[PATCH] Remove unreachable gcc_unreachable () at the end of functions

[Richard Biener]

On Sun, 28 Nov 2021, Jeff Law wrote:

> 
> 
> On 11/25/2021 6:33 AM, Richard Biener via Gcc-patches wrote:
> > It seems to be a style to place gcc_unreachable () after a
> > switch that handles all cases with every case returning.
> > Those are unreachable (well, yes!), so they will be elided
> > at CFG construction time and the middle-end will place
> > another __builtin_unreachable "after" them to note the
> > path doesn't lead to a return when the function is not declared
> > void.
> >
> > So IMHO those explicit gcc_unreachable () serve no purpose,
> > if they could be replaced by a comment.  But since all cases
> > cover switches not handling a case or not returning will
> > likely cause some diagnostic to be emitted which is better
> > than running into an ICE only at runtime.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu - any
> > comments?
> >
> > Thanks,
> > Richard.
> >
> > 2021-11-24  Richard Biener  <rguenther@suse.de>
> >
> >  * tree.h (reverse_storage_order_for_component_p): Remove
> >  spurious gcc_unreachable.
> >  * cfganal.c (dfs_find_deadend): Likewise.
> >  * fold-const-call.c (fold_const_logb): Likewise.
> >  (fold_const_significand): Likewise.
> >  * gimple-ssa-store-merging.c (lhs_valid_for_store_merging_p):
> >  Likewise.
> >
> > gcc/c-family/
> >  * c-format.c (check_format_string): Remove spurious
> >  gcc_unreachable.
> They would be a check if someone added a case to the switch that didn't
> return.  But we'd get a return-value warning if that happened.  So I don't see
> that they serve much purpose.

I've pushed the change.

Richard.