Re: [PATCH v4 4/8] rt2800: fix registers init for MT7620

[Stanislaw Gruszka <sgruszka@redhat.com>]

On Tue, Oct 16, 2018 at 01:19:52PM +0200, Felix Fietkau wrote:
> > I have no idea how this could be related. But I think I found
> > somewhat reasonable explenation where the problem is.
> > I think below code :
> > 
> > 	if (a || b || c) {
> > 		CODE1();
> > 	} else if (c) {
> > 		CODE2();
> > 	}
> > 
> > can not be deterministic and can be compiled differently depending
> > on compiler version and used options. Sometimes it could result
> > in this 
> > 
> > 	if (a || b || c) {
> > 		CODE1();
> > 	}
> > 
> > and sometimes in this:
> > 
> > 	if (a || b) {
> > 		CODE1();
> > 	} else if (c) {
> > 		CODE2();
> > 	}
> > 
> > So that would explain the problems you see. And indeed patch
> > could cause regression on systems where second variant of
> > initalizing RT6352 registers was used.
> I don't see how that can be non-deterministic at all. The 'else if' part
> can only be hit if the first if did not match.

I meant non-deterministic during compilation process, when compiler
do or do not some optimizations or if compiler version differs.

Regards
Stanislaw