On Mon, Jul 31, 2017 at 4:36 PM, Luc Van Oostenryck
<luc.vanoostenryck@xxxxxxxxx> wrote:
>
> Fix this by:
> 1) refuse to emit the "crazy programmer" warning if there
> is a potential dead BB
> 2) move kill_unreachable_bbs() in the main cleanup loop
> which will avoid nested ep->bbs loop.
Great!
>
> Note: this solution is preferable to some others because
> the "crazy programmer" condition happens very rarely.
> It this thus better to delay this check than to call
> kill_unreachable_bbs() preventively.
>
> Note: the reproducer is one with very broken syntax but nothing
> forbid the same situation to happen with a valid program.
>
> Fixes: 51cfbc90a5e1462fcd624a1598ecd985a508a5d6
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
> ---
> cse.c | 2 ++
> flow.c | 2 --
> linearize.c | 3 ---
> simplify.c | 9 +++++++++
> validation/crash-ptrlist.c | 23 +++++++++++++++++++++++
> validation/crazy02-not-so.c | 18 ++++++++++++++++++
> 6 files changed, 52 insertions(+), 5 deletions(-)
> create mode 100644 validation/crash-ptrlist.c
>
> diff --git a/cse.c b/cse.c
> index 0d3815c5a..17b3da01a 100644
> --- a/cse.c
> +++ b/cse.c
> @@ -364,6 +364,8 @@ void cleanup_and_cse(struct entrypoint *ep)
> repeat:
> repeat_phase = 0;
> clean_up_insns(ep);
> + if (repeat_phase & REPEAT_CFG_CLEANUP)
> + kill_unreachable_bbs(ep);
> for (i = 0; i < INSN_HASH_SIZE; i++) {
Interesting. So my reading is that, this is similar to the other
alternative patch
we discuss with different that:
1. move up kill_unreachable_bbs(ep) right after clean_up_insns(ep)
> + /*
> + * If some BB have been removed it is possible that this
> + * memop is in fact part of a dead BB. In this case
> + * we must not warn since nothing is wrong.
> + * If not part of a dead BB this will be redone after
> + * the BBs have been cleaned up.
> + */
> + if (repeat_phase & REPEAT_CFG_CLEANUP)
> + return 0;
2. Avoid issue "crazy programmer" if we still have dead code to clean up.
That sound very reasonable and I feel that is better than the previous version
which eager to kill bbs. That is great.
I really appreciate the change.
Chris
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