[Bug optimization/12404] New: pointer to union member problem

[Bug optimization/12404] New: pointer to union member problem

[yamt at mwd dot biglobe dot ne dot jp]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12404

           Summary: pointer to union member problem
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: yamt at mwd dot biglobe dot ne dot jp
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-unknown-netbsdelf1.6W
  GCC host triplet: i386--netbsdelf
GCC target triplet: i386--netbsdelf

compiling the following program with -O2 for i386
yields the latter asm output.

% gcc -v
Using built-in specs.
Configured with: /usr/src/tools/gcc/../../gnu/dist/gcc/configure --enable-long-long --disable-multilib --enable-threads --build=i386-unknown-netbsdelf --host=i386--netbsdelf --target=i386--netbsdelf : (reconfigured) /usr/src/tools/gcc/../../gnu/dist/gcc/configure --enable-long-long --disable-multilib --enable-threads --build=i386-unknown-netbsdelf1.6W --host=i386--netbsdelf --target=i386--netbsdelf
Thread model: posix
gcc version 3.3.1

============================================================
#include <stdio.h>

int
main()
{
	union { int i; short s; } u[] = {{1}, {2}, {3}};

	printf("%d\n", *&u->s);
}
============================================================
	.file	"a.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"%d\n"
	.text
	.p2align 2,,3
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	subl	$24, %esp
	andl	$-16, %esp
	subl	$8, %esp
	movswl	-24(%ebp),%eax	# <= used before initialized.
	pushl	%eax
	pushl	$.LC0
	movl	$1, -24(%ebp)	# <= initialize here
	movl	$2, -20(%ebp)
	movl	$3, -16(%ebp)
	call	printf
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 3.3.1"

[Bug optimization/12404] pointer to union member problem (aliasing problem)

[pinskia at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12404


pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2003-09-25 21:21:14
               date|                            |
            Summary|pointer to union member     |pointer to union member
                   |problem                     |problem (aliasing problem)


------- Additional Comments From pinskia at gcc dot gnu dot org  2003-09-25 21:21 -------
I can confirm this on the mainline (20030925), the problem is aliasing issue.

[Bug optimization/12404] pointer to union member problem (aliasing problem)

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 03:13 -------
Fixed on the mainline (20031224).

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |3.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12404