Re: [patch RFA] Fix PR rtl-optimization/35190

["Steven Bosscher" <stevenb dot gcc at gmail dot com>]

xf. http://gcc.gnu.org/ml/gcc-patches/2008-02/msg00587.html

Kaz wrote:
> -	  /* Don't substitute into a non-local goto, this confuses CFG.  */
> +	  /* Don't substitute into a non-local goto, this confuses CFG.
> +	     Since bb-reorder uses indirect jumps for crossing branches
> +	     when the architecture doesn't have unconditional branches
> +	     that can span all of memory, don't touch a jump associated
> +	     with a REG_CROSSING_JUMP note.  */

This seems like just a way to paper over the problem.

If local-alloc makes a substitution that results in a bad insn, then
the validation of the substitution should fail. The SH target specific
code should just not accept this.   Or, you could test for
HAS_LONG_UNCOND_BRANCH like bb-reorder.c does.  There is nothing I see
in this bug report that is limited to hot/cold splitting, you can
probably trigger this bug with a carefully crafted test case. Finally,
it's not clear (at least to me) whether there are other substitutions
that your patch would disable.

Although doing this optimization in local-alloc seems out of place to
begin with...

Oh, and btw, fix_crossing_conditional_branches() is called twice in
bb-reorder.c:fix_edges_for_rarely_executed_code().  This looks like a
merge error.

Gr.
Steven