AVR/GCC bug?

Test.ino

// NeoPixel Ring simple sketch (c) 2013 Shae Erisson
// released under the GPLv3 license to match the rest of the AdaFruit NeoPixel library

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
#include <avr/power.h>
#endif

// Which pin on the Arduino is connected to the NeoPixels?
// On a Trinket or Gemma we suggest changing this to 1
#define PIN            PB3

// How many NeoPixels are attached to the Arduino?
#define NUMPIXELS      24

// When we setup the NeoPixel library, we tell it how many pixels, and which pin to use to send signals.
// Note that for older NeoPixel strips you might need to change the third parameter--see the strandtest
// example for more information on possible values.
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

int phase = 0;
int direction = 1;

void setup() {
  // This is for Trinket 5V 16MHz, you can remove these three lines if you are not using a Trinket
#if defined (__AVR_ATtiny85__)
  if (F_CPU == 16000000) clock_prescale_set(clock_div_1);
#endif
  // End of trinket special code

  pixels.begin();
  pixels.setBrightness(8);
  pixels.show();
}

void hexdump(uint32_t value) {
  for (int i = 0; i < 12; ++i) {
    pixels.setPixelColor(i+12, 0, 0, ((value >> i) & 1) * 255);
  }
}

// I'd like to use a global variable but the program does not work when I
// *write* to to. If I only read it everything is fine.
// uint8_t kitt[12];

void loop()
{
  // Instead, I need to use a stack variable.
  uint8_t kitt[12];

  for (int k = 0; k < 24; k++) {
    for (int i = 0; i < 12; i++) {
      kitt[i] /= 2;
    }

    kitt[phase] = 255;

    if (phase == 0) {
      direction = 1;
    } else if (phase == 11) {
      direction = -1;
    }
    phase += direction;

    for (int i = 0; i < 12; i++) {
      pixels.setPixelColor(i, 0, kitt[i], 0);
      pixels.setPixelColor(23-i, kitt[i], 0, 0);
    }

    pixels.show();
    delay(150);
  }
}