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

David Blaikie via llvm-dev llvm-dev at lists.llvm.org
Sat Jun 30 11:37:35 PDT 2018

I'd suggest approach this like any other bug in source code (not in the
compiler) - reduce the example, isolate the failure - until you either find
a source bug, or a small, standalone example that seems to demonstrate a
contradiction or bug in the way the compiler is interpreting the source.

On Sat, Jun 30, 2018 at 12:49 AM Jeffrey Walton via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> 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
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