[Bug c/77486] New: ubsan detects runtime error: left shift of negative value -3 at real_hash in real.c:2890

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77486

            Bug ID: 77486
           Summary: ubsan detects runtime error: left shift of negative
                    value -3 at real_hash in real.c:2890
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zeccav at gmail dot com
  Target Milestone: ---

Compiling the following with ubsan sanitized gcc

f(void)
{
 float y=0;
 if(y<0.1) y=1.0;
}

I get

../../gcc-trunk-239945/gcc/real.c:2890:25: runtime error: left shift of
negative value -3

real.c:2890 is " h |= REAL_EXP (r) << 3;"