[Bug tree-optimization/26258] New: [4.1 Regression] Wrong alias information for SRAed struct copy

[Bug tree-optimization/26258] New: [4.1 Regression] Wrong alias information for SRAed struct copy

[rguenth at gcc dot gnu dot org]

Compiling with -O2 the following creates invalid virtual operands after
SRA:

struct Foo { int a; int b; };

Foo foo(Foo p, bool ret_first)
{
  Foo first = p;
  Foo last = p;
  return ret_first ? first : last;
}

  # iftmp.0D.1761_1 = PHI <&firstD.1740(1), &lastD.1757(0)>;
<L2>:;
  #   VUSE <SFT.6D.1783_24>;
  #   VUSE <SFT.8D.1785_26>;
  SR.26D.1803_27 = iftmp.0D.1761_1->bD.1735;
  #   VUSE <SFT.6D.1783_24>;
  #   VUSE <SFT.8D.1785_26>;
  SR.25D.1802_28 = iftmp.0D.1761_1->aD.1734;

the access to ->b should VUSE SFTs 5 and 7.


-- 
           Summary: [4.1 Regression] Wrong alias information for SRAed
                    struct copy
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: wrong-code, alias
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1 Regression] Wrong alias information for SRAed struct copy

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2006-02-13 15:24 -------
C testcase works correctly.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|4.1.0                       |
      Known to work|4.2.0 4.0.3                 |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1 Regression] Wrong alias information for SRAed struct copy

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2006-02-13 15:31 -------
C testcase that fails (the PHI <&first, &last> is the important part):

typedef struct { int a; int b; } Foo;

Foo foo(Foo p, _Bool ret_first)
{
  Foo first = p;
  Foo last = p;
  Foo *q;
  q = ret_first ? &first : &last;
  return *q;
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1 Regression] Wrong alias information for struct

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2006-02-13 15:32 -------
You can invoke the wrong aliasing before SRA:
typedef struct Foo { int a; int b; }Foo;

Foo foo(Foo first, Foo last, bool ret_first)
{
  Foo t;
  Foo *t1 = (ret_first ? &first : &last);
  t.a = t1->a;
  t.b = t1->b;
  return t;
}


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.1 Regression] Wrong alias|[4.1 Regression] Wrong alias
                   |information for SRAed struct|information for struct
                   |copy                        |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2006-02-13 15:37 -------
Testcase for the mainline:
typedef struct Foo { int a; int b; }Foo;

Foo foo(Foo first, Foo last, bool ret_first)
{
  Foo t;
  Foo *t1 = (ret_first ? &first : &last);
  first.a = 2;
  last.b = 3;
  t.a = t1->a;
  t.b = t1->b;
  t.a += first.a;
  t.b += last.b;
  return t;
}


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-02-13 15:37:29
               date|                            |
            Summary|[4.1 Regression] Wrong alias|[4.1/4.2 Regression] Wrong
                   |information for struct      |alias information for struct


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct

[pinskia at gcc dot gnu dot org]

------- Comment #5 from pinskia at gcc dot gnu dot org  2006-02-13 15:42 -------
For the testcase in comment #4:
Points-to analysis

Constraints:
t1_1 = &first
t1_1 = &last

Solving graph:

Points-to sets
t1_1 = { first last }

Pointed-to sets for pointers in foo

t1_1, name memory tag: NMT.17, is dereferenced, points-to vars: { SFT.4 SFT.6 }


----

t1_1 is wrong in "Pointed-to sets for pointers in foo".  maybe we forget to add
all the SFT's or something.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct

[pinskia at gcc dot gnu dot org]

------- Comment #6 from pinskia at gcc dot gnu dot org  2006-02-13 15:44 -------
Actually contstraints is wrong.
in the first aliasing pass before proping into the addresses into PHI's:
iftmp.0_25 = &first
iftmp.0_25 = &first.b
iftmp.0_24 = &last
iftmp.0_24 = &last.b


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct addresses in PHIs

[rguenth at gcc dot gnu dot org]

------- Comment #7 from rguenth at gcc dot gnu dot org  2006-02-13 16:25 -------
I have a patch.


-- 

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|2006-02-13 15:37:29         |2006-02-13 16:25:48
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct addresses in PHIs

[mmitchel at gcc dot gnu dot org]

------- Comment #8 from mmitchel at gcc dot gnu dot org  2006-02-14 09:08 -------
Sadly, this is a P1; a nasty optimization bug, on code without extensions,
probably architecture independent, and did not exist in previous releases.


-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|rguenth at gcc dot gnu dot  |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|ASSIGNED                    |NEW
           Priority|P3                          |P1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct addresses in PHIs

[rguenth at gcc dot gnu dot org]

------- Comment #9 from rguenth at gcc dot gnu dot org  2006-02-14 09:54 -------
Subject: Bug 26258

Author: rguenth
Date: Tue Feb 14 09:54:07 2006
New Revision: 110962

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=110962
Log:
2006-02-14  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/26258
        * tree-ssa-structalias.c (find_func_aliases): Handle aggregates
        in PHI argument processing.

        * gcc.dg/torture/pr26258.c: New testcase.

Added:
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/torture/pr26258.c
Modified:
    branches/gcc-4_1-branch/gcc/ChangeLog
    branches/gcc-4_1-branch/gcc/testsuite/ChangeLog
    branches/gcc-4_1-branch/gcc/tree-ssa-structalias.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct addresses in PHIs

[rguenth at gcc dot gnu dot org]

------- Comment #10 from rguenth at gcc dot gnu dot org  2006-02-14 09:59 -------
Subject: Bug 26258

Author: rguenth
Date: Tue Feb 14 09:58:57 2006
New Revision: 110963

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=110963
Log:
2006-02-14  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/26258
        * tree-ssa-structalias.c (find_func_aliases): Handle aggregates
        in PHI argument processing.

        * gcc.dg/torture/pr26258.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.dg/torture/pr26258.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-structalias.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258

[Bug tree-optimization/26258] [4.1/4.2 Regression] Wrong alias information for struct addresses in PHIs

[rguenth at gcc dot gnu dot org]

------- Comment #11 from rguenth at gcc dot gnu dot org  2006-02-14 09:59 -------
Fixed.


-- 

rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26258