https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103986
Bug ID: 103986
Summary: Miscompilation with -O2 -funswitch-loops and
__builtin_unreachable in ternary operator
Product: gcc
Version: 10.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: daniel at constexpr dot org
Target Milestone: ---
Created attachment 52166
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52166&action=edit
Reduced test case
The loop in the attached reduced test case does not terminate when compiled
with -O3 or -O2 -funswitch-loops with GCC 9.4.0 or GCC 10.3.1 even though it
should only iterate 144 times.
Curiously, the programs works as expected when using an if() instead of the
ternary operator in the assume macro but maybe that's just luck.
I could not reproduce the issue with GCC 8.5.0, GCC 11.2.1 or my GCC 12
checkout from 20220102.
