[Bug tree-optimization/83325] New: Compile time hog w/ -Os -fwrapv

["asolokha at gmx dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83325

            Bug ID: 83325
           Summary: Compile time hog w/ -Os -fwrapv
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: compile-time-hog
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

Created attachment 42814
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42814&action=edit
Testcase

gcc-8.0.0-alpha20171126 snapshot (r255155) takes indefinite time when compiling
the attached testcase w/ -Os -fwrapv for 32-bit BE powerpc targets (but not for
x86_64 in my setup):

% timeout 20 powerpc-e300c3-linux-gnu-gcc-8.0.0-alpha20171126 -Os -fwrapv -w -c
zxwg8bwp.c
zsh: exit 124   timeout 20 powerpc-e300c3-linux-gnu-gcc-8.0.0-alpha20171126 -Os
-fwrapv -w -c

Some perf top entries:

  13.74%  cc1                           [.] operand_equal_p
  13.20%  cc1                           [.] visit_use
   8.57%  cc1                           [.] hash_table<vn_phi_hasher,
xcallocator>::find_slot_with_hash
   7.17%  cc1                           [.] VN_INFO
   5.49%  cc1                           [.] vn_phi_eq
   4.77%  cc1                           [.] vn_phi_compute_hash
   4.54%  cc1                           [.] inchash::add_expr
   3.61%  cc1                           [.] expressions_equal_p
   3.22%  cc1                           [.] tree_strip_nop_conversions
   3.05%  cc1                           [.] set_ssa_val_to
   2.44%  cc1                           [.] DFS
   2.31%  cc1                           [.] iterative_hash_hashval_t
   2.24%  cc1                           [.] element_precision
   2.03%  cc1                           [.] ssa_undefined_value_p
   1.64%  cc1                           [.] ssa_defined_default_def_p
   1.24%  cc1                           [.] mark_use_processed
   1.17%  cc1                           [.] is_gimple_min_invariant
   1.15%  cc1                           [.] vec<tree_node*, va_heap,
vl_ptr>::safe_grow

gcc 7.2.0 also takes indefinite time when compiling the attached snippet for
x86_64-pc-linux-gnu w/ the same options.

This may be a duplicate of PR82952.