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common: Add __fls function

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Returns the most significant bit set.
Replace 31 - __builtin_clz(x), so x must be different from 0.
Use get_next_bit when not on the performance path,
on performance path set the bit field just after reading it.

BRANCH=smaug
BUG=none
TEST=compile, check Ryu still works.

Change-Id: Ie1a4cda4188f45b4bf92d0549d5c8fb401a30e5d
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/301300
This commit is contained in:
Gwendal Grignou
2015-09-19 10:48:19 -07:00
committed by chrome-bot
parent dbfb5c1dee
commit 1d8fcfcd0d
7 changed files with 16 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
chip/npcx/flash.c
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@@ -292,7 +292,7 @@ static int protect_to_reg(unsigned int start, unsigned int len,
blocks = len / size;
/* Determine bp = log2(blocks) with log2(0) = 0 */
bp = blocks ? (31 - __builtin_clz(blocks)) : 0;
bp = blocks ? __fls(blocks) : 0;
/* Clear bits */
*sr1 &= ~(SPI_FLASH_SR1_SEC | SPI_FLASH_SR1_TB

2
common/timer.c
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@@ -65,8 +65,8 @@ void process_timers(int overflow)
/* read atomically the current state of timer running */
check_timer = running_t0 = timer_running;
while (check_timer) {
int tskid = 31 - __builtin_clz(check_timer);
int tskid = __fls(check_timer);
/* timer has expired ? */
if (timer_deadline[tskid].val <= now.val)
expire_timer(tskid);

6
core/cortex-m/task.c
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@@ -266,7 +266,7 @@ void svc_handler(int desched, task_id_t resched)
tasks_ready |= 1 << resched;
ASSERT(tasks_ready);
next = __task_id_to_ptr(31 - __builtin_clz(tasks_ready));
next = __task_id_to_ptr(__fls(tasks_ready));
#ifdef CONFIG_TASK_PROFILING
/* Track time in interrupts */
@@ -536,11 +536,11 @@ void mutex_unlock(struct mutex *mtx)
: "r" (&mtx->lock), "r" (&mtx->waiters), "r" (0)
: "cc");
while (waiters) {
task_id_t id = 31 - __builtin_clz(waiters);
task_id_t id = __fls(waiters);
waiters &= ~(1 << id);
/* Somebody is waiting on the mutex */
task_set_event(id, TASK_EVENT_MUTEX, 0);
waiters &= ~(1 << id);
}
/* Ensure no event is remaining from mutex wake-up */

6
core/cortex-m0/task.c
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@@ -231,7 +231,7 @@ task_ __attribute__((noinline)) *__svc_handler(int desched, task_id_t resched)
tasks_ready |= 1 << resched;
ASSERT(tasks_ready);
next = __task_id_to_ptr(31 - __builtin_clz(tasks_ready));
next = __task_id_to_ptr(__fls(tasks_ready));
#ifdef CONFIG_TASK_PROFILING
/* Track additional time in re-sched exception context */
@@ -530,11 +530,11 @@ void mutex_unlock(struct mutex *mtx)
: "r" (&mtx->lock), "r" (&mtx->waiters), "r" (0)
: "cc");
while (waiters) {
task_id_t id = 31 - __builtin_clz(waiters);
task_id_t id = __fls(waiters);
waiters &= ~(1 << id);
/* Somebody is waiting on the mutex */
task_set_event(id, TASK_EVENT_MUTEX, 0);
waiters &= ~(1 << id);
}
/* Ensure no event is remaining from mutex wake-up */

6
core/nds32/task.c
View File

@@ -272,7 +272,7 @@ void syscall_handler(int desched, task_id_t resched, int swirq)
task_ *next_sched_task(void)
{
return __task_id_to_ptr(31 - __builtin_clz(tasks_ready));
return __task_id_to_ptr(__fls(tasks_ready));
}
static inline void __schedule(int desched, int resched, int swirq)
@@ -453,11 +453,11 @@ void mutex_unlock(struct mutex *mtx)
mtx->lock = 0;
while (waiters) {
task_id_t id = 31 - __builtin_clz(waiters);
task_id_t id = __fls(waiters);
waiters &= ~(1 << id);
/* Somebody is waiting on the mutex */
task_set_event(id, TASK_EVENT_MUTEX, 0);
waiters &= ~(1 << id);
}
/* Ensure no event is remaining from mutex wake-up */

2
include/gpio.h
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@@ -47,7 +47,7 @@
#define GPIO_INT_BOTH_DSLEEP (GPIO_INT_BOTH | GPIO_INT_DSLEEP)
/* Convert GPIO mask to GPIO number / index. */
#define GPIO_MASK_TO_NUM(mask) (31 - __builtin_clz(mask))
#define GPIO_MASK_TO_NUM(mask) (__fls(mask))
/* Convert a GPIO to a port + mask pair */
#define GPIO_TO_PORT_MASK_PAIR(gpio) \

5
include/util.h
View File

@@ -77,7 +77,10 @@
/* True of x is a power of two */
#define POWER_OF_TWO(x) (x && !(x & (x - 1)))
/**
/* find the most significant bit. Not defined in n == 0. */
#define __fls(n) (31 - __builtin_clz(n))
/*
* macros for integer division with various rounding variants
* default integer division rounds down.
*/