cut for the patch. It compiles with gcc 3.3 and 3.4 and boots on Ski. Assuming nobody finds any issues, I'll make a final patch tonight. Thanks, --david === include/asm-ia64/bitops.h 1.19 vs edited ==--- 1.19/include/asm-ia64/bitops.h 2005-03-13 15:30:06 -08:00 +++ edited/include/asm-ia64/bitops.h 2005-04-08 17:17:09 -07:00 @@ -314,8 +314,8 @@ #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 @@ 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); } /* === include/asm-ia64/gcc_intrin.h 1.7 vs edited ==--- 1.7/include/asm-ia64/gcc_intrin.h 2004-10-05 11:27:40 -07:00 +++ edited/include/asm-ia64/gcc_intrin.h 2005-04-08 17:16:54 -07:00 @@ -133,13 +133,17 @@ 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) \ ({ \