[Bug middle-end/50200] New: ICE: SIGSEGV in df_insn_refs_collect (df-scan.c:3405)

["zsojka at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50200

             Bug #: 50200
           Summary: ICE: SIGSEGV in df_insn_refs_collect (df-scan.c:3405)
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: zsojka@seznam.cz
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu


Created attachment 25112
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25112
reduced testcase

Compiler output:
$ gcc -O -fno-tree-ch -fno-tree-dominator-opts -fno-tree-loop-optimize
-funroll-loops --param case-values-threshold=1 testcase.c
==27091== Invalid read of size 8
==27091==    at 0x6C5887: df_insn_refs_collect(df_collection_rec*,
basic_block_def*, df_insn_info*) (df-scan.c:3405)
==27091==    by 0x6C643A: df_insn_refs_verify(df_collection_rec*,
basic_block_def*, rtx_def*, bool) (df-scan.c:4343)
==27091==    by 0x6C67AA: df_bb_verify(basic_block_def*) (df-scan.c:4392)
==27091==    by 0x6C9081: df_scan_verify() (df-scan.c:4526)
==27091==    by 0x6B2A88: df_verify() (df-core.c:1644)
==27091==    by 0x6B2BBE: df_analyze() (df-core.c:1205)
==27091==    by 0x113E039: rest_of_handle_initialize_regs() (init-regs.c:60)
==27091==    by 0x8E6216: execute_one_pass(opt_pass*) (passes.c:2063)
==27091==    by 0x8E6584: execute_pass_list(opt_pass*) (passes.c:2118)
==27091==    by 0x8E6596: execute_pass_list(opt_pass*) (passes.c:2119)
==27091==    by 0xA3E87D: tree_rest_of_compilation(tree_node*)
(tree-optimize.c:420)
==27091==    by 0x6936B5: cgraph_expand_function(cgraph_node*)
(cgraphunit.c:1797)
==27091==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==27091== 
testcase.c: In function 'check':
testcase.c:22:1: internal compiler error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

Tested revisions:
r178096 - crash
r177543 - crash