Screen Glitches every 20 seconds if G++ optimization for Debug turned on

[manto.1]

Why does the screeen glitch for a moment every 20 second when G++ optimization for Debug turned on. If optimization is turned off then it works fine.

[TDK]

If changing the optimization level leads to poor behavior, there is typically a bug in the code somewhere that is causing issues. Poor cache management, and variables not declared as volatile that should be are possible causes.

[manto.1]

Do you have any idea what could produce glitches on regular 20 seconds interval. I disabled all other RTOS tasks and interupts not related to LCD.

[TDK]

You haven't given me much to work with here. What does your program do? What does "glitch" mean exactly? Is the screen actively changing or remaining static? Do you do anything at ~20sec intervals?

[manto.1]

I found out that if I disable instruction cache the glitch disapears. Now the question remains why does the glitch apear when the instruction cache is enabled and optimization for debuging is on in g++.