Re: [PATCH 06/12] mode-switching: Tweak entry/exit handling

[Jeff Law <jeffreyalaw@gmail.com>]

On 11/5/23 11:48, Richard Sandiford wrote:
> An entity isn't transparent in a block that requires a specific mode.
> optimize_mode_switching took that into account for normal insns,
> but didn't for the exit block.  Later patches misbehaved because
> of this.
> 
> In contrast, an entity was correctly marked as non-transparent
> in the entry block, but the reasoning seemed a bit convoluted.
> It also referred to a function that no longer exists.
> Since KILL = ~TRANSP, the entity is by definition not transparent
> in a block that defines the entity, so I think we can make it so
> without comment.
> 
> Finally, the exit handling was nested in the entry handling,
> but that doesn't seem necessary.  A target could say that an
> entity is undefined on entry but must be defined on return,
> on a "be liberal in what you accept, be conservative in what
> you do" principle.
> 
> gcc/
> 	* mode-switching.cc (optimize_mode_switching): Mark the exit
> 	block as nontransparent if it requires a specific mode.
> 	Handle the entry and exit mode as sibling rather than nested
> 	concepts.  Remove outdated comment.
OK
jeff