[Bug c/13028] New: ia64 gcc with -O2 does not store value in register into local varible

[Bug c/13028] New: ia64 gcc with -O2 does not store value in register into local varible

[czang at panasas dot com]

This can be demonstrated with the following sample program:

/*
 * program starts
 */

#define ntoh64(_src_, _dest_) { \
  unsigned int *src_p = (unsigned int *) _src_;   \
  unsigned int *dest_p = (unsigned int *) _dest_; \
    *dest_p++ = *src_p++; \
    *dest_p++ = *src_p++; \
}

void
call(unsigned long *number_p)
{
  unsigned long seqno;

  ntoh64(number_p, &seqno);

  printf("in reply_received: seqno is %lu\n", seqno);

  printf("in reply_received: seqno is %lu\n", seqno);
}

main() {
  unsigned long number = 1010101;
  call(&number);
}

/*
 * program ends
 */

The following is the compile command line:

[build-hp1] gcc -v -save-temps -O2 compiler.c 
Reading specs from /usr/lib/gcc-lib/ia64-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-112.7.2)
 /usr/lib/gcc-lib/ia64-redhat-linux/2.96/cpp0 -lang-c -v -D__GNUC__=2
-D__GNUC_MINOR__=96 -D__GNUC_PATCHLEVEL__=0 -D__ia64 -D__ia64__ -D__linux
-D__linux__ -D_LONGLONG -Dlinux -Dunix -D__LP64__ -D__ELF__ -D__ia64 -D__ia64__
-D__linux -D__linux__ -D_LONGLONG -D__linux__ -D__unix__ -D__LP64__ -D__ELF__
-D__linux -D__unix -Asystem(linux) -Acpu(ia64) -Amachine(ia64) -D__OPTIMIZE__
-D__LONG_MAX__=9223372036854775807L compiler.c compiler.i
GNU CPP version 2.96 20000731 (Red Hat Linux 7.2 2.96-112.7.2) (cpplib) (IA-64)
ignoring nonexistent directory "/usr/ia64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc-lib/ia64-redhat-linux/2.96/include
 /usr/include
End of search list.
 /usr/lib/gcc-lib/ia64-redhat-linux/2.96/cc1 compiler.i -mb-step -quiet
-dumpbase compiler.c -O2 -version -o compiler.s
GNU C version 2.96 20000731 (Red Hat Linux 7.2 2.96-112.7.2) (ia64-redhat-linux)
compiled by GNU C version 2.96 20000731 (Red Hat Linux 7.2 2.96-112.7.2).
 as -x -o compiler.o compiler.s
 /usr/lib/gcc-lib/ia64-redhat-linux/2.96/collect2 -dynamic-linker
/lib/ld-linux-ia64.so.2 /usr/lib/gcc-lib/ia64-redhat-linux/2.96/../../../crt1.o
/usr/lib/gcc-lib/ia64-redhat-linux/2.96/../../../crti.o
/usr/lib/gcc-lib/ia64-redhat-linux/2.96/crtbegin.o
-L/usr/lib/gcc-lib/ia64-redhat-linux/2.96
-L/usr/lib/gcc-lib/ia64-redhat-linux/2.96/../../.. compiler.o -lgcc -lc -lgcc
/usr/lib/gcc-lib/ia64-redhat-linux/2.96/crtend.o
/usr/lib/gcc-lib/ia64-redhat-linux/2.96/../../../crtn.o

The following is the run of the generated program:

[build-hp1] a.out
in reply_received: seqno is 0
in reply_received: seqno is 1010101

-- 
           Summary: ia64 gcc with -O2 does not store value in register into
                    local varible
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: czang at panasas dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-11-12 22:02 -------
Not a bug as the types unsigned int and unsigned long are know not to alias (really their pointers 
are) each other.  Also you are using an old version of gcc (2.96 a non-supported one at that), try to 
update it.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[czang at panasas dot com]

------- Additional Comments From czang at panasas dot com  2003-11-14 15:18 -------
It's debatable whether this is a bug but this is certainly a limitation.  Is
this documented anywhere?

By the way I hope you at least try the sample program with your newer version of
gcc to see if it's fixed.  That should only take you minutes.  To download and
compile the compiler would take me at least hours.  Thanks.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[schwab at suse dot de]

------- Additional Comments From schwab at suse dot de  2003-11-14 15:29 -------
Look up -Wstrict-aliasing in the manual. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[dhazeghi at yahoo dot com]

------- Additional Comments From dhazeghi at yahoo dot com  2003-12-09 23:10 -------
As pointed out, you're violating strict aliasing rules. With gcc 3.3:

bash-2.05a$ gcc -Wall -O3  bug.c 
bug.c: In function `call':
bug.c:17: warning: dereferencing type-punned pointer will break strict-aliasing rules

If you want this to work, you'll have to compile with -fno-strict-aliasing, in which case it does 
work, at least with 3.3.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[czang at panasas dot com]

------- Additional Comments From czang at panasas dot com  2003-12-10 12:02 -------
thanks for the info.  I'll close this bug and we'll upgrade our gcc when it's 
the right time.  Our engineers are warned about the risk aliasing types of 
different sizes when using optimization.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[dhazeghi at yahoo dot com]

------- Additional Comments From dhazeghi at yahoo dot com  2003-12-10 17:58 -------
mark as "resolved invalid" (bugzilla consistency reasons).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[dhazeghi at yahoo dot com]

------- Additional Comments From dhazeghi at yahoo dot com  2003-12-10 17:58 -------
Please don't mark bugs as closed...

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|CLOSED                      |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-06-05 08:32 -------
Reopening to ...

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028

[Bug c/13028] ia64 gcc with -O2 does not store value in register into local varible

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-06-05 08:32 -------
Mark as a dup of bug 21920.

*** This bug has been marked as a duplicate of 21920 ***

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13028