[Bug c/13488] New: Optimizer bug when casting "long long" to "short" or "char"

[Bug c/13488] New: Optimizer bug when casting "long long" to "short" or "char"

[mhx-perl at gmx dot net]

This bug is present with at least gcc-2.95.3, gcc-3.3.2 and gcc-3.4.

mhx@r2d2 ~ $ uname -a
Linux r2d2.mhxnet.de 2.4.22-gentoo-r2 #2 Sun Dec 21 18:25:49 MET 2003 i686
Intel(R) Pentium(R) III Mobile CPU      1000MHz GenuineIntel GNU/Linux

mhx@r2d2 ~ $ gcc-3.4 -v
Reading specs from
/home/mhx/gcc/gcc-3.4-20031217/lib/gcc/i686-pc-linux-gnu/3.4/specs
Configured with: ./configure --prefix=/home/mhx/gcc/gcc-3.4-20031217
--enable-languages=c --program-suffix=-3.4
Thread model: posix
gcc version 3.4 20031217 (experimental)

mhx@r2d2 ~ $ gcc-3.3.2 -v
Reading specs from /home/mhx/gcc/gcc-3.3.2/lib/gcc-lib/i686-pc-linux-gnu/3.3.2/specs
Configured with: ./configure --prefix=/home/mhx/gcc/gcc-3.3.2
--program-suffix=-3.3.2 --enable-languages=c,c++
Thread model: posix
gcc version 3.3.2

mhx@r2d2 ~ $ gcc-2.95.3 -v
Reading specs from
/home/mhx/gcc/gcc-2.95.3/lib/gcc-lib/i686-pc-linux-gnu/2.95.3/specs
gcc version 2.95.3 20010315 (release)

When casting a "long long" variable to "short" or "char" and storing
the result back to the same "long long" variable, the value that is
being stored is wrong. Casting to "int" or "long" works. Not storing
to the same variable also works. Disabling optimizations (-O0) also
makes it work. When optimizations are enables, it doesn't matter if
-O1, -O2 or -O3 is given.

The code that fails is e.g.:

  long long ll2s_1(long long x)
  {
    x = (short) x;
    return x;
  }

However, this works correctly:

  long long ll2s_2(long long x)
  {
    return (short) x;
  }

I'll try to attach the preprocessed code that causes the failure.
The executable has been generated with:

  gcc-3.4 -save-temps -O1 -o test test.c

The output of the executable on my machine is as follows:

           0          12           0          12           0           0           0
 10000001000          12         -24          12       -6168  1410066408  1410066408
 20000002000          12         -48          12      -12336 -1474834480 -1474834480
 30000003000          12         -72          12      -18504   -64768072   -64768072
 40000004000          12         -96          12      -24672  1345298336  1345298336
 50000005000          12        -120          12      -30840 -1539602552 -1539602552
 60000006000          12         112          12       28528  -129536144  -129536144
 70000007000          12          88          12       22360  1280530264  1280530264
 80000008000          12          64          12       16192 -1604370624 -1604370624
 90000009000          12          40          12       10024  -194304216  -194304216

Obviously, while columns 2/3 and 4/5 should be identical, they aren't.
Disabling optimizations (turning -O1 into -O0) gives the expected result:

           0           0           0           0           0           0           0
 10000001000         -24         -24       -6168       -6168  1410066408  1410066408
 20000002000         -48         -48      -12336      -12336 -1474834480 -1474834480
 30000003000         -72         -72      -18504      -18504   -64768072   -64768072
 40000004000         -96         -96      -24672      -24672  1345298336  1345298336
 50000005000        -120        -120      -30840      -30840 -1539602552 -1539602552
 60000006000         112         112       28528       28528  -129536144  -129536144
 70000007000          88          88       22360       22360  1280530264  1280530264
 80000008000          64          64       16192       16192 -1604370624 -1604370624
 90000009000          40          40       10024       10024  -194304216  -194304216

Here's the source code (just in case attaching won't work, this is
my first bug report here...):

----8<-------------------------------------------------------------------

#include <stdio.h>

long long ll2c_1(long long x)
{
  x = (signed char) x;
  return x;
}

long long ll2c_2(long long x)
{
  return (signed char) x;
}

long long ll2s_1(long long x)
{
  x = (short) x;
  return x;
}

long long ll2s_2(long long x)
{
  return (short) x;
}

long long ll2i_1(long long x)
{
  x = (int) x;
  return x;
}

long long ll2i_2(long long x)
{
  return (int) x;
}

int main(void)
{
  long long a;
  for (a = 0LL; a < 100000000000LL; a += 10000001000LL)
  {
    printf("%12lld", a);
    printf("%12lld", ll2c_1(a));
    printf("%12lld", ll2c_2(a));
    printf("%12lld", ll2s_1(a));
    printf("%12lld", ll2s_2(a));
    printf("%12lld", ll2i_1(a));
    printf("%12lld", ll2i_2(a));
    printf("\n");
  }
  return 0;
}

-- 
           Summary: Optimizer bug when casting "long long" to "short" or
                    "char"
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mhx-perl at gmx dot net
                CC: gcc-bugs at gcc dot gnu dot org
 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=13488

