[Bug optimization/15255] New: [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[Bug optimization/15255] New: [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[kazu at cs dot umass dot edu]

int
foo (int a)
{
  return a * 2 + a * 2;
}

The last SSA form looks like:

foo (a)
{
  int T.0;

<bb 0>:
  T.0_2 = a_1 + a_1;
  return T.0_2 * 2;

}

Why not return a_1 * 4?

Interestingly, a * 3 + a * 5 is converted to a * 8, but if I compute like so

int
foo (int a)
{
  int b = a * 3;
  int c = a * 5;
  return b + c;
}

I get:

  b_2 = a_1 * 3;
  c_3 = a_1 * 5;
  return b_2 + c_3;

-- 
           Summary: [tree-ssa] a * 2 + a * 2 is not converted to a * 4
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Keywords: pessimizes-code
          Severity: enhancement
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kazu at cs dot umass dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-03 11:24 -------
Confirmed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-03 11:24:24
               date|                            |
   Target Milestone|---                         |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-24 01:26 -------
Mine as this will get fixed when 15459 gets fixed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |pinskia at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-24 15:57 -------
The first one is because fold converted it to be (a + a) * 2 but fold should be doing this conversion.  PR 
15459 fixes the other problem in the PR, I will submitting a new patch today with more comments and 
more like the RTL combiner. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.5.0                       |---


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-06-21 05:13 -------
I will submit my patch tree combine patch tonight which fixes the second case but not the first as the 
first is a problem in fold.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-02-15 22:22 -------
As I said before I was not going to fix a fold problem (for the first testcase).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|pinskia at gcc dot gnu dot  |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|ASSIGNED                    |NEW


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255
Bug 15255 depends on bug 15459, which changed state.

Bug 15459 Summary: [meta-bug] there should be a tree combiner like the rtl one
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=15459

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

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2008-08-13 09:00 -------
Fixed.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[rguenth at gcc dot gnu dot org]

------- Comment #11 from rguenth at gcc dot gnu dot org  2008-08-13 08:58 -------
Subject: Bug 15255

Author: rguenth
Date: Wed Aug 13 08:57:20 2008
New Revision: 139048

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=139048
Log:
2008-08-13  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/15255
        * tree-ssa-reassoc.c (linearize_expr_tree): Declare.
        (struct oecount_s): New struct and VEC types.
        (cvec): New global.
        (oecount_hash): New function.
        (oecount_eq): Likewise.
        (oecount_cmp): Likewise.
        (zero_one_operation): New function.
        (build_and_add_sum): Likewise.
        (undistribute_ops_list): Perform un-distribution of multiplication
        and division on the chain of summands.
        (should_break_up_subtract): Also break up subtracts for factors.
        (reassociate_bb): Delete dead visited statements.
        Call undistribute_ops_list.  Re-sort and optimize if it did something.
        * passes.c (init_optimization_passes): Move DSE before
        reassociation.
        * tree-ssa-loop-niter.c (stmt_dominates_stmt_p): Correctly handle
        PHI nodes.

        * gcc.dg/tree-ssa/reassoc-14.c: New testcase.
        * gcc.dg/tree-ssa/reassoc-15.c: Likewise.
        * gcc.dg/tree-ssa/reassoc-16.c: Likewise.
        * gcc.dg/torture/reassoc-1.c: Likewise.
        * gcc.dg/tree-ssa/recip-2.c: Adjust.
        * gcc.dg/tree-ssa/recip-6.c: Likewise.
        * gcc.dg/tree-ssa/recip-7.c: Likewise.
        * gfortran.dg/reassoc_4.f: Likewise.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/reassoc-1.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/reassoc-14.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/reassoc-15.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/reassoc-16.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/reassoc-17.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/reassoc-18.c
    trunk/gcc/testsuite/gfortran.dg/reassoc_4.f
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/passes.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-2.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-6.c
    trunk/gcc/testsuite/gcc.dg/tree-ssa/recip-7.c
    trunk/gcc/tree-ssa-loop-niter.c
    trunk/gcc/tree-ssa-reassoc.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[rguenth at gcc dot gnu dot org]

------- Comment #10 from rguenth at gcc dot gnu dot org  2008-04-29 16:03 -------
The fold missed optimizations are fixed.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[rguenth at gcc dot gnu dot org]

------- Comment #9 from rguenth at gcc dot gnu dot org  2008-04-29 16:00 -------
Subject: Bug 15255

Author: rguenth
Date: Tue Apr 29 15:59:43 2008
New Revision: 134798

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=134798
Log:
2008-04-29  Richard Guenther  <rguenther@suse.de>

        PR middle-end/15255
        * fold-const.c (fold_binary): Fold (A + A) * C to A * 2*C.

        * gcc.dg/fold-plusmult.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/fold-plusmult.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/fold-const.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2008-04-29 14:17 -------
We already handle most of the foldings in fold_plusminus_mult_expr, just the
A + A -> 2 * A folding is not done (for a reason).

We also miss (A + A) * Cst -> A * 2 * Cst, which is what I am going to
implement
in addition to extending the tree re-association pass. 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255

[Bug tree-optimization/15255] [tree-ssa] a * 2 + a * 2 is not converted to a * 4

[rguenth at gcc dot gnu dot org]

------- Comment #7 from rguenth at gcc dot gnu dot org  2008-04-28 20:19 -------
Mine.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rguenth at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2006-02-20 18:43:31         |2008-04-28 20:19:51
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15255