https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100503
Bug ID: 100503
Summary: A possible divide by zero problem in function
do_rpo_vn
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: yguoaz at cse dot ust.hk
Target Milestone: ---
In gcc/tree-ssa-sccvn.c, the function do_rpo_vn has the following code (link to
the code location:
https://github.com/gcc-mirror/gcc/blob/releases/gcc-11/gcc/tree-ssa-sccvn.c#L7815-#L7842)
static unsigned
do_rpo_vn (function *fn, edge entry, bitmap exit_bbs,
bool iterate, bool eliminate) {
...
int nex = 0;
...
for (int i = 0; i < n; ++i) {
basic_block bb = BASIC_BLOCK_FOR_FN (fn, rpo[i]);
if (bb->flags & BB_EXECUTABLE)
nex++;
}
...
statistics_histogram_event (cfun, "RPO iterations", 10*nblk / nex);
}
In the loop, the code counts the number of basic blocks with BB_EXECUTABLE flag
in variable nex and use it as divisor after exiting the loop. If no basic block
has such flag, then we will have a divide by zero problem. Is this possible ?
Or we must have at least one bb with the flag BB_EXECUTABLE ?
