https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38474
--- Comment #89 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fallout includes
FAIL: g++.dg/opt/store-merging-1.C scan-tree-dump store-merging "New sequence
of [12] stores to replace old one of 2 stores"
which shows
Starting new chain with statement:
s ={v} {CLOBBER};
The base object is:
&s
Recording immediate store from stmt:
s.a = 0;
Recording immediate store from stmt:
s.b = 0;
stmt causes chain termination:
foo (s);
and the CLOBBER allows us to use zeros for padding:
Store 0:
bitsize:64 bitpos:0 val:{CLOBBER}
Store 1:
bitsize:32 bitpos:0 val:0
Store 2:
bitsize:8 bitpos:32 val:0
After writing {CLOBBER} of size 64 at position 0
the merged value contains 00 00 00 00 00 00 00 00
the merged mask contains 00 00 00 00 00 00 00 00
After writing 0 of size 32 at position 0
the merged value contains 00 00 00 00 00 00 00 00
the merged mask contains 00 00 00 00 00 00 00 00
After writing 0 of size 8 at position 32
the merged value contains 00 00 00 00 00 00 00 00
the merged mask contains 00 00 00 00 00 00 00 00
Coalescing successful!
Merged into 1 stores
New sequence of 1 stores to replace old one of 2 stores
# .MEM_6 = VDEF <.MEM_5>
MEM <unsigned long> [(void *)&s] = 0;
Merging successful!
