https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85588
Bug ID: 85588
Summary: -fwrapv miscompilation
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: kristerw at gcc dot gnu.org
Target Milestone: ---
GCC miscompiles gcc/testsuite/gcc.dg/torture/pr57656.c when using -fwrapv
> gcc -fwrapv pr57656.c
> ./a.out
Abort (core dumped)
The problem seems to be exactly the same as in PR57656 (but when using
-fwrapv):
t = 1 - ((a - b) / c);
is changed to
t = (b - a) / c + 1;
which is not the same in this case where both (a - b) and (b - a) have the
value 0x80000000.
This fails in GCC 6 and newer versions. Compiling using GCC 5 produces the
correct result.
