[Bug tree-optimization/21596] [4.0/4.1 Regression] extra temporaries when using global register variables

[Bug tree-optimization/21596] [4.0/4.1 Regression] extra temporaries when using global register variables

[pinskia at gcc dot gnu dot org]

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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor
   Last reconfirmed|2005-10-13 20:55:07         |2005-10-22 04:07:57
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1 Regression] extra temporaries when using global register variables

[mmitchel at gcc dot gnu dot org]

------- Comment #2 from mmitchel at gcc dot gnu dot org  2005-10-31 03:36 -------
Leaving this as P2.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2 Regression] extra temporaries when using global register variables

[mmitchel at gcc dot gnu dot org]

------- Comment #3 from mmitchel at gcc dot gnu dot org  2006-02-24 00:25 -------
This issue will not be resolved in GCC 4.1.0; retargeted at GCC 4.1.1.


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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.0.3                       |4.1.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2 Regression] extra temporaries when using global register variables

[mmitchel at gcc dot gnu dot org]

------- Comment #4 from mmitchel at gcc dot gnu dot org  2006-05-25 02:32 -------
Will not be fixed in 4.1.1; adjust target milestone to 4.1.2.


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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.1                       |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2 Regression] extra temporaries when using global register variables

[pinskia at gcc dot gnu dot org]

------- Comment #5 from pinskia at gcc dot gnu dot org  2006-07-05 09:27 -------
It is slightly different now:
        leal    -4(%edi), %eax
        movl    %eax, %edi
        movl    (%eax), %eax
        testl   %eax, %eax
But still the same issue.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2006-02-01 04:41:22         |2006-07-05 09:27:30
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2 Regression] extra temporaries when using global register variables

[steven at gcc dot gnu dot org]

------- Comment #6 from steven at gcc dot gnu dot org  2006-07-22 11:08 -------
In the greg dump we have this RTL:

(insn:HI 10 8 11 2 (parallel [
            (set (reg:SI 58 [ D.1540 ])
                (plus:SI (reg/v:SI 5 di [ reg ])
                    (const_int -4 [0xfffffffffffffffc])))
            (clobber (reg:CC 17 flags))
        ]) 208 {*addsi_1} (nil)
    (expr_list:REG_UNUSED (reg:CC 17 flags)
        (expr_list:REG_DEAD (reg/v:SI 5 di [ reg ])
            (expr_list:REG_UNUSED (reg:CC 17 flags)
                (nil)))))

(insn:HI 11 10 12 2 (set (reg/v:SI 5 di [ reg ])
        (reg:SI 58 [ D.1540 ])) 40 {*movsi_1} (insn_list:REG_DEP_TRUE 10 (nil))
    (nil))

(insn:HI 12 11 13 2 (set (reg:CCNO 17 flags)
        (compare:CCNO (mem:SI (reg:SI 58 [ D.1540 ]) [3 S4 A32])
            (const_int 0 [0x0]))) 3 {*cmpsi_ccno_1} (nil)
    (expr_list:REG_DEAD (reg:SI 58 [ D.1540 ])
        (nil)))

reg 5 and pseudoreg 58 can share the same hard register (i.e. 58 renumbers to
5) but GCC concludes that the two regs conflict.


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steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ra


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[mmitchel at gcc dot gnu dot org]

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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.2                       |4.1.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[amacleod at redhat dot com]

------- Comment #7 from amacleod at redhat dot com  2007-03-05 22:43 -------
Created an attachment (id=13149)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13149&action=view)
proposed patch for 4.3

This patch removes one of the temporary copies.  With this minor tuning of one
of TERs heuristics, the tree optimizers produce:
  reg.27 = reg - 4B;
  reg = reg.27;
  return *reg.27 <= 0;

Getting rid of the remaining middle copy is slightly little tricker, because it
involves a VDEF.

On mainline, this produces the (I think) desired assembly:
        subl    $4, %edi
        xorl    %eax, %eax
        cmpl    $0, -4(%edi)
        setle   %al
        ret


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[amacleod at redhat dot com]

------- Comment #8 from amacleod at redhat dot com  2007-03-05 22:52 -------
Created an attachment (id=13150)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=13150&action=view)
proposed patch for 4.2

This is the same patch for the 4.2 compiler.  Unfortunately, its not quite good
enough because the rtl optimizers still manage to do the wrong thing.  

