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Implement fast log2

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This commit is contained in:
KarateBrot 2022-10-15 16:50:10 +02:00
parent cd2a259b14
commit 32480cf002
2 changed files with 4 additions and 2 deletions
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2
src/main/common/utils.h
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@ -100,6 +100,8 @@ http://resnet.uoregon.edu/~gurney_j/jmpc/bitwise.html
static inline int16_t cmp16(uint16_t a, uint16_t b) { return (int16_t)(a-b); }
static inline int32_t cmp32(uint32_t a, uint32_t b) { return (int32_t)(a-b); }
static inline uint32_t llog2(uint32_t n) { return 31 - __builtin_clz(n | 1); }
// using memcpy_fn will force memcpy function call, instead of inlining it. In most cases function call takes fewer instructions
// than inlined version (inlining is cheaper for very small moves < 8 bytes / 2 store instructions)
#if defined(UNIT_TEST) || defined(SIMULATOR_BUILD)

4
src/main/drivers/accgyro/accgyro_spi_icm426xx.c
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@ -31,7 +31,7 @@
#if defined(USE_GYRO_SPI_ICM42605) || defined(USE_GYRO_SPI_ICM42688P)
#include "common/axis.h"
#include "common/maths.h"
#include "common/utils.h"
#include "build/debug.h"
#include "drivers/accgyro/accgyro.h"
@ -208,7 +208,7 @@ void icm426xxGyroInit(gyroDev_t *gyro)
// Get desired output data rate
uint8_t odrConfig;
const uint8_t decim = LOG2_8BIT(gyro->mpuDividerDrops + 1);
const unsigned decim = llog2(gyro->mpuDividerDrops + 1);
if (gyro->gyroRateKHz && decim < ODR_CONFIG_COUNT) {
odrConfig = odrLUT[decim];
} else {