Compiler efficiency ! ? ! ?

Using Arduino Programming Questions
#1

I am a novice at this and wanted to see just how quickly (or efficiently) the compiler is wrt to, say, a simple pin write function. So I have two super simple sketches (SSS), and I monitor the pin toggle speed with an oscilloscope:

void setup() {
  pinMode(13, OUTPUT); 
}
void loop() {
  digitalWrite(13,HIGH);
  digitalWrite(13,LOW); 
  digitalWrite(13,HIGH);
  digitalWrite(13,LOW); 
}

******** Cycle time = 7.7us.

Now use some simple instructions:

void loop() {
  PORTB |= B00100000;
  PORTB &= B11011111;
  PORTB |=  B00100000;
  PORTB &= B11011111;
}

******** Cycle time = 250ns . . . . that is more than 30X faster . . . 2 cycles each to be exact! Just what you expected. This is not a good indictment if you are looking for any kind of speed. Why is it so bad?

#2

Why is it so bad?

The first code is portable, and it's timing has very little to do with compiler efficiency.
The second is not portable

You have the source - why not take a look?

#3

Look at the code behind digitalWrite, all the checking it does.
Not a compiler issue.

Try this too:

void loop(){
PIND = 0b00100000; // toggle output by writing 1 to input register
}
or
void loop(){
while(1){                   // stay away from (unseen main) calling loop function code
PIND = 0b00100000; // toggle output by writing 1 to input register
}
}
#4

That was way quick guys . . . thanks. I don't know how to examine the code ! :disappointed_relieved: :disappointed_relieved:

#5

hardware/arduino/cores/arduino/wiring_digital.c

#6