[Bug optimization/14287] New: [tree-ssa] does not remove unnecessary extensions

[Bug optimization/14287] New: [tree-ssa] does not remove unnecessary extensions

[kazu at cs dot umass dot edu]

/* test.c */

short g, h;

void
foo (long a)
{
  short b = a & 3;
  long c = b;
  g = c;
  h = c;
}

test.c.t20.dom1 looks like so:

foo (a)
{
  long int c;
  short int b;
  short int T.1;
  short int T.0;

<bb 0>:
  T.0_2 = (short int)a_1;
  b_3 = T.0_2 & 3;
  c_4 = (long int)b_3;
  T.1_5 = (short int)c_4; <- Hey, T.1_5 == b_3!
  g = T.1_5;
  T.1_6 = T.1_5;
  h = T.1_5;
  return;
}

Here is the asm:

foo:
	movl	4(%esp), %eax
	andl	$3, %eax
	cwtl                   <- ugly
	movw	%ax, g
	movw	%ax, h
	ret

I inserted "g" and "h" to kill the combiner as it performs badly
when there are multiple uses of variables. :-)
The exactly same problem appears on H8.

-- 
           Summary: [tree-ssa] does not remove unnecessary extensions
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          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
GCC target triplet: i686-pc-linux-gnu, h8300-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-02-25 04:55 -------
Confirmed, this is a performance regression from the mainline.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|enhancement                 |normal
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |pessimizes-code
   Last reconfirmed|0000-00-00 00:00:00         |2004-02-25 04:55:03
               date|                            |
   Target Milestone|---                         |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-02-25 05:18 -------
No this is not a regression, I was looking at the asm wrong as the compiler that Kazu used was an i386 
compiler while mine is for i686.  This happens on the mainline too.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[amacleod at redhat dot com]

------- Additional Comments From amacleod at redhat dot com  2004-02-25 18:51 -------
huh, how did that happen, this went to the wrong bugzilla case. 
Sorry.... this patch is not for this case . I didnt even have this one open
anywhere. huh.

Andrew



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2004-03-03 18:13 -------
Mine.


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |kazu at cs dot umass dot edu
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[kazu at cs dot umass dot edu]

------- Additional Comments From kazu at cs dot umass dot edu  2004-03-04 04:08 -------
I'm not sure if I can quickly implement remove sign/zero extensions elimination
in a (almost always) profitable way.

It's more involved than I thought. :-(


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|kazu at cs dot umass dot edu|unassigned at gcc dot gnu
                   |                            |dot org
             Status|ASSIGNED                    |NEW


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-03-16 21:50 -------
Mine.

-- 
           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=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-03-17 01:46 -------
Actually it is not that involved at all.
Basically here is how my pass works:
For each block:
  For each statement in the block:
    is the statement is a modify expression and the RHS is a cast then:
      is the cast's operand's definition a modifiy express and its RHS a cast also:
        Do the inner and outer types match and is the intermediate's type size is larger or 
equal to the outer's type then remove change the statement to point to the outer variable.

Let DCE do its work with respect to getting rid of the intermediate variable.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-04-03 05:06 -------
Patch here: <http://gcc.gnu.org/ml/gcc-patches/2004-04/msg00169.html>, I forgot to 
mention this PR in the patch as this was the PR which got me thinking about casts in the 
first place.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug tree-optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-17 01:36 -------
Actually I found out that fold can do the same simplier and it also can be the done using 
the combine pass I am poposing in PR 15459.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |15459
           Keywords|patch                       |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug tree-optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287

[Bug tree-optimization/14287] [tree-ssa] does not remove unnecessary extensions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-06-21 05:07 -------
With the tree-combiner (which I am going to post soon), I get:

foo (a)
{
  short int T.1;

<bb 0>:
  T.1 = (short int)a & 3;
  g = T.1;
  h = T.1;
  return;

}

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14287