delayNanoseconds returns too early

[slenius]

Board: Teensy 4.1
Arduino: 1.8.19
Teensyduino: 1.56
All options default

When you call delayNanoseconds(x) where x > ~470000, it returns early. I suspect there's an overflow with this line:

uint32_t cycles =   ((F_CPU_ACTUAL>>16) * nsec) / (1000000000UL>>16);

delayNanoseconds(460000) -> cycles = 276006
delayNanoseconds(470000) -> cycles = 516

Complete code that illustrates problem:

#include <stdint.h>


void setup() {
  Serial.begin(9600);
}

static constexpr int n_loops = 10000;
static int i = 0;

static uint32_t start_time_micros, end_time_micros, delta_time_micros, delay_micros, delay_nanos;


void loop() {
  if(i == 0){
    Serial.printf("Start test...\n");
  }
  if(i < n_loops){
    delay_micros = max(i, 1);
    delay_nanos = delay_micros * 1000;
    start_time_micros = micros();
    //delayMicroseconds(delay_micros); // This test passes
    delayNanoseconds(delay_nanos); // This test fails
    end_time_micros = micros();
    delta_time_micros = end_time_micros - start_time_micros;
  
    if (delta_time_micros < (delay_micros - 1)){
      Serial.printf("delay_micros = %d us\tdelta_time_micros = %lu us\n", delay_micros, delta_time_micros);
    }
  }
  if(i == n_loops){
    Serial.printf("Done!\n");
  }
  i++;
}