GDScript: Blank/comment script lines use up CPU cycles inside for loop

[wyattbiker]

Godot version:
3.2.alpha2 IDE
OS/device including version:
Mac OS X, Mojave

Issue description:
GDScript: Blank/comment script lines use up CPU cycles inside for loop. Seems to be treated like a pass statement. Also the debugger single steps into comments/blank lines (instead of over) which is why I was wondering of the impact.

Steps to reproduce:
Create a Control scene and add script below. Test with blank lines and without blank lines.
For one blank line 1000 iterations on my system I get 185μs vs 148μs. Additional blank/comment lines you add the greater the cpu time.

extends Control
func _ready() -> void:
	var end_time:int
	var x:int = 0
	var start_time:int=OS.get_ticks_usec()
	for i in range(1000):
		
		x += 1
	end_time=OS.get_ticks_usec() 
	print("Elapsed μs: ", end_time - start_time)
	pass # Replace with function body.

[Calinou]

Does this slowdown occur in a project exported in release mode?

[wyattbiker]

I export to a .dmg file which is the installer format for Mac OS X. I install it and run. It has same behaviour. ie CPU cycles are consumed on blank/comments.

Here are the settings. I don't see a specific Release Mode flag.

[bruvzg]

Does this slowdown occur in a project exported in release mode?

I can't reproduce it with release build, only with debug, here are results (average of 5000 runs with 1000 iterations each):

Extra Lines	Release Time	Debug Time
0	53 μs	231 μs
1	52 μs	285 μs
10	52 μs	525 μs
100	52 μs	3011 μs

Edit: Compiled GDScript do preserve tokens for each empty line in any export config.

[bruvzg]

I don't see a specific Release Mode flag.

It's in the corner of file selection dialogue, after you click Export Project.

[wyattbiker]

But yes, blank lines do not take up CPU time when Debug Flag is unchecked. Not as serious, but would be worthwhile pointing out that blanks and comments are treated as 'pass' during dev.

Irrelevant comment: Didn't see that flag on the fileopen dialog. Strange place for it in my opinion.

[Calinou]

Irrelevant comment: Didn't see that flag on the fileopen dialog. Strange place for it in my opinion.

Feel free to suggest improvements in #20219 🙂

[GoDino]

I believe a debugger should not step into blank lines/comments at all. With a small change this could be achieved, which should fix the bug. Would that be ok?
Already have a working version that does this, would be happy to make a PR.

[Calinou]

@GoDino Feel free to open a pull request for this 🙂

[KoBeWi]

Fixed in 4.0