cpumask: make "nr_cpumask_bits" unsigned

Bit searching functions accept "unsigned long" indices but "nr_cpumask_bits" is "int" which is signed, so inevitable sign extensions occur on x86_64. Those MOVSX are #1 MOVSX bloat by number of uses across whole kernel.

Change "nr_cpumask_bits" to unsigned, this number can't be negative after all. It allows to do implicit zero-extension on x86_64 without MOVSX.

Change signed comparisons into unsigned comparisons where necessary.

Other uses looks fine because it is either argument passed to a function or comparison is already unsigned.

Net win on allyesconfig type of kernel: ~2.8 KB (!)

add/remove: 0/0 grow/shrink: 8/725 up/down: 93/-2926 (-2833)
function old new delta
xen_exit_mmap 691 735 +44
qstat_read 426 440 +14
__cpufreq_cooling_register 1678 1687 +9
trace_rb_cpu_prepare 447 455 +8
vermagic 54 60 +6
nfp_driver_version 54 60 +6
rcu_torture_stats_print 1147 1151 +4
find_next_push_cpu 267 269 +2
xen_irq_resume 961 960 -1
...
init_vp_index 946 906 -40
od_set_powersave_bias 328 281 -47
power_cpu_exit 193 139 -54
arch_show_interrupts 3538 3484 -54
select_idle_sibling 1558 1471 -87
Total: Before=158358910, After=158356077, chg -0.00%

Same arguments apply to "nr_cpu_ids" but I haven't yet found enough courage to delve into this issue (and proper fix may require new type "cpu_t" which is whole separate story).

---

 arch/mips/kernel/perf_event_mipsxx.c |    2 +-
 arch/s390/kernel/perf_cpum_sf.c      |    2 +-
 include/linux/cpumask.h              |    4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

@@ -618,7 +618,7 @@ static int mipspmu_event_init(struct perf_event *event)
 		return -ENOENT;
 	}
 
-	if (event->cpu >= nr_cpumask_bits ||
+	if ((unsigned int)event->cpu >= nr_cpumask_bits ||
 	    (event->cpu >= 0 && !cpu_online(event->cpu)))
 		return -ENODEV;
 

@@ -823,7 +823,7 @@ static int cpumsf_pmu_event_init(struct perf_event *event)
 	}
 
 	/* Check online status of the CPU to which the event is pinned */
-	if (event->cpu >= nr_cpumask_bits ||
+	if ((unsigned int)event->cpu >= nr_cpumask_bits ||
 	    (event->cpu >= 0 && !cpu_online(event->cpu)))
 		return -ENODEV;
 

@@ -40,9 +40,9 @@ extern int nr_cpu_ids;
 #ifdef CONFIG_CPUMASK_OFFSTACK
 /* Assuming NR_CPUS is huge, a runtime limit is more efficient.  Also,
  * not all bits may be allocated. */
-#define nr_cpumask_bits	nr_cpu_ids
+#define nr_cpumask_bits	((unsigned int)nr_cpu_ids)
 #else
-#define nr_cpumask_bits	NR_CPUS
+#define nr_cpumask_bits	((unsigned int)NR_CPUS)
 #endif
 
 /*