using micros() for execution time measurment, can it get "out of order executed"

[ossi]

using micros() for execution time measurment, can it get "out of order executed"

I am using the micros() function to measure the timing of software blocks:

start=micros()
 codeblock
stop=micros()
executionTime=stop-start

Is it possible that the compiler changes the order of execution such that the following is compiled? How is the reordering prevented?

start=micros()
stop=micros()
 codeblock
executionTime=stop-start

If I use a pin that gets toggled at start and stop the compiler sometimes does this reordering. How can I prevent the compiler from rearranging these statements?

 

[PaulStoffregen]

Try this, as a barrier to keep the compiler from reordering stuff.

asm volatile("" : : : "memory");

 

[ossi]

@Paul: Your barrier seems to work. Thanks!
Thank you also for the Teensy boards (especially 4.0)! They have incredible power and Arduino-compatibility makes the start easy.