[Bug rtl-optimization/17169] optimization bug

[Bug rtl-optimization/17169] optimization bug

[ebotcazou at gcc dot gnu dot org]

------- Comment #3 from ebotcazou at gcc dot gnu dot org  2007-05-17 15:17 -------
3.4.x is not maintained anymore.


-- 

ebotcazou at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot gnu dot
                   |                            |org
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17169

[Bug rtl-optimization/17169] optimization bug

[sje at cup dot hp dot com]

------- Additional Comments From sje at cup dot hp dot com  2005-01-10 23:43 -------
I looked into this bug some, it is fixed on 4.0, but the patch that fixes it is
the integration of tree-ssa into the mainline.  I believe that the underlying
combine bug still exists but the tree-ssa changes result in different RTL being
generated so that the combine bug isn't hit.  I looked at try_combine using the
3.4 sources.  Attached is  the i1, i2, i3 values we enter try_combine with and
what it generates.  I have no idea how it came up with the result that it did
but that seems to be the heart of the problem.


In try_combine:

I1 is
(nil)
I2 is
(insn 53 51 54 2 (set (reg:BI 360)
        (eq:BI (reg/v:SI 341 [ rnd_mode ])
            (const_int 2 [0x2]))) 209 {*cmpsi_normal} (nil)
    (expr_list:REG_DEAD (reg/v:SI 341 [ rnd_mode ])
        (nil)))
I3 is
(insn 57 56 58 2 (set (reg:BI 363)
        (and:BI (gt:BI (reg/v:SI 342 [ signx ])
                (const_int 0 [0x0]))
            (reg:BI 360))) 66 {*cmpsi_and_1} (insn_list 53 (nil))
    (expr_list:REG_DEAD (reg/v:SI 342 [ signx ])
        (expr_list:REG_DEAD (reg:BI 360)
            (nil))))
==========================
Returns:

(insn 57 56 58 2 (set (reg:BI 363)
        (const_int 0 [0x0])) 1 {movbi} (nil)
    (nil))
==========================

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sje at cup dot hp dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17169

[Bug rtl-optimization/17169] optimization bug

[wilson at gcc dot gnu dot org]

------- Additional Comments From wilson at gcc dot gnu dot org  2004-08-26 02:03 -------
Appears to be a problem in combine.  We have 3 possible return values before
combine, but only two possible return values after combine.  I haven't traced
through combine far enough yet to determine what the problem is.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-08-26 02:03:30
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17169

[Bug rtl-optimization/17169] optimization bug

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |rtl-optimization
           Keywords|                            |wrong-code
      Known to work|                            |3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17169