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

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

[falk at debian 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


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           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

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

[falk at debian dot org]

------- Comment #1 from falk at debian dot org  2007-05-13 13:49 -------
Created an attachment (id=13546)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13546&action=view)
Test case


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

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

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2007-05-13 14:12 -------
Confirmed.  A PRE problem.  There's a lot in PA_IN[3].


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dberlin at gcc dot gnu dot
                   |                            |org


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

[Bug tree-optimization/31911] [4.3 Regression] Short function (md4) takes very long to compile

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2007-05-13 14:15:06
               date|                            |
            Summary|Short function (md4) takes  |[4.3 Regression] Short
                   |very long to compile        |function (md4) takes very
                   |                            |long to compile
   Target Milestone|---                         |4.3.0


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

[Bug tree-optimization/31911] [4.3 Regression] Short function (md4) takes very long to compile

[dberlin at gcc dot gnu dot org]

------- Comment #3 from dberlin at gcc dot gnu dot org  2007-05-13 16:00 -------
How interesting.  It  is considering performing insertion on an expression that
ends up having to phi translate back through 1000's of other value handles.

But it should have already solved these, so i'm not sure why they aren't
cached.


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

[Bug tree-optimization/31911] [4.3 Regression] Short function (md4) takes very long to compile

[dberlin at gcc dot gnu dot org]

------- Comment #5 from dberlin at gcc dot gnu dot org  2007-05-13 22:52 -------
Fixed


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dberlin at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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

[Bug tree-optimization/31911] [4.3 Regression] Short function (md4) takes very long to compile

[dberlin at gcc dot gnu dot org]

------- Comment #4 from dberlin at gcc dot gnu dot org  2007-05-13 22:52 -------
Subject: Bug 31911

Author: dberlin
Date: Sun May 13 21:52:10 2007
New Revision: 124657

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=124657
Log:
2007-05-13  Daniel Berlin  <dberlin@dberlin.org>

        Fix PR tree-optimization/31911
        * tree-ssa-pre.c (phi_translate): Make sure to cache results even
        if they didn't change the expression.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-ssa-pre.c


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