[Bug other/66827] New: [6 Regression] left shifts of negative value warnings due to C++14 switch

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66827

            Bug ID: 66827
           Summary: [6 Regression] left shifts of negative value warnings
                    due to C++14 switch
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
  Target Milestone: ---

For C++98 -fsanitize=undefined didn't warn in case of left shifts of negative
values.
Now that trunk switched to C++14 a number of new warnings popped up:

gcc/config/rs6000/rs6000.c:5398:36: runtime error: left shift of negative value
-12301
gcc/config/rs6000/rs6000.md:3126:17: runtime error: left shift of negative
value -1
gcc/dce.c:287:16: runtime error: ../../gcc/gcc/haifa-sched.c:1442:26:left shift
of negative value -1
gcc/expmed.c:3002:15: runtime error: left shift of negative value -1
gcc/haifa-sched.c:1164:24: runtime error: left shift of negative value -1
gcc/haifa-sched.c:1442:26: runtime error: left shift of negative value -1
gcc/hwint.h:250:19: runtime error: left shift of negative value -1000013824
gcc/real.c:2861:25: runtime error: left shift of negative value -63
gcc/sched-deps.c:112:20: runtime error: left shift of negative value -1
gcc/sreal.c:231:20: runtime error: left shift of negative value -1092263868
libcpp/files.c:683:30: runtime error: left shift of negative value -1
libiberty/regex.c:6970:11: runtime error: left shift of negative value -1
libiberty/regex.c:7165:4: runtime error: left shift of negative value -1