Re: [avr-gcc-list] Weird optimization issue with avr-gcc 4.5.3, re "naked."

[Georg-Johann Lay]

Jan Waclawek schrieb:

> Moreover, in 4.7 it also stores the variable to stack frame even
> without naked, so that could be called a missed
> optimisation/regression.

Thanks for pointing this out. I was lost in all that optimization 
conversation and thought it was an optimization issue from the first post.

There is nothing written like "program crashes because non-existent 
frame used".

So the very problem is that there is a frame needed and there is none 
because of "naked".

Well, that's a bug in the user code, not in the application:
You must not assume that the C code need no frame, even if it is a 
reasonable assumption like here.

However, the frame is really strange and my first suspect is the 
evildoer: -fcaller-saves.

That option causes evil in some places, or let me put things the other 
way round: In some cases -fno-caller-saves can avoid harm like spill 
fails in presence of high register pressure, see PR50925.

Johann