In mainline, life recognizes that the register is dead in the copy:
(insn 7 5 8 2 (parallel [
            (set (reg:SI 58 [ reg.27 ])                 
               (plus:SI (reg/v:SI 5 di [ reg ])
                    (const_int -4 [0xfffffffc])))
            (clobber (reg:CC 17 flags))
        ]) 148 {*addsi_1} (nil)
    (expr_list:REG_DEAD (reg/v:SI 5 di [ reg ])
        (expr_list:REG_UNUSED (reg:CC 17 flags)             (nil))))

(insn 8 7 9 2 (set (reg/v:SI 5 di [ reg ])
        (reg:SI 58 [ reg.27 ])) 34 {*movsi_1} (insn_list:REG_DEP_TRUE 7 (nil))
    (expr_list:REG_DEAD (reg:SI 58 [ reg.27 ])
        (nil)))

and combine turns it into:

(insn 8 7 9 2 (parallel [
            (set (reg/v:SI 5 di [ reg ])
                (plus:SI (reg/v:SI 5 di [ reg ])
                    (const_int -4 [0xfffffffc])))
            (clobber (reg:CC 17 flags))
        ]) 148 {*addsi_1} (nil)


on the 4.2 branch, we don't seem to get it right and combine, nor anyone else I
suppose, manages to get merge the 2 insns.   so we end up aith the same
assembly. 

Unless someone sees something in the RTL optimizers that can be tweaked that
can figure this out, there isn't much point in applying this to 4.2.

Im not planning to look into the RTL side myself, but I will see if there is
anything else TER can do to get rid of this situation in 4.2.




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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[amacleod at redhat dot com]

------- Comment #9 from amacleod at redhat dot com  2007-03-06 15:01 -------
actually, mainline isn't working either.  A closer examination shows the code
generated has an extra offset of -4 in the compare that shouldn't be there.
This patch triggers a bug in rtl's fwprop pass. 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[bonzini at gnu dot org]

------- Comment #10 from bonzini at gnu dot org  2007-03-07 08:22 -------
Unfortunately, if I fix the fwprop bug (which is actually caused by wrong df
information), I get again

        leal    -4(%edi), %eax
        movl    %eax, %edi
        movl    (%eax), %eax
        testl   %eax, %eax

The df bug is fixed by:

Index: ../../base-gcc-src/gcc/df-scan.c
===================================================================
--- ../../base-gcc-src/gcc/df-scan.c    (revision 122624)
+++ ../../base-gcc-src/gcc/df-scan.c    (working copy)
@@ -1833,6 +1833,13 @@ df_record_entry_block_defs (struct dataf
 #endif
     }

+  /* Mark all global registers as being defined at the entry of the
+     function since values set by our caller should not be treated as
+     uninitialized.  */
+  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    if (global_regs[i])
+      bitmap_set_bit (df->entry_block_defs, i);
+  
   /* Once the prologue has been generated, all of these registers
      should just show up in the first regular block.  */
   if (HAVE_prologue && epilogue_completed)


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bonzini at gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bonzini at gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[mmitchel at gcc dot gnu dot org]

------- Comment #11 from mmitchel at gcc dot gnu dot org  2007-03-10 01:39 -------
In this message:

http://gcc.gnu.org/ml/gcc/2007-03/msg00249.html

Andre Macleod indicates that this will be difficult to fix in pre-4.3
compilers.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2007-08-23 16:14 -------
So, on the mainline we now generate wrong-code?!


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[steven at gcc dot gnu dot org]

------- Comment #13 from steven at gcc dot gnu dot org  2007-11-19 08:56 -------
Maybe a wrong-code bug and it is "minor" and P2?  Someone please update the
status of this report :-)


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steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2/4.3 Regression] extra temporaries when using global register variables

[pinskia at gcc dot gnu dot org]

------- Comment #14 from pinskia at gcc dot gnu dot org  2007-11-19 09:08 -------
This still fails on the mainline.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
           Keywords|wrong-code                  |
   Last reconfirmed|2007-08-06 14:58:23         |2007-11-19 09:08:47
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.0/4.1/4.2 Regression] extra temporaries when using global register variables

[pinskia at gcc dot gnu dot org]

------- Comment #15 from pinskia at gcc dot gnu dot org  2007-11-19 09:35 -------
Actually we get:
        subl    $4, %edi
        subl    $12, %esp
        xorl    %eax, %eax
        cmpl    $0, -4(%edi)
        setle   %al
        addl    $12, %esp

So this is fixed for the trunk.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.0/4.1/4.2/4.3 Regression]|[4.0/4.1/4.2 Regression]
                   |extra temporaries when using|extra temporaries when using
                   |global register variables   |global register variables


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.2 Regression] extra temporaries when using global register variables

[jsm28 at gcc dot gnu dot org]

------- Comment #16 from jsm28 at gcc dot gnu dot org  2008-07-04 16:53 -------
Closing 4.1 branch.


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jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.1/4.2 Regression] extra  |[4.2 Regression] extra
                   |temporaries when using      |temporaries when using
                   |global register variables   |global register variables
   Target Milestone|4.1.3                       |4.2.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596

[Bug tree-optimization/21596] [4.2 Regression] extra temporaries when using global register variables

[jsm28 at gcc dot gnu dot org]

------- Comment #17 from jsm28 at gcc dot gnu dot org  2009-03-30 15:44 -------
Closing 4.2 branch, fixed in 4.3.


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jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
      Known to fail|4.0.4                       |4.0.4 4.2.5
      Known to work|                            |4.3.0
         Resolution|                            |FIXED
   Target Milestone|4.2.5                       |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21596