[Bug tree-optimization/31911] New: Short function (md4) takes very long to compile

["falk at debian dot org" <gcc-bugzilla at gcc dot gnu dot org>]

The attached code (a md4 function, about 100 lines) takes many minutes
(apparently >100) to compile with gcc mainline 4.3 at -O3. At -O2, or with gcc
4.2, it takes below 1 second. 4.3.0 20070411 is OK, too. Memory requirement
stays very low.

The top of a profile with mainline looks like this:

%        symbol name
14.8255  iterative_hash_expr
14.5251  bitmap_find_leader
13.8068  phi_translate
 7.3317  iterative_hash
 6.5265  get_value_handle
 5.3315  htab_find_slot_with_hash
 5.0914  iterative_hash_pointer
 3.8050  iterative_hash_hashval_t
 3.4260  bitmap_set_contains_value
 2.3798  is_gimple_min_invariant
 2.2232  iterative_hash_host_wide_int
 2.0325  tree_operand_length
 1.8615  translate_vuses_through_block
 1.7766  bitmap_bit_p
 1.6062  find_leader_in_sets
 1.5111  expression_for_id
 1.3981  vn_compute
 1.2290  tree_operand_length
 1.0592  expr_pred_trans_eq


-- 
           Summary: Short function (md4) takes very long to compile
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: compile-time-hog
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: falk at debian dot org
 GCC build triplet: alphaev68-unknown-linux-gnu
  GCC host triplet: alphaev68-unknown-linux-gnu
GCC target triplet: alphaev68-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31911