[Bug tree-optimization/24427] New: missing optimization opportunity with binary operators

[Bug tree-optimization/24427] New: missing optimization opportunity with binary operators

[dvilleneuve at kronos dot com]

In the code below, the test is always true and could be found as such by using
distributivity on binary operators to factor out constant values.  This is not
currently done, by looking at the assembly code produced.

<code>
extern int f(unsigned);

int f(unsigned u)
{
  if( (u|4) & 6 ) /* could be tested as (u&6) || (4&6), always true */
    return 5;
  else
    return 10;
}
</code>


-- 
           Summary: missing optimization opportunity with binary operators
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P4
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dvilleneuve at kronos dot com
GCC target triplet: i386-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2005-10-18 13:42 -------
Confirmed.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |19987
              nThis|                            |
             Status|UNCONFIRMED                 |NEW
          Component|tree-optimization           |middle-end
     Ever Confirmed|0                           |1
           Keywords|                            |missed-optimization
   Last reconfirmed|0000-00-00 00:00:00         |2005-10-18 13:42:23
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2005-10-19 10:25 -------
fold-const.c:distribute_bit_expr should be extended to handle this case.


-- 

rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[sayle at gcc dot gnu dot org]

------- Comment #3 from sayle at gcc dot gnu dot org  2006-02-13 18:33 -------
Subject: Bug 24427

Author: sayle
Date: Mon Feb 13 18:33:32 2006
New Revision: 110918

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=110918
Log:

        PR middle-end/24427
        * fold-const.c (fold_binary) <BIT_IOR_EXPR>: Transform (X&C1)|C2
        into (X,C2) if C1 is a subset of the bits of C2.  Transform
        (X&C1)|C2 into X|C2 if C1|C2 == ~0.  Canonicalize (X&C1)|C2 as
        (X&(C1&~C2))|C2.
        <BIT_AND_EXPR>: Canonicalize (X|C1)&C2 as (X&C2)|(C1&C2).

        * gcc.dg/tree-ssa/andor-1.c: New test case.


Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/andor-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/fold-const.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[roger at eyesopen dot com]

------- Comment #4 from roger at eyesopen dot com  2006-02-14 03:07 -------
This has now been fixed on mainline.


-- 

roger at eyesopen dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[ramana dot radhakrishnan at codito dot com]

------- Comment #5 from ramana dot radhakrishnan at codito dot com  2006-06-26 19:13 -------
This should be reopened. A related testcase shows a regression from 3.4.6 to
4.1.1 for m68k-elf shows a regression . combine used to take care of this in
3.4.6   . A backport of the patch is ready with me. If its allowed, I'll put it
up . 

This is the test case . 

#include <stdio.h>
int i;
int main (void)
{

          if ( ((i & ~1) | 1) != ( i | 1))
                      printf ("abc");
}

3.4.6 generated 

       .file   "fail.c"
        .text
        .align  2
        .globl  foo
        .type   foo, @function
foo:
        link.w %a6,#0
        unlk %a6
        rts
        .size   foo, .-foo
        .comm   i,4,2
        .ident  "GCC: (GNU) 3.4.6"



4.1.2 pre-release generates      

.file   "fail.c"
        .section        .rodata.str1.1,"aMS",@progbits,1
.LC0:
        .string "abc"
        .text
        .align  2
        .globl  main
        .type   main, @function
main:
        link.w %fp,#0
        move.l %d2,-(%sp)
        move.l i,%d1
        moveq #-2,%d0
        and.l %d1,%d0
        moveq #1,%d2
        or.l %d2,%d0
        or.l %d2,%d1
        cmp.l %d0,%d1
        jbeq .L5
        pea .LC0
        jbsr printf
        addq.l #4,%sp
.L5:
        move.l -4(%fp),%d2
        unlk %fp
        rts
        .size   main, .-main
        .comm   i,4,2
        .ident  "GCC: (GNU) 4.1.2 20060623 (prerelease)"


-- 

ramana dot radhakrishnan at codito dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ramana dot radhakrishnan at
                   |                            |codito dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[bangerth at dealii dot org]

------- Comment #6 from bangerth at dealii dot org  2006-09-13 04:02 -------
Isn't this a duplicate of PR 28173 now?


-- 

bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at dealii dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[pinskia at gcc dot gnu dot org]

------- Comment #7 from pinskia at gcc dot gnu dot org  2006-09-13 04:08 -------
(In reply to comment #6)
> Isn't this a duplicate of PR 28173 now?
Besides PR 28173 is a regression.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[sayle at gcc dot gnu dot org]

------- Comment #8 from sayle at gcc dot gnu dot org  2007-02-18 17:10 -------
Subject: Bug 24427

Author: sayle
Date: Sun Feb 18 17:10:19 2007
New Revision: 122100

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=122100
Log:

        Backport from mainline.
        PR middle-end/24427
        PR rtl-optimization/28173
        * fold-const.c (fold_binary) <BIT_IOR_EXPR>: Transform (X&C1)|C2
        into (X,C2) if C1 is a subset of the bits of C2.  Transform
        (X&C1)|C2 into X|C2 if C1|C2 == ~0.  Canonicalize (X&C1)|C2 as
        (X&(C1&~C2))|C2.
        <BIT_AND_EXPR>: Canonicalize (X|C1)&C2 as (X&C2)|(C1&C2).

        * gcc.dg/tree-ssa/andor-1.c: New test case.


Added:
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tree-ssa/andor-1.c
Modified:
    branches/gcc-4_1-branch/gcc/ChangeLog
    branches/gcc-4_1-branch/gcc/fold-const.c
    branches/gcc-4_1-branch/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[ebotcazou at gcc dot gnu dot org]

------- Comment #9 from ebotcazou at gcc dot gnu dot org  2007-02-18 17:58 -------
Roger, I'm a little puzzled by your last move: is it really necessary to
backport a patch for a missed optimization, after a delay of 1 full year,
to a branch which is supposed to be in stabilization mode now?  IMHO it's
too late.


-- 

ebotcazou at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sayle at gcc dot gnu dot
                   |                            |org, ebotcazou at gcc dot
                   |                            |gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[roger at eyesopen dot com]

------- Comment #10 from roger at eyesopen dot com  2007-02-18 18:10 -------
Hi Eric,

It's not PR24427 that's the motivation for this backport, but PR 28173.
In fact, it was *your* request in comment #2 of PR28173 to backport this!
I'm a little disappointed you'd even question my decision/authority to
backport a regression fix. :-)

Roger
--


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427

[Bug middle-end/24427] missing optimization opportunity with binary operators

[ebotcazou at gcc dot gnu dot org]

------- Comment #11 from ebotcazou at gcc dot gnu dot org  2007-02-18 18:50 -------
> It's not PR24427 that's the motivation for this backport, but PR 28173.
> In fact, it was *your* request in comment #2 of PR28173 to backport this!

Well, I only requested that you comment on the proposed backport.  And this
was on 2006-09-13, so 5 months ago!

> I'm a little disappointed you'd even question my decision/authority to
> backport a regression fix. :-)

I'm basically paid for that. :-)


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24427