[Bug tree-optimization/78542] New: [7 Regression] wrong code at -Og results in endless loop

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78542

            Bug ID: 78542
           Summary: [7 Regression] wrong code at -Og results in endless
                    loop
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu
             Build: x86_64-pc-linux-gnu

Created attachment 40157
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40157&action=edit
reduced testcase

Output:
$ x86_64-pc-linux-gnu-gcc -Og testcase.c -Wno-psabi
$ ulimit -t 5
$ ./a.out 
Killed

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-242884-checking-yes-rtl-df-extra-nographite-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--without-cloog --without-ppl --without-isl --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
--with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-242884-checking-yes-rtl-df-extra-nographite-amd64
Thread model: posix
gcc version 7.0.0 20161125 (experimental) (GCC) 

It seems that the "x = 1;" assignment is not present in the generated code.

Tested revisions:
trunk r242884 - FAIL
6-branch r242029 - OK