[Bug c/13488] Optimizer bug when casting "long long" to "short" or "char"

[mhx-perl at gmx dot net]

------- Additional Comments From mhx-perl at gmx dot net  2003-12-25 12:05 -------
Created an attachment (id=5369)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=5369&action=view)
Preprocessed source of code that causes the failure


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488

[Bug c/13488] Optimizer bug when casting "long long" to "short" or "char"

[mhx-perl at gmx dot net]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mhx-perl at gmx dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488

[Bug c/13488] Optimizer bug when casting "long long" to "short" or "char"

[mhx-perl at gmx dot net]

------- Additional Comments From mhx-perl at gmx dot net  2003-12-25 13:00 -------
FYI, I can also confirm the bug for a cygwin gcc-3.2 on the same machine.

$ uname -a
CYGWIN_NT-5.0 R2D2 1.5.3(0.90/3/2) 2003-09-01 13:15 i686 unknown unknown Cygwin

$ gcc -v
Reading specs from /usr/lib/gcc-lib/i686-pc-cygwin/3.2/specs
Configured with: /netrel/src/gcc-3.2-3/configure --enable-languages=c,c++,f77,ja
va --enable-libgcj --enable-threads=posix --with-system-zlib --enable-nls --with
out-included-gettext --enable-interpreter --disable-sjlj-exceptions --disable-ve
rsion-specific-runtime-libs --enable-shared --build=i686-pc-linux --host=i686-pc
-cygwin --target=i686-pc-cygwin --enable-haifa --prefix=/usr --exec-prefix=/usr
--sysconfdir=/etc --libdir=/usr/lib --includedir=/nonexistent/include --libexecd
ir=/usr/sbin
Thread model: posix
gcc version 3.2 20020927 (prerelease)

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488

[Bug optimization/13488] Optimizer bug when casting "long long" to "short" or "char"

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 15:52 -------
I can confirm this and this is not a regression, even 2.91.6 causes this.
Life analysis causes this problem, it removes the load from 4(%esp) which is the argument.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|c                           |optimization
     Ever Confirmed|                            |1
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2003-12-25 15:52:55
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488

[Bug optimization/13488] [3.4 only] Optimizer bug when casting "long long" to "short" or "char"

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-04-01 13:51 -------
This is fixed in 3.5.0 (20040331) but it was not fixed for 3.4.0 (20040116) and I do not 
have a newer 3.4.0 to say if it was fixed there too.  Could someone check?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |3.5.0
            Summary|Optimizer bug when casting  |[3.4 only] Optimizer bug
                   |"long long" to "short" or   |when casting "long long" to
                   |"char"                      |"short" or "char"
   Target Milestone|---                         |3.4.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488

[Bug optimization/13488] [3.4 only] Optimizer bug when casting "long long" to "short" or "char"

[jakub at gcc dot gnu dot org]

------- Additional Comments From jakub at gcc dot gnu dot org  2004-04-02 12:18 -------


*** This bug has been marked as a duplicate of 14235 ***

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488

[Bug optimization/13488] [3.4 only] Optimizer bug when casting "long long" to "short" or "char"

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-04-13 20:36 -------
Subject: Bug 13488

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_3-rhl-branch
Changes by:	jakub@gcc.gnu.org	2004-04-13 20:36:16

Modified files:
	gcc            : ChangeLog expr.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.c-torture/compile: 20040304-1.c 
	gcc/testsuite/gcc.c-torture/execute: 20040402-1.c 

Log message:
	2004-03-04  Eric Botcazou  <ebotcazou@libertysurf.fr>
	
	PR optimization/14235
	* expr.c (convert_move): Copy the source to a new pseudo
	when converting from a sub-word source to a larger-than-word
	register which conflicts with the source.
	
	* gcc.c-torture/compile/20040304-1.c: New test.
	
	2004-04-02  Jakub Jelinek  <jakub@redhat.com>
	
	PR optimization/13488
	* gcc/testsuite/gcc.c-torture/execute/20040402-1.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-rhl-branch&r1=1.16114.2.523.2.104&r2=1.16114.2.523.2.105
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/expr.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-rhl-branch&r1=1.498.2.17.2.16&r2=1.498.2.17.2.17
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-rhl-branch&r1=1.2261.2.170.2.55&r2=1.2261.2.170.2.56
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.c-torture/compile/20040304-1.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-rhl-branch&r1=NONE&r2=1.1.20.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.c-torture/execute/20040402-1.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-rhl-branch&r1=NONE&r2=1.1.2.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488

[Bug optimization/13488] [3.4 only] Optimizer bug when casting "long long" to "short" or "char"

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-04-22 17:50 -------
Subject: Bug 13488

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-rhl-branch
Changes by:	jakub@gcc.gnu.org	2004-04-22 17:50:29

Modified files:
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.c-torture/execute: 20040402-1.c 

Log message:
	PR optimization/13488
	* gcc/testsuite/gcc.c-torture/execute/20040402-1.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-rhl-branch&r1=1.3389.2.170.2.2&r2=1.3389.2.170.2.3
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.c-torture/execute/20040402-1.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-rhl-branch&r1=NONE&r2=1.1.4.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13488