[Bug tree-optimization/66677] New: [6 Regression] ICE: in vect_transform_stmt, at tree-vect-stmts.c:7626

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66677

            Bug ID: 66677
           Summary: [6 Regression] ICE: in vect_transform_stmt, at
                    tree-vect-stmts.c:7626
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
  Target Milestone: ---

I get the following Firefox build failure during final LTO libxul link: 

/home/trippels/gecko-dev/media/libyuv/source/convert.cc: In function
‘X420ToI420’:
/home/trippels/gecko-dev/media/libyuv/source/convert.cc:239:12: internal
compiler error: in vect_transform_stmt, at tree-vect-stmts.c:7626
 static int X420ToI420(const uint8* src_y,
            ^
0x10a07937 vect_transform_stmt(gimple_statement_base*, gimple_stmt_iterator*,
bool*, _slp_tree*, _slp_instance*)
        ../../gcc/gcc/tree-vect-stmts.c:7625
0x10a2a167 vect_schedule_slp_instance
        ../../gcc/gcc/tree-vect-slp.c:3453
0x10a29ee3 vect_schedule_slp_instance
        ../../gcc/gcc/tree-vect-slp.c:3334
0x10a2a967 vect_schedule_slp(_loop_vec_info*, _bb_vec_info*)
        ../../gcc/gcc/tree-vect-slp.c:3523
0x10a0babb vect_transform_loop(_loop_vec_info*)
        ../../gcc/gcc/tree-vect-loop.c:6223
0x10a2fc8f vectorize_loops()
        ../../gcc/gcc/tree-vectorizer.c:516
0x10916b5b execute
        ../../gcc/gcc/tree-ssa-loop.c:286
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.

I will try to come up with a testcase later.