[Bug target/78246] New: Incorrect vector variable set but not used warning

[zoltan at hidvegi dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78246

            Bug ID: 78246
           Summary: Incorrect vector variable set but not used warning
           Product: gcc
           Version: 6.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zoltan at hidvegi dot com
  Target Milestone: ---

Negating a vector variable can cause incorrect unused variable warning. This
happens both on x86 and PowerPC. Compile with g++ -O2 -S -Wall warning_test.C

Interestingly, compiling this as a C program, the warning disappears. This
happens with compiles as old as gcc-4.8 or as new as gcc-6.2