One last question. Since labelling the variables as volatile has the effect of turning off optimizations related to them,
I tried using __attribute__((const)) on the function to ensure IPA, but the function call still happened. Why couldn't the compiler
optimize these calls away since anyway the function doesn't cause any external effect?
________________________________________
From: Marc Glisse <marc.glisse@xxxxxxxx>
Sent: Sunday, January 23, 2022 11:25 AM
To: Vishal Subramanyam
Cc: gcc-help@xxxxxxxxxxx
Subject: Re: Pure/const function not getting executed as the first operand to logical OR ( || ) (C++)
On Sun, 23 Jan 2022, Vishal Subramanyam via Gcc-help wrote:
> is there a specific name for the type of optimization where the compiler simply decides to drop the return value.
Gcc handles this as part of dead code elimination (among others). A
simpler example would be
int main(){ 1/0; }
which does not crash either.
If you want to make your function func opaque to the optimizers, you may
be interested in __attribute__((noipa)). Using volatile would also avoid
some optimizations.
--
Marc Glisse
