[Bug c/16356] New: Failure to use count register

[Bug c/16356] New: Failure to use count register

[anton at samba dot org]

I was retesting bug 14886 on 3.5 cvs (20040703) and noticed the count register
is not being used in 64bit:

float bar;

void f1 (void)
{
  int i;
  for (i = 0; i < 500; i++)
    __asm__ __volatile__ ("# %0" : : "f" (i * bar));
}

gives:

.L2:
        rldicl. 0,11,0,53
        sradi 9,11,53
        addi 9,9,1
        cmpldi 7,9,2
        beq- 0,.L3
        xor 0,11,0
        blt- 7,.L3
        ori 11,0,2048
.L3:
        lfs 13,0(10)
        std 11,-16(1)
        lfd 12,-16(1)
        fcfid 12,12
        frsp 0,12
        fmuls 0,0,13
#APP
        # 0
#NO_APP
        addi 0,11,1
        extsw 11,0
        cmpwi 7,11,499
        ble+ 7,.L2

-- 
           Summary: Failure to use count register
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: anton at samba dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-07-04 07:07 -------
This might be a regression though, because the doloop optimization was rewritten for 3.5.0.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
          Component|c                           |rtl-optimization
           Keywords|                            |missed-optimization
            Summary|Failure to use count        |Failure to use count
                   |register                    |register (branch on count
                   |                            |register)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-07-04 19:42 -------
Confirmed, not a regression.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
      Known to fail|                            |3.4.0 3.5.0
   Last reconfirmed|0000-00-00 00:00:00         |2004-07-04 19:42:09
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[rakdver at gcc dot gnu dot org]

------- Additional Comments From rakdver at gcc dot gnu dot org  2004-07-06 01:23 -------
What happens is that some pretty weird stuff is done with the counter of the 
loop (reg 119) before it is incremented (later in bb 4), see below.  I don't
quite understand what is the code is supposed to do.

The register 119 then of course is not recognized as an induction variable,
and doloop optimization cannot happen.

Zdenek

(insn 17 15 18 1 (parallel [
            (set (reg:CC 123)
                (compare:CC (and:DI (reg/v:DI 119 [ i ])
                        (const_int 2047 [0x7ff]))
                    (const_int 0 [0x0])))
            (set (reg:DI 121)
                (and:DI (reg/v:DI 119 [ i ])
                    (const_int 2047 [0x7ff])))
            (clobber (scratch:CC))
        ]) -1 (nil)
    (nil))

(insn 18 17 19 1 (set (reg:DI 122)
        (ashiftrt:DI (reg/v:DI 119 [ i ])
            (const_int 53 [0x35]))) -1 (nil)
    (nil))

(insn 19 18 20 1 (set (reg:DI 122)
        (plus:DI (reg:DI 122)
            (const_int 1 [0x1]))) -1 (nil)
    (nil))

(jump_insn 20 19 43 1 (set (pc)
        (if_then_else (eq (reg:CC 123)
                (const_int 0 [0x0]))
            (label_ref 25)
            (pc))) -1 (nil)
    (expr_list:REG_BR_PROB (const_int 5000 [0x1388])
        (nil)))
;; End of basic block 1, registers live:
 (nil)

;; Start of basic block 2, registers live: (nil)
(note 43 20 21 2 [bb 2] NOTE_INSN_BASIC_BLOCK)

(insn 21 43 22 2 (set (reg:CCUNS 124)
        (compare:CCUNS (reg:DI 122)
            (const_int 2 [0x2]))) -1 (nil)
    (nil))

(jump_insn 22 21 44 2 (set (pc)
        (if_then_else (ltu (reg:CCUNS 124)
                (const_int 0 [0x0]))
            (label_ref 25)
            (pc))) -1 (nil)
    (expr_list:REG_BR_PROB (const_int 5000 [0x1388])
        (nil)))
;; End of basic block 2, registers live:
 (nil)

;; Start of basic block 3, registers live: (nil)
(note 44 22 23 3 [bb 3] NOTE_INSN_BASIC_BLOCK)

(insn 23 44 24 3 (set (reg/v:DI 119 [ i ])
        (xor:DI (reg/v:DI 119 [ i ])
            (reg:DI 121))) -1 (nil)
    (nil))

(insn 24 23 25 3 (set (reg/v:DI 119 [ i ])
        (ior:DI (reg/v:DI 119 [ i ])
            (const_int 2048 [0x800]))) -1 (nil)
    (nil))
;; End of basic block 3, registers live:
 (nil)

;; Start of basic block 4, registers live: (nil)
(code_label 25 24 45 4 3 "" [2 uses])

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[amodra at bigpond dot net dot au]

------- Additional Comments From amodra at bigpond dot net dot au  2004-11-25 14:08 -------
The "weird stuff" is floatdisf2_internal2.  It should be using a new output
register instead of changing its input.  Fixing.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |amodra at bigpond dot net
                   |dot org                     |dot au
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-11-26 04:38 -------
Subject: Bug 16356

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	amodra@gcc.gnu.org	2004-11-26 04:38:13

Modified files:
	gcc            : ChangeLog 
	gcc/config/rs6000: rs6000.md 

Log message:
	PR rtl-optimization/16356
	* config/rs6000/rs6000.md (floatdisf2_internal2): Rewrite with
	separate output register and one less jump.  Enable for powerpc64.
	(floatdisf2): Adjust for above.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&r1=2.6564&r2=2.6565
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/rs6000/rs6000.md.diff?cvsroot=gcc&r1=1.334&r2=1.335



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-11-26 04:39 -------
Subject: Bug 16356

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	amodra@gcc.gnu.org	2004-11-26 04:38:53

Modified files:
	gcc            : ChangeLog 
	gcc/config/rs6000: rs6000.md 

Log message:
	PR rtl-optimization/16356
	* config/rs6000/rs6000.md (floatdisf2_internal2): Rewrite with
	separate output register and one less jump.  Enable for powerpc64.
	(floatdisf2): Adjust for above.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.703&r2=2.2326.2.704
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/rs6000/rs6000.md.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.284.4.13&r2=1.284.4.14



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[amodra at bigpond dot net dot au]

------- Additional Comments From amodra at bigpond dot net dot au  2004-11-26 04:46 -------
Fixed mainline and gcc-3.4 branch

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356

[Bug rtl-optimization/16356] Failure to use count register (branch on count register)

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16356