[llvm-dev] Determine reason for failure at -O1

[Jeffrey Walton via llvm-dev]

Hi Everyone,

We caught a report for a failed self test when using Clang 5.0 and 6.0
with -DDEBUG and -O1 (i.e., a "debug build"). The code is question is
located at https://github.com/weidai11/cryptopp/blob/master/cham-simd.cpp
. It is the SSSE3 code path for CHAM64.

Other optimizations levels are OK for Clang. GCC, ICC and MSVC are OK.
The code is valgrind, Sanitizer, Coverity and Enterprise Analysis
clean.

An objdump is available at https://pastebin.com/TAKH4eur but it is not
very helpful to me.

My question is, how can we begin to troubleshoot the issue?

Thanks in advance,

Jeff