On 12/16/2016 06:57 AM, Richard Biener wrote:
On Fri, Dec 16, 2016 at 2:54 AM, Jeff Law <l...@redhat.com> wrote:
+ /* REF is a memory write. Go ahead and get its base, size, extent
+ information and encode the bytes written into LIVE_BYTES. We can
+ handle any case where we have a known base and maximum size.
+
+ However, experimentation has shown that bit level tracking is not
+ useful in practice, so we only track at the byte level.
+
+ Furthermore, experimentation has shown that 99% of the cases
+ that require byte tracking are 64 bytes or less. */
+ if (valid_ao_ref_for_dse (ref)
+ && (ref->max_size / BITS_PER_UNIT
+ <= PARAM_VALUE (PARAM_DSE_MAX_OBJECT_SIZE)))
+ {
+ live_bytes = BITMAP_ALLOC (NULL);
+ orig_live_bytes = BITMAP_ALLOC (NULL);
+ bitmap_set_range (live_bytes,
+ ref->offset / BITS_PER_UNIT,
+ ref->max_size / BITS_PER_UNIT);
+ bitmap_copy (orig_live_bytes, live_bytes);
So I'd use a once-per-pass allocated sbitmap here. I don't see why you need
the orig_live_bytes bitmap though (just keep that implicitely by the known
range?)
So if we use a once-per-pass allocated bitmap, that actually facilitates
returning a tri-state from dse_possible_dead_store_p and moving the
trimming into dse_optimize_stmt.
ORIG_LIVE_BYTES was more convenience than anything -- we want it so that
we can compute the dead bytes for trimming. But we can certainly
compute it on-demand at that time.
Jeff
