[Bug c/43438] New: possible wrong code bug

[Bug c/43438] New: possible wrong code bug

[regehr at cs dot utah dot edu]

The -O0 result looks right.  This behavior observed on x86 using r157445 and
x64 using r157542.

regehr@john-home:~$ current-gcc -O0 small.c -o small -Wall 
regehr@john-home:~$ ./small
1
regehr@john-home:~$ current-gcc -O1 small.c -o small -Wall 
regehr@john-home:~$ ./small
0
regehr@john-home:~$ cat small.c
extern int printf (__const char *__restrict __format, ...);

static unsigned char g_2 = 1;
static int g_9;
static int *l_8 = &g_9;

static void func_12(int p_13)
{
  int * l_17 = &g_9;
  *l_17 &= 0 < p_13;
}

int main(void)
{
  unsigned char l_11 = 254;
  *l_8 |= g_2;
  l_11 |= *l_8;
  func_12(l_11);
  printf("%d\n", g_9);
  return 0;
} 
regehr@john-home:~$ current-gcc -v
Using built-in specs.
COLLECT_GCC=current-gcc
COLLECT_LTO_WRAPPER=/home/regehr/z/compiler-install/gcc-r157445-install/libexec/gcc/i686-pc-linux-gnu/4.5.0/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: ../configure --with-libelf=/usr/local --enable-lto
--prefix=/home/regehr/z/compiler-install/gcc-r157445-install
--program-prefix=r157445- --enable-languages=c,c++
Thread model: posix
gcc version 4.5.0 20100314 (experimental) (GCC)


-- 
           Summary: possible wrong code bug
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: regehr at cs dot utah dot edu
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug c/43438] possible wrong code bug

[sezeroz at gmail dot com]

------- Comment #1 from sezeroz at gmail dot com  2010-03-19 06:51 -------
Happened on x86_64-pc-linux and my gcc-4.4 was affected too, gcc-3.4.6 seemed
fine.


-- 

sezeroz at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sezeroz at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug c/43438] possible wrong code bug

[mikpe at it dot uu dot se]

------- Comment #2 from mikpe at it dot uu dot se  2010-03-19 09:46 -------
4.2.4/4.3.4/4.4.3 are affected, 4.1.2 and older seem to be Ok.


-- 

mikpe at it dot uu dot se changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpe at it dot uu dot se


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug c/43438] [4.3/4.4/4.5 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2010-03-19 11:02 -------
Confirmed.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
  GCC build triplet|i686-pc-linux-gnu           |
   GCC host triplet|i686-pc-linux-gnu           |
 GCC target triplet|i686-pc-linux-gnu           |i?86-*-* x86_64-*-*
           Keywords|                            |wrong-code
      Known to fail|                            |4.3.4 4.4.3 4.5.0
      Known to work|                            |4.1.2
   Last reconfirmed|0000-00-00 00:00:00         |2010-03-19 11:02:13
               date|                            |
            Summary|possible wrong code bug     |[4.3/4.4/4.5 Regression]
                   |                            |possible wrong code bug
   Target Milestone|---                         |4.3.5
            Version|unknown                     |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3/4.4/4.5 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2010-03-19 11:29 -------
Combine breaks this.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |rtl-optimization


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3/4.4/4.5 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2010-03-19 11:35 -------
It combines

(insn 6 5 7 2 t.c:16 (parallel [
            (set (reg:SI 59 [ D.2732 ])
                (ior:SI (reg:SI 67 [ g_9 ])
                    (const_int 1 [0x1])))
            (clobber (reg:CC 17 flags))
        ]) 394 {*iorsi_1} (expr_list:REG_DEAD (reg:SI 67 [ g_9 ])
        (expr_list:REG_UNUSED (reg:CC 17 flags)
            (expr_list:REG_EQUAL (ior:SI (mem/c/i:SI (symbol_ref:DI ("g_9")
[flags 0x2]  <var_decl 0x7ffff5ae50a0 g_9>) [0 g_9+0 S4 A32])
                    (const_int 1 [0x1]))
                (nil)))))

(insn 7 6 8 2 t.c:10 (parallel [
            (set (reg:QI 68)
                (ior:QI (subreg:QI (reg:SI 59 [ D.2732 ]) 0)
                    (const_int -2 [0xfffffffffffffffe])))
            (clobber (reg:CC 17 flags))
        ]) 398 {*iorqi_1} (expr_list:REG_UNUSED (reg:CC 17 flags)
        (nil)))

(insn 8 7 9 2 t.c:10 (parallel [
            (set (reg:SI 69)
                (zero_extend:SI (reg:QI 68)))
            (clobber (reg:CC 17 flags))
        ]) 119 {*zero_extendqisi2_movzbl_and} (expr_list:REG_DEAD (reg:QI 68)
        (expr_list:REG_UNUSED (reg:CC 17 flags)
            (nil))))

and somewhere forgets to apply the zero-extension:

Successfully matched this instruction:
(set (reg:SI 59 [ D.2732 ])
    (ior:SI (reg:SI 67 [ g_9 ])
        (const_int 1 [0x1])))
Successfully matched this instruction:
(set (reg:SI 69)
    (const_int -1 [0xffffffffffffffff]))


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3/4.4/4.5 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2010-03-19 12:06 -------
Breakpoint 7, combine_simplify_rtx (x=0x7ffff5ae6e58, op0_mode=VOIDmode, 
    in_dest=0) at /space/rguenther/src/svn/trunk/gcc/combine.c:4861
4861      enum rtx_code code = GET_CODE (x);
(set (reg:SI 69)
    (and:SI (subreg:SI (ior:QI (subreg:QI (ior:SI (reg:SI 67 [ g_9 ])
                        (const_int 1 [0x1])) 0)
                (const_int -2 [0xfffffffffffffffe])) 0)
        (const_int 255 [0xff])))
(gdb) finish
Value returned is $19 = (struct rtx_def *) 0x7ffff5ae6e58
(gdb) call debug_rtx ($19)
(set (reg:SI 69)
    (const_int -1 [0xffffffffffffffff]))

but combine_simplify_rtx didn't simplify the subexpressions without the
set.  Hm.


