Re: [RFA][PATCH][PR middle-end/59285] BARRIERS and merged blocks

[Jeff Law]

On 01/07/14 01:08, Steven Bosscher wrote:

On Tuesday, January 7, 2014, Jeff Law wrote:

    On 12/24/13 13:19, Steven Bosscher wrote:

        For GCC 4.10

        we should define what behavior should result from
        builtin_unreachable
        (Should it trap? Can it be optimized away after a while to avoid
        these
        unnecessary conditional jumps? ...) but for the moment it seems
        wrong
        IMHO to only optimize this in the cond_exec case and to do so
        against
        the rules of the control flow graph.

    This problem can (and should) be addressed independently of a review
    of the __builtin_unreachable semantics.


Agreed.

:-)

        Something like the patch below, tested with a cross-compiler for
        arm-eabi.
        What do you think of this approach?


                  PR middle-end/59285
                  * ifcvt. (cond_exec_find_if_block): Do not try to
        if-convert an empty
                  basic block without successors due to builtin_unreachable.

    I still prefer my most recent patch.

    jeff



Ok!

Thanks.  One more P1 off the list :-)

jeff