[Bug rtl-optimization/87985] New: Compile-time and memory hog w/ -O1 -ftree-slp-vectorize

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87985

            Bug ID: 87985
           Summary: Compile-time and memory hog w/ -O1
                    -ftree-slp-vectorize
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: compile-time-hog, memory-hog
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

All gcc versions from the current trunk down to 4.5 branch (where
-ftree-slp-vectorize was introduced) take indefinite time and memory compiling
gcc/testsuite/gcc.dg/pr85180.c at any -O level (except -Og) w/
-ftree-slp-vectorize.

% timeout 10 gcc-9.0.0-alpha20181111 -O1 -ftree-slp-vectorize -c
gcc/testsuite/gcc.dg/pr85180.c
zsh: exit 124   timeout 10 gcc-9.0.0-alpha20181111 -O1 -ftree-slp-vectorize -c

perf top:

Overhead  Shared Objec  Symbol
  56.63%  cc1           [.] operand_equal_p
   7.21%  cc1           [.] tree_operand_check
   6.65%  cc1           [.] tree_strip_nop_conversions
   5.14%  cc1           [.] element_precision
   3.86%  cc1           [.] fold_binary_loc
   2.42%  cc1           [.] split_constant_offset_1
   2.12%  cc1           [.] split_tree
   2.02%  cc1           [.] wide_int_to_tree_1
   1.79%  cc1           [.] generic_simplify_PLUS_EXPR
   1.44%  cc1           [.] split_constant_offset
   1.08%  cc1           [.] build2
   0.93%  cc1           [.] ggc_internal_alloc
   0.83%  cc1           [.] integer_zerop
   0.83%  cc1           [.] build_int_cst
   0.55%  cc1           [.] tree_swap_operands_p
   0.50%  cc1           [.] canonize
   0.50%  cc1           [.] commutative_tree_code

It's even not necessary to leave ten Zs, as the issue is reproducible w/ as
"low" as two Ys.