-- 

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|2010-03-19 11:02:13         |2010-03-19 12:06:17
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3/4.4/4.5 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #7 from rguenth at gcc dot gnu dot org  2010-03-19 12:40 -------
make_extraction (mode=SImode, inner=0x7ffff5b48ac8, pos=0, pos_rtx=0x0, len=8, 
    unsignedp=1, in_dest=0, in_compare=0)
    at /space/rguenther/src/svn/trunk/gcc/combine.c:6648
6648      enum machine_mode is_mode = GET_MODE (inner);
(gdb) call debug_rtx (inner)
(subreg:SI (ior:QI (subreg:QI (ior:SI (reg:SI 67 [ g_9 ])
                (const_int 1 [0x1])) 0)
        (const_int -2 [0xfffffffffffffffe])) 0)


      if (CONST_INT_P (new_rtx))
        return gen_int_mode (INTVAL (new_rtx), mode);

misses the nececssary truncation.  Dropping the special casing works
(but doesn't optimize).  Fixing the appearantly many issues works as well.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3/4.4/4.5 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2010-03-20 13:44 -------
Subject: Bug 43438

Author: rguenth
Date: Sat Mar 20 13:44:18 2010
New Revision: 157592

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=157592
Log:
2010-03-20  Richard Guenther  <rguenther@suse.de>

        PR rtl-optimization/43438
        * combine.c (make_extraction): Properly zero-/sign-extend an
        extraction of the low part of a CONST_INT.  Also handle
        CONST_DOUBLE.

        * gcc.c-torture/execute/pr43438.c: New testcase.

Added:
    trunk/gcc/testsuite/gcc.c-torture/execute/pr43438.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/combine.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3/4.4 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #9 from rguenth at gcc dot gnu dot org  2010-03-20 13:44 -------
Fixed for 4.5 sofar.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|4.3.4 4.4.3 4.5.0           |4.3.4 4.4.3
      Known to work|4.1.2                       |4.1.2 4.5.0
            Summary|[4.3/4.4/4.5 Regression]    |[4.3/4.4 Regression]
                   |possible wrong code bug     |possible wrong code bug


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3/4.4 Regression] possible wrong code bug

[jakub at gcc dot gnu dot org]

------- Comment #10 from jakub at gcc dot gnu dot org  2010-03-22 15:06 -------
Subject: Bug 43438

Author: jakub
Date: Mon Mar 22 15:05:46 2010
New Revision: 157634

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=157634
Log:
        Backport from mainline:
        2010-03-20  Richard Guenther  <rguenther@suse.de>

        PR rtl-optimization/43438
        * combine.c (make_extraction): Properly zero-/sign-extend an
        extraction of the low part of a CONST_INT.  Also handle
        CONST_DOUBLE.

        * gcc.c-torture/execute/pr43438.c: New testcase.

Added:
    branches/gcc-4_4-branch/gcc/testsuite/gcc.c-torture/execute/pr43438.c
Modified:
    branches/gcc-4_4-branch/gcc/ChangeLog
    branches/gcc-4_4-branch/gcc/combine.c
    branches/gcc-4_4-branch/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3 Regression] possible wrong code bug

[jakub at gcc dot gnu dot org]

------- Comment #11 from jakub at gcc dot gnu dot org  2010-03-22 15:28 -------
Fixed also on 4.4 branch.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|4.1.2 4.5.0                 |4.1.2 4.5.0 4.4.4
            Summary|[4.3/4.4 Regression]        |[4.3 Regression] possible
                   |possible wrong code bug     |wrong code bug


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2010-04-20 13:09 -------
Fixed.


-- 

rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438

[Bug rtl-optimization/43438] [4.3 Regression] possible wrong code bug

[rguenth at gcc dot gnu dot org]

------- Comment #13 from rguenth at gcc dot gnu dot org  2010-04-20 13:10 -------
Subject: Bug 43438

Author: rguenth
Date: Tue Apr 20 13:09:42 2010
New Revision: 158555

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=158555
Log:
2010-04-20  Richard Guenther  <rguenther@suse.de>

        PR rtl-optimization/43438
        * combine.c (make_extraction): Properly zero-/sign-extend an
        extraction of the low part of a CONST_INT.

        * gcc.c-torture/execute/pr43438.c: New testcase.

Added:
    branches/gcc-4_3-branch/gcc/testsuite/gcc.c-torture/execute/pr43438.c
Modified:
    branches/gcc-4_3-branch/gcc/ChangeLog
    branches/gcc-4_3-branch/gcc/combine.c
    branches/gcc-4_3-branch/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43438