[Bug optimization/3511] Inlined strlen() could be smarter

[Bug optimization/3511] Inlined strlen() could be smarter

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-16 22:53 -------
This is a O(n_bbs^3 * variables) problem but I would say it is douable.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug optimization/3511] Inlined strlen() could be smarter

[pinskia at gcc dot gnu dot org]

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug optimization/3511] Inlined strlen() could be smarter

[pinskia at gcc dot gnu dot org]

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           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug optimization/3511] Inlined strlen() could be smarter

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-03-08 05:40 -------
This shows up in SPEC 2000's 176.gcc, also it might be easier on the tree-ssa:
;; Function mystrlen (mystrlen)

mystrlen (s)
{
  long unsigned int T.0;

<bb 0>:
  if (s_2 == 0B) goto <L0>; else goto <L1>;

<L0>:;

  # s_1 = PHI <s_2(0), ""(1)>;
<L1>:;
  T.0_3 = strlen (s_1);
  return T.0_3;

}

Moving the constant back to the other basic block and splitting thrid basic block and have 
the second basic block goto the last and the first on the false edge goto the new one with 
the call to strlen.

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           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
             Status|SUSPENDED                   |NEW
   Last reconfirmed|2003-11-05 07:41:23         |2004-03-08 05:41:08
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug tree-optimization/3511] Inlined strlen() could be smarter

[pinskia at gcc dot gnu dot org]

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug tree-optimization/3511] Inlined strlen() could be smarter

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2005-01-23 15:01 -------
GCC produces the following code today: 
 
        .section        .rodata.str1.1,"aMS",@progbits,1 
.LC0: 
        .string "" 
        .text 
        .p2align 4,,15 
.globl mystrlen 
        .type   mystrlen, @function 
mystrlen: 
        pushl   %ebp 
        movl    %esp, %ebp 
        movl    8(%ebp), %eax 
        testl   %eax, %eax 
        je      .L6 
        movl    %eax, 8(%ebp) 
        leave 
        jmp     strlen 
        .p2align 4,,7 
.L6: 
        movl    $.LC0, %eax 
        movl    %eax, 8(%ebp) 
        leave 
        jmp     strlen 
        .size   mystrlen, .-mystrlen 
        .ident  "GCC: (GNU) 4.0.0 20050123 (experimental)" 
 

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           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2004-12-13 02:55:40         |2005-01-23 15:01:49
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug tree-optimization/3511] Inlined strlen() could be smarter

[rguenth at gcc dot gnu dot org]

------- Comment #9 from rguenth at gcc dot gnu dot org  2006-10-21 13:23 -------
Fixed.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug tree-optimization/3511] Inlined strlen() could be smarter

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2006-10-21 13:23 -------
Subject: Bug 3511

Author: rguenth
Date: Sat Oct 21 13:23:41 2006
New Revision: 117932

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117932
Log:
2006-10-21  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/3511
        * tree-ssa-pre.c (phi_translate): Fold CALL_EXPRs that
        got new invariant arguments during PHI translation.

        * gcc.dg/tree-ssa/ssa-pre-15.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-15.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-pre.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug tree-optimization/3511] Inlined strlen() could be smarter

[patchapp at dberlin dot org]

------- Comment #7 from patchapp at dberlin dot org  2006-05-15 19:22 -------
Subject: Bug number PR3511

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2006-05/msg00295.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug tree-optimization/3511] Inlined strlen() could be smarter

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2006-05-08 12:39 -------
It looks like it was easy.  (so, I have a patch)


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rguenth at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2005-12-07 03:04:59         |2006-05-08 12:39:11
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511

[Bug tree-optimization/3511] Inlined strlen() could be smarter

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2006-05-08 09:42 -------
This is really a PRE problem, much like the simplified testcase

char firstchar (const char *s)
{
        if (!s)
                s = "";
        return s[0];
}

where it could record the fact that the load from s[0] is available as
is strlen(s).  Now, if it is worth it is another question.

Danny, will the new VN do anything about this, or make it easier to tackle
this problem?  Now, ccp has moved the assignment into a PHI node, which may
make this more complicated (this is after PRE):

mystrlen (s)
{
  size_t D.1648;

<bb 2>:
  if (s_2 == 0B) goto <L4>; else goto <L3>;

<L4>:;
  goto <bb 4> (<L1>);

<L3>:;

  # s_1 = PHI <s_2(3), &""[0](5)>;
<L1>:;
  #   VUSE <SMT.4_6>;
  D.1648_3 = strlen (s_1);
  return D.1648_3;

}


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rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3511