[Bug tree-optimization/102769] wrong code at -O1 and above on x86_64-linux-gnu

[zhendong.su at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102769

--- Comment #2 from Zhendong Su <zhendong.su at inf dot ethz.ch> ---
Interesting --- it was missed by clang-10 sanitizers and the CompCert
interpreter (a pretty rare occurrence): 

[565] % ccomp -interp -fall small.c
small.c:13: warning: implicit declaration of function '__builtin_abort' is
invalid in C99 [-Wimplicit-function-declaration]
small.c:13: warning: '__builtin_abort' is declared without a function prototype
Time 114: program terminated (exit code = 0)
[566] % clang-10 -Xclang -disable-llvm-optzns -w -m64 -O0 -fwrapv -ftrapv
-fsanitize=undefined,address small.c; ./a.out
[567] % clang-10 -pie -fPIE -pie -Xclang -disable-llvm-optzns -w -O0 -m64
-fsanitize=memory small.c; ./a.out
[568] %