[Bug bootstrap/36908] New: bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[Bug bootstrap/36908] New: bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[tomby at gcc dot gnu dot org]

Bootstrap with BOOT_CFLAGS set to "-O2 -ftree-loop-distribution" runs "forever"
(at least 12 hours then I break compilation). It seems that genautomata in
stage2 run in cycle in merge_states.

configured as:
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ../configure --prefix=/abuild/tbily/install/
--enable-bootstrap --disable-multilib --enable-checks --enable-languages=c,c++
Thread model: posix
gcc version 4.4.0 20080723 (experimental) (GCC)


-- 
           Summary: bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-
                    distribution"
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: bootstrap
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tomby at gcc dot gnu dot org
 GCC build triplet: x86_64-unknown-linux-gnu
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[tomby at gcc dot gnu dot org]

------- Comment #1 from tomby at gcc dot gnu dot org  2008-07-28 11:53 -------
Created an attachment (id=15971)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15971&action=view)
Testcase where loop distribution enabled makes run of binary forever

Compilation with CFLAGS="-O2" and running of testcase is ok (it finish).
Compilation with CLFLAGS="-O2 -ftree-loop-distribution" and running testcase
makes it run forever (last loop cycles). Inlined loop from free_alt_states is
wrongly distributed.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] [4.4 Regression] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[aldot at gcc dot gnu dot org]

-- 

aldot at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
      Known to fail|                            |4.4.0
      Known to work|                            |4.3.1
            Summary|bootstrap forever with      |[4.4 Regression] bootstrap
                   |BOOT_CFLAGS="-O2 -ftree-    |forever with BOOT_CFLAGS="-
                   |loop-distribution"          |O2 -ftree-loop-distribution"
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] [4.4 Regression] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] [4.4 Regression] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2008-08-16 23:36 -------
I don't see why this is a P1, -ftree-loop-distribution is not enabled default
at all.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |build


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] [4.4 Regression] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[jakub at gcc dot gnu dot org]

-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P1                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] [4.4 Regression] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[jakub at gcc dot gnu dot org]

------- Comment #3 from jakub at gcc dot gnu dot org  2008-09-02 16:44 -------
Why got this even marked as regression?  GCC 4.3.1 didn't support
-ftree-loop-distribution, it is a new option, so it can't regress.
The loop in question is:
<bb 8>:
  # state_89 = PHI <state_17(9), state_5(7)>
  # prephitmp.18_6 = PHI <state_89(9), pretmp.17_59(7)>
  state_17 = state_89->next_alt_state;
  state_89->next_alt_state = prephitmp.18_6;
  first_free_alt_state_lsm.29_18 = state_89;
  if (state_17 != 0B)
    goto <bb 9>;
  else
    goto <bb 10>;

<bb 9>:
  goto <bb 8>;
and gets distributed into:
<bb 16>:
  # state_62 = PHI <state_22(17), state_5(7)>
  # prephitmp.18_26 = PHI <state_62(17), pretmp.17_59(7)>
  state_22 = state_62->next_alt_state;
  state_62->next_alt_state = prephitmp.18_26;
  if (state_22 != 0B)
    goto <bb 17>;
  else
    goto <bb 18>;

<bb 17>:
  goto <bb 16>;

<bb 18>:
  # prephitmp.18_90 = PHI <prephitmp.18_26(16)>

<bb 8>:
  # state_89 = PHI <state_17(9), state_5(18)>
  state_17 = state_89->next_alt_state;
  state_89->next_alt_state = prephitmp.18_90;
  first_free_alt_state_lsm.29_18 = state_89;
  if (state_17 != 0B)
    goto <bb 9>;
  else
    goto <bb 10>;

<bb 9>:
  goto <bb 8>;
Perhaps tree-loop-distribution.c is confused by a PHI depending on previous PHI
result?


-- 

jakub at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[jakub at gcc dot gnu dot org]

------- Comment #4 from jakub at gcc dot gnu dot org  2008-10-21 12:51 -------
Dropping [4.4 Regression], as -ftree-loop-distribution is a new option.
Sebastian, can you please look at this?


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.4 Regression] bootstrap  |bootstrap forever with
                   |forever with BOOT_CFLAGS="- |BOOT_CFLAGS="-O2 -ftree-
                   |O2 -ftree-loop-distribution"|loop-distribution"


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[sebpop at gmail dot com]

------- Comment #5 from sebpop at gmail dot com  2008-10-22 21:08 -------
Subject: Re:  bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

> Sebastian, can you please look at this?

Sorry for having missed this bug.  The problem here is that we end
with two identical loops, as we copy almost all the statements in both
loops.  The attached patch solves the problem by counting the number
of memory read and write operations per partition and compares it to
the total number of memory operations in the Reduced Dependence Graph.
Loop distribution is stopped when one of the partitions contains all
the memory ops.

Okay for trunk once it finishes regstrap?

Thanks,
Sebastian


------- Comment #6 from sebpop at gmail dot com  2008-10-22 21:08 -------
Created an attachment (id=16529)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16529&action=view)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[spop at gcc dot gnu dot org]

------- Comment #8 from spop at gcc dot gnu dot org  2008-11-03 16:36 -------
Fixed.


-- 

spop at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908

[Bug bootstrap/36908] bootstrap forever with BOOT_CFLAGS="-O2 -ftree-loop-distribution"

[spop at gcc dot gnu dot org]

------- Comment #7 from spop at gcc dot gnu dot org  2008-11-03 16:36 -------
Subject: Bug 36908

Author: spop
Date: Mon Nov  3 16:35:13 2008
New Revision: 141550

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=141550
Log:
2008-11-03  Sebastian Pop  <sebastian.pop@amd.com>

        PR tree-optimization/36908
        * testsuite/gcc.dg/tree-ssa/pr36908.c: New.
        * tree-loop-distribution.c (number_of_rw_in_rdg): New.
        (number_of_rw_in_partition): New.
        (partition_contains_all_rw): New.
        (ldist_gen): Do not distribute when one of the partitions
        contains all the memory operations.



Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr36908.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-loop-distribution.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36908