Why C++ compiles slowly

[bearophile]

Walter Bright:
> Just for fun, searchfixlist goes back at least to 1983 or so.

It contains this if (I am not able to indent it well):

			if (s->Sseg == p->Lseg &&
                (s->Sclass == SCstatic ||
#if TARGET_LINUX || TARGET_OSX || TARGET_FREEBSD || TARGET_SOLARIS
                (!(config.flags3 & CFG3pic) && s->Sclass == SCglobal)) &&
#else
                  s->Sclass == SCglobal) &&
#endif
                  s->Sxtrnnum == 0 && p->Lflags & CFselfrel) {


How do you rewrite that in good D code? A possible way is to split that messy if into two nested ifs. Between first and second if you define a boolean variable in two different ways using a static if. And in the second if you use the boolean variable and the second part of the runtime test. Something like this:

if (part1) {
	static if (versions_test) {
		bool aux = ...
	} else {
		bool aux = ...	
	}
	
	if (aux && part2) {
		// ...
	} else {
		// ...
	}
}

aux is defined in the middle and not before the first if because performing this runtime test is not necessary when part1 fails.

Bye,
bearophile