File content as of revision 172:65be27845400:

#ifndef _NRF_DELAY_H
#define _NRF_DELAY_H

#include "nrf.h"

/**
 * @brief Function for delaying execution for number of microseconds.
 *
 * @note NRF52 has instruction cache and because of that delay is not precise.
 *
 * @param number_of_ms
 */
/*lint --e{438, 522} "Variable not used" "Function lacks side-effects" */
#if defined ( __CC_ARM   )

static __ASM void __INLINE nrf_delay_us(uint32_t volatile number_of_us)
{
loop
        SUBS    R0, R0, #1
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
#ifdef NRF52
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
        NOP
#endif
        BNE    loop
        BX     LR
}

#elif defined ( __ICCARM__ )

static void __INLINE nrf_delay_us(uint32_t volatile number_of_us)
{
__ASM (
"loop:\n\t"
       " SUBS R0, R0, #1\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
       " NOP\n\t"
#ifdef NRF52
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
        " NOP\n\t"
#endif
       " BNE.n loop\n\t");
}

#elif defined ( _WIN32 ) || defined ( __unix ) || defined( __APPLE__ )

__STATIC_INLINE void nrf_delay_us(uint32_t volatile number_of_us);

#ifndef CUSTOM_NRF_DELAY_US
__STATIC_INLINE void nrf_delay_us(uint32_t volatile number_of_us)
{}
#endif

#elif defined ( __GNUC__ )

static __INLINE void nrf_delay_us(uint32_t volatile number_of_us) __attribute__((always_inline));
static __INLINE void nrf_delay_us(uint32_t volatile number_of_us)
{
register uint32_t delay __ASM ("r0") = number_of_us;
__ASM volatile (
#if defined(NRF51) && !defined(__ARMCC_VERSION)
        ".syntax unified\n"
#endif
    "1:\n"
    " SUBS %0, %0, #1\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"   
    " NOP\n"  
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
#ifdef NRF52
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
    " NOP\n"
#endif
    " BNE 1b\n"
#if defined(NRF51) && !defined(__ARMCC_VERSION)
    ".syntax divided\n"
#endif
    : "+r" (delay));
}
#endif

void nrf_delay_ms(uint32_t volatile number_of_ms);

#endif