https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92750
Bug ID: 92750
Summary: DSE fails to remove all dead clobbers
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Target Milestone: ---
In PR92645 I see DSE1 doing
MEM[(struct Vec *)&s] = _74;
MEM[(struct Vec *)&a] ={v} {CLOBBER};
- MEM[(struct Vec *)&a] ={v} {CLOBBER};
- MEM[(struct Vec *)&a] ={v} {CLOBBER};
- MEM[(struct Vec *)&a] ={v} {CLOBBER};
- MEM[(struct Vec *)&a] ={v} {CLOBBER};
_73 = (unsigned char) invA_8;
MEM[(struct Vec *)&a].val = _73;
MEM[(struct Vec *)&a + 1B] ={v} {CLOBBER};
MEM[(struct Vec *)&a + 1B].val = _73;
MEM[(struct Vec *)&a + 2B] ={v} {CLOBBER};
- MEM[(struct Vec *)&a + 2B] ={v} {CLOBBER};
MEM[(struct Vec *)&a + 2B].val = _73;
MEM[(struct Vec *)&a + 3B] ={v} {CLOBBER};
MEM[(struct Vec *)&a + 3B].val = _73;
MEM[(struct Vec *)&a + 4B] ={v} {CLOBBER};
- MEM[(struct Vec *)&a + 4B] ={v} {CLOBBER};
- MEM[(struct Vec *)&a + 4B] ={v} {CLOBBER};
MEM[(struct Vec *)&a + 4B].val = _73;
MEM[(struct Vec *)&a + 5B] ={v} {CLOBBER};
...
as you can see it removes all but one clobber but there's still a real must-def
that should make the last clobber dead as well.
