[Bug c/31701] New: Program giving segmentation fault with '-O2' optimization.

[Ashay dot Jaiswal at kpitcummins dot com]

Hello all,

I have successfully built SH4-Linux toolchain based on
(binutils-2.17, gcc-4.2-20061205, glibc-2.5) for Renesas SH target.

I am facing problem while executing the following program.

 ------------------------------------------------------------------
 #include <stdio.h>        
 extern void func();          
 typedef struct abc {       
 char name[16]; 
 }ABC;  
 main()  
 {          
     int i; 
     ABC buffer[20];         
     for (i=0; i<20; i++)                 
         buffer[i].name[0] = 't';         
   if (buffer[10].name[0] == 't')       
   printf("OK\n"); 
   else   
   printf("NOT OK\n");      
}           
-------------------------------------------------------------------------       

The above program when compiled with '-O0' optimization executes successfully,
but I am getting segmentation fault error while executing the program compiled 
with '-O2' optimization.

Observations:

1. I found differences in the assembly output of the program when compiled
   with '-O0' and '-O2' optimization.
   It seems stack register get corrupted with '-O2' optimization.

   Following code corrupts the stack register
   L10:
            mov.w   .L18,r14
            mov.l     .L19,r1
            add       r14,r14
            mov      r14,r15        <<here it is corrupting the stack register
            mov.l     @r15+,r14
            jmp       @r1
            nop
            .align 1

2. Program executes successfully when compiled with '-O2' and
   '-fno-optimize-sibling-calls' options.

3. Same problem is encountered with gcc-4.0.1 and after reverting the
   patch PR21265(http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21265) the program
   executes successfully with '-O2' optimization. But this solution doesn't
work with gcc-4.2-20061205 based toolchain.

Any help on this will be appreciated.

Regards,
Ashay Jaiswal
KPIT Cummins Infosystems Ltd,
Pune (INDIA)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Free download of GNU based SH-Linux toolchains for Renesas' SH Series.          
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Visit http://www.kpitgnutools.com for details.           
Latest versions of KPIT GNU SH-Linux tools were released on April 5, 2007.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


-- 
           Summary: Program giving segmentation fault with '-O2'
                    optimization.
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Ashay dot Jaiswal at kpitcummins dot com
 GCC build triplet: i686-pc-linux
  GCC host triplet: sh4-unknown-linux
GCC target triplet: sh4-unknown-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31701