[Bug tree-optimization/59757] Unexpected VN_TOP in SSCVN

[joey.ye at arm dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59757

--- Comment #1 from Joey Ye <joey.ye at arm dot com> ---
foo.c: In function 'univision_ug2828gfeff01_init':
foo.c:119:1: internal compiler error: tree check: expected ssa_name, have
var_de
cl in vn_reference_compute_hash, at tree-ssa-sccvn.c:631
 univision_ug2828gfeff01_init(CTL_GFX_SEP_DRIVER_t *d, int depth)

Traced to SSCVN:
Breakpoint 1, vn_reference_compute_hash (vr1=0x798fa94)
    at /xxx/src/gcc/gcc/tree-ssa-sccvn.c:598
598     in /xxx/src/gcc/gcc/tree-ssa-sccvn.c

Backtrace is 
vn_reference_lookup

(gdb) call debug_tree(vr1->vuse)
 <var_decl 0x8fe4ba0 vn_top.15
    type <void_type 0x89c08a0 void VOID
        align 8 symtab 0 alias set -1 canonical type 0x89c08a0
        pointer_to_this <pointer_type 0x89c0900>>
    used ignored VOID file foo.c line 119 col 1
    align 8>

(gdb) call debug_tree(VN_TOP)
 <var_decl 0x8fe4ba0 vn_top.15
    type <void_type 0x89c08a0 void VOID
        align 8 symtab 0 alias set -1 canonical type 0x89c08a0
        pointer_to_this <pointer_type 0x89c0900>>
    used ignored VOID file foo.c line 119 col 1
    align 8>

For some reason vr1->vuse is VN_TOP, which is unexpected. But I couldn't go
further without understanding SCCVN.

Anyone can help?