https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101555
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, so most of the time is spent in ANTIC compute, specifically PHI translation
and there translate_vuse_through_block doing the (rate limited)
stmt_may_clobber_ref_p_1 query.
It's a bit fishy that we're doing these things "twice", in particular
we are supposed to translate ANTIC_IN to the predecessor ANTIC_OUT, thus
all VUSEs should be already top-of-block. But then in compute_antic_aux
we're doing
/* Prune expressions that are clobbered in block and thus become
invalid if translated from ANTIC_OUT to ANTIC_IN. */
prune_clobbered_mems (ANTIC_OUT, block);
which is supposed to do the "translation" through the block but that does
not adjust VUSEs of expressions. That uses value_dies_in_block_x, something
with a cache but also following a somewhat different logic with respect
to the VUSEs in the expression.
The main complication here is that the expression set we start from is
taken from the VN tables which may put "pre-translated" VUSEs in rather
than starting with the VUSEs as they were.
