[Bug rtl-optimization/61657] Undefined behavior in loop-iv.c

["zeccav at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61657

--- Comment #8 from Vittorio Zecca <zeccav at gmail dot com> ---
Maybe the easiest way to reproduce the issue is as in the following;

gdb ~/local/gcc-5.2.0-sanitized/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/cc1
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Reading symbols from
/home/vitti/local/gcc-5.2.0-sanitized/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/cc1...done.
(gdb) break ../../gcc-5.2.0/gcc/loop-iv.c:2671
Breakpoint 1 at 0x153209e: file ../../gcc-5.2.0/gcc/loop-iv.c, line 2671.
(gdb) run gccerr14.c -O -quiet -funroll-loops
Starting program:
/home/vitti/local/gcc-5.2.0-sanitized/libexec/gcc/x86_64-unknown-linux-gnu/5.2.0/cc1
gccerr14.c -O -quiet -funroll-loops
Missing separate debuginfos, use: debuginfo-install glibc-2.20-8.fc21.x86_64
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Breakpoint 1, iv_number_of_iterations (loop=0x2aaab633f360,
insn=0x2aaab635e400, condition=0x2aaab6362d98, 
    desc=0x7fffffffa810) at ../../gcc-5.2.0/gcc/loop-iv.c:2671
2671              max = (uint64_t) (up - down) / inc + 1;
Missing separate debuginfos, use: debuginfo-install gmp-6.0.0-9.fc21.x86_64
libmpc-1.0.2-3.fc21.x86_64 mpfr-3.1.2-8.fc21.x86_64
(gdb) print up
$1 = 7
(gdb) print down
$2 = -9223372036854775808

But you need an unoptimized version of cc1