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arch: arm: optimize _size_to_mpu_rasr_size function

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This commit optimizes _size_to_mpu_rasr_size(.) in the ARMv7-M
MPU driver, so it makes use of a single _builtin_clz() function
call, instead of two.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
This commit is contained in:
Ioannis Glaropoulos 2018-08-13 10:00:10 +02:00 • committed by Anas Nashif
commit b996955e34
1 changed files with 6 additions and 2 deletions
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8
arch/arm/core/cortex_m/mpu/arm_mpu.c
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@ -103,6 +103,10 @@ static inline u32_t _get_region_attr(u32_t xn, u32_t ap, u32_t tex,
/**
* This internal function converts the region size to
* the SIZE field value of MPU_RASR.
*
* Note: If size is not a power-of-two, it is rounded-up to the next
* power-of-two value, and the returned SIZE field value corresponds
* to that power-of-two value.
*/
static inline u32_t _size_to_mpu_rasr_size(u32_t size)
{
@ -120,8 +124,8 @@ static inline u32_t _size_to_mpu_rasr_size(u32_t size)
return REGION_4G;
}
size = 1 << (32 - __builtin_clz(size - 1));
return (32 - __builtin_clz(size) - 2) << 1;
return ((32 - __builtin_clz(size - 1) - 2 + 1) << MPU_RASR_SIZE_Pos) &
MPU_RASR_SIZE_Msk;
}
/**