[Bug tree-optimization/78742] New: internal compiler error: in int_cst_value, at tree.c:10782

["dabler at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78742

            Bug ID: 78742
           Summary: internal compiler error: in int_cst_value, at
                    tree.c:10782
           Product: gcc
           Version: 5.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dabler at gmail dot com
  Target Milestone: ---

Created attachment 40283
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40283&action=edit
testcase

On x86_64 Linux:

$ gcc -v -save-temps -O3 -o libmp-test.o libmp.c -c
Using built-in specs.
COLLECT_GCC=gcc
Target: x86_64-linux
Configured with: ../configure --build=x86_64-linux --with-arch=core2
--with-tune=westmere --with-thread=posix --with-as=/usr/bin/as
--with-ld=/usr/bin/ld --with-system-zlib --program-suffix=-5.4
Thread model: posix
gcc version 5.4.0 (GCC)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O3' '-o' 'libmp-test.o' '-c'
'-mtune=westmere' '-march=core2'
 /usr/local/libexec/gcc/x86_64-linux/5.4.0/cc1 -E -quiet -v libmp.c
-mtune=westmere -march=core2 -O3 -fpch-preprocess -o libmp.i
ignoring duplicate directory
"/usr/local/lib/gcc/x86_64-linux/5.4.0/../../../../x86_64-linux/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/lib/gcc/x86_64-linux/5.4.0/include
 /usr/local/include
 /usr/local/lib/gcc/x86_64-linux/5.4.0/include-fixed
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O3' '-o' 'libmp-test.o' '-c'
'-mtune=westmere' '-march=core2'
 /usr/local/libexec/gcc/x86_64-linux/5.4.0/cc1 -fpreprocessed libmp.i -quiet
-dumpbase libmp.c -mtune=westmere -march=core2 -auxbase-strip libmp-test.o -O3
-version -o libmp.s
GNU C11 (GCC) version 5.4.0 (x86_64-linux)
        compiled by GNU C version 5.4.0, GMP version 4.3.1, MPFR version 2.4.1,
MPC version 0.8.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C11 (GCC) version 5.4.0 (x86_64-linux)
        compiled by GNU C version 5.4.0, GMP version 4.3.1, MPFR version 2.4.1,
MPC version 0.8.2
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 6af85bd5d50765bfdcb33ae94df5c82d
libmp.c: In function ‘func’:
libmp.c:3:6: internal compiler error: in int_cst_value, at tree.c:10782
 void func()
      ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

$ cat libmp.c
void foo();

void func()
{
        int m;

        int tab[m];

        __int128 j;
        for(; j; j++)
        {
                tab[j] = 0;
                tab[j+1] = 0;
        }

        foo();
}

Affected gcc versions I have found: 5.x.x, 6.x.x