Some function call could be removed by their value

[Dräc]

I try to express a think shared by several people.
Some function call could be removed by their value.

For example:
RGB(255,0,0) is equivalent in #FF0000

Even if RGB() is a function, given x,y,z (means x,y and z are constants) RGB(x,y,z) is a given value too.

So, a possible optimisation could be removing a function call by its value according to:
- the entries are constants
- the value retrieved by the function is a constant too.

[PB]

I don't know what you mean? But when the compiler sees RGB(255,0,0) in
your source, it's replaced by #FF0000 in the executable; in other words,
putting RGB(255,0,0) in your code is the same as putting a constant in
your code with the value #FF0000.

[Dräc]

Sure?

Code: Select all

; a = RGB(255,0,0)
	PUSH	 dword 0
	PUSH	 dword 0
	MOV	 eax,255
	CALL	 PB_RGB
	MOV	 dword [v_a],eax

[Dräc]

correction: RGB(255,0,0) <-> #FF

[PB]

I was going by something Fred once told me about Chr(), that using Chr('a')
would just put 65 in the code directly like a constant, but maybe I didn't
understand him correctly.

[tinman]

That's if you do something like

Code: Select all

b.s = "Foo"+Chr(65)+"wibble"

Then it will generate the string in the executable rather than have to perform string concatenation.

Similarly,

Code: Select all

b.s = Chr(65)

by itself will create an "A" in your executable so there is no call to a Chr() function and b will take a copy of the string from your exe.

[freak]

PB:
That is correct, but it only applies to the Chr() function because this is very
frequently used with constant values as input.

Dräc:
Just overwrite the PB function with a macro...

Code: Select all

Macro RGB(r, g, b)
 (((b) << 16) | ((g) << 8) | (r))
EndMacro

; a = RGB(255,0,0)
  MOV    dword [v_a],255

[PB]

Ah, so I did understand it right, but it's just for Chr(). I thought all commands
would do it, too. So I guess that's what Dräc is wishing for, then?

[Dräc]

@PB: right

@freak : of course it is one solution for RGB(). But my naive suggestion is for a systematic approach of the compiler applicable to most functions of the PB standard library…