Re: [PATCH] Fix DCE REG_LIBCALL note moving from noop move insns (PR rtl-optimization/33644)

[kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)]

> Now, to the design issue at hand.  REG_LIBCALL_ID seems a better way to
> represent libcalls than the longstanding begin/end structure for the
> reason Danny stated: you can tell what instruction is in what libcall
> without walking around in the instruction stream.  So, we don't want to
> be removing it, we want to be moving towards it.

For what it's worth, I agree.  It has always been a nuisance that we
had such a poor structure to represent this and has always been the source
of confusion in the past.

> But, because we're presently dependent on the old structures, it sounds
> to me like we need to make sure that no non-libcall instructions are
> inserted between REG_LIBCALL and REG_RETVAL.  That's the bug.  

I agree with this as well.