https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89012
--- Comment #4 from Zach van Rijn <me at zv dot io> ---
The error can be reproduced at `O1` optimization level with both
(strictly both) of the following options:
./cc -c mintest.c -O1 -freorder-blocks-algorithm=stc -ftree-pre
Changing to `-freorder-blocks-algorithm=simple` will not reveal
the issue at `O1`, `O2` or `O3`.
In summary, the only known ways to reproduce this issue are:
(0) `-O2` as described in original bug report;
(1) `-O1 -freorder-blocks-algorithm=stc -ftree-pre`, exclusively
not at any other optimization level;
and the only known ways ot mitigate this issue using either of
the above configurations are:
(2) `-O2 -freorder-blocks-algorithm=simple`;
(3) `-O1` without specifically both of the aforementioned flags.
The attached tarball contains 5 files named by letters 'A' - 'E'
containing the generated assembly, each with -dp` as suggested:
(A) FAIL: `-O2 -freorder-blocks-algorithm=stc`
(B) PASS: `-O2 -freorder-blocks-algorithm=simple`
(C) FAIL: `-O1 -freorder-blocks-algorithm=stc -ftree-pre`
(D) PASS: `-O1 -freorder-blocks-algorithm=simple -ftree-pre`
(E) PASS: `-O1 -freorder-blocks-algorithm=stc`
