https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90710
Jeffrey A. Law <law at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2019-06-02
CC| |law at redhat dot com
Ever confirmed|0 |1
--- Comment #1 from Jeffrey A. Law <law at redhat dot com> ---
We focus most of our effort on avoiding false positives with -O2 optimization
levels. As you lower the optimization level (-Og) you will almost certainly
run into these kinds of issues.
Elimination of false positive uninitialized warnings is highly dependent upon
what we call "jump threading". The purpose of jump threading is to realize
that certain paths through the CFG are not possible and to use block copying to
isolate and remove those paths. At lower optimization levels the compiler does
not aggressively thread jumps and thus can leave unexecutable paths in the CFG
which leads to the false positive warning.
The use of builtin_expect can have these effects too as it impacts the cost
analysis done during jump threading to determine the cost/benefit of block
copying to isolate the path.
So confirmed, but not likely something we'll fix in the near future.
