[Bug c/11304] New: Wrong code production with -fomit-frame-pointer

["manuel dot serrano at sophia dot inria dot fr" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11304

           Summary: Wrong code production with -fomit-frame-pointer
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: manuel dot serrano at sophia dot inria dot fr
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: Linux owens.inria.fr 2.4.21
GCC target triplet: i386

I have found a problem with GCC3.2 and GCC3.3 when -fomit-frame-pointer
and -O2 are both used. The bug seems to be concerning the registers allocation 
that seems erroneous. The problem does not exist with GCC2.95. It goes away
if either -fomit-frame-pointer or -O2 are disabled.


*** Operating system:
=====================
$ uname -a 
Linux owens.inria.fr 2.4.21 #1 Tue Jun 17 16:26:21 CEST 2003 i686 GNU/Linux

*** GCC version:
================
gcc -v
Reading specs from /usr/lib/gcc-lib/i386-linux/3.3/specs
Configured with: ../src/configure -v
--enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr
--mandir=/usr/share/man --infodir=/usr/share/info
--with-gxx-include-dir=/usr/include/c++/3.3 --enable-shared --with-system-zlib
--enable-nls --without-included-gettext --enable-__cxa_atexit
--enable-clocale=gnu --enable-debug --enable-java-gc=boehm
--enable-java-awt=xlib --enable-objc-gc i386-linux
Thread model: posix
gcc version 3.3 (Debian)

*** Source code:
================
int hux(int x){
   if(x){
      foo( 4 );
      return x;
   }
   failure_then_exit(x);
}

*** GCC Command line:
=====================

gcc -O2 -fomit-frame-pointer foo.c

*** Preprocessed source file:
=============================
$ gcc -fomit-frame-pointer foo.c -S -O2 -save-temps
$ cat foo.i 
# 1 "foo.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "foo.c"
int hux(int x)
{
   if(x)
   {
      foo( 4 );
      return x;
   }
   failure_then_exit(x);
}


*** Assembly file (that I known you don't want bug that shows the bug):
=======================================================================
$ cat foo.s 
        .file   "foo.c"
        .text
        .p2align 2,,3
.globl hux
        .type   hux, @function
hux:
        pushl   %ebx
        subl    $8, %esp
        movl    16(%esp), %ebx
        testl   %ebx, %ebx
        je      .L2
        subl    $12, %esp
        pushl   $4
        call    foo                    # <-- HERE, THE REGISTER EAX IS NOT
.L3:                                   # RELOADED !!!
        addl    $24, %esp
        popl    %ebx
        ret
        .p2align 2,,3
.L2:
        subl    $12, %esp
        pushl   $0
        call    failure_then_exit
        jmp     .L3
        .size   hux, .-hux
        .ident  "GCC: (GNU) 3.3 (Debian)"