Re: optimization/10877: [3.3/3.4 regression] miscompilation with -O3 -fPIC on x86

[Andrew Pinski <pinskia@physics.uc.edu>]

The following reply was made to PR optimization/10877; it has been noted by GNATS.

From: Andrew Pinski <pinskia@physics.uc.edu>
To: bangerth@dealii.org, gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org,
   lloyd@acm.jhu.edu, nobody@gcc.gnu.org, gcc-gnats@gcc.gnu.org
Cc: Andrew Pinski <pinskia@physics.uc.edu>
Subject: Re: optimization/10877: [3.3/3.4 regression] miscompilation with -O3 -fPIC on x86
Date: Mon, 19 May 2003 21:58:26 -0400

 It does not fail for me though on i686-pc-linux-gnu with GCC: 3.4  
 20030517 (experimental).
 Or on i686-unkown-openbsd3.1 with gcc version 3.4 20030519  
 (experimental).
 
 tin:~/src/gnu/gcc>g++ -O3 -fPIC ../gcctest/testpic.cc
 tin:~/src/gnu/gcc>./a.out
 tin:~/src/gnu/gcc>more ../gcctest/testpic.cc
      int* i;
 
      int& get_x() {
        return *i;
      }
 
      int main() {
        int j;
        i = &j;
        get_x();
      }
 
 Thanks,
 Andrew Pinski
 
 PS here is the asm from a working version:
 
          .file   "testpic.cc"
 .globl i
          .bss
          .align 4
          .type   i, @object
          .size   i, 4
 i:
          .zero   4
          .text
          .align 2
          .p2align 4,,15
 .globl _Z5get_xv
          .type   _Z5get_xv, @function
 _Z5get_xv:
 .LFB4:
          call    __i686.get_pc_thunk.ax
          addl    $_GLOBAL_OFFSET_TABLE_, %eax
          pushl   %ebp
 .LCFI0:
          movl    i@GOT(%eax), %edx
          movl    %esp, %ebp
 .LCFI1:
          popl    %ebp
          movl    (%edx), %eax
          ret
 .LFE4:
          .size   _Z5get_xv, .-_Z5get_xv
          .align 2
          .p2align 4,,15
 .globl main
          .type   main, @function
 main:
 .LFB5:
          pushl   %ebp
 .LCFI2:
          movl    %esp, %ebp
 .LCFI3:
          leal    -8(%ebp), %eax
          pushl   %ebx
 .LCFI4:
          subl    $4, %esp
 .LCFI5:
          andl    $-16, %esp
          call    __i686.get_pc_thunk.bx
          addl    $_GLOBAL_OFFSET_TABLE_, %ebx
          movl    i@GOT(%ebx), %ecx
          movl    %eax, (%ecx)
          call    _Z5get_xv@PLT
          movl    -4(%ebp), %ebx
          xorl    %eax, %eax
          leave
          ret
 .LFE5:
          .size   main, .-main
          .section         
 .gnu.linkonce.t.__i686.get_pc_thunk.ax,"ax",@progbits
 .globl __i686.get_pc_thunk.ax
          .hidden __i686.get_pc_thunk.ax
          .type   __i686.get_pc_thunk.ax, @function
 __i686.get_pc_thunk.ax:
          movl    (%esp), %eax
          ret
          .section         
 .gnu.linkonce.t.__i686.get_pc_thunk.bx,"ax",@progbits
 .globl __i686.get_pc_thunk.bx
          .hidden __i686.get_pc_thunk.bx
          .type   __i686.get_pc_thunk.bx, @function
 __i686.get_pc_thunk.bx:
          movl    (%esp), %ebx
          ret
          .ident  "GCC: (GNU) 3.4 20030517 (experimental)"
 
 
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit- 
 trail&database=gcc&pr=10877