[Bug c/37493] New: Auto inline when optimisation is enabled, causes problem.

[prafullat at kpitcummins dot com]

Hi,     
While using GCC 4.3.1, I observed that the specialized inline   
code is generated automatically which causes problem in the following   
case.   
---------------------------------------------------------------------   
/*  File name: t.c   */ 
static int      
WaitLoop (unsigned int count)   
{
asm (" _loop: tst       %0, %0  \n" "bf/s _loop \n" "add #-1, %0": "=r"
(count):"0" (count));   
return count;   
}       

int     
main () 
{       
  volatile int a = WaitLoop (100);      
  a = WaitLoop (200);   
  return 0;     
}       
---------------------------------------------------------------------   
When I compiled this test case using GCC 4.3.1, using following         
command line:   
#sh-elf-gcc -O2 t.c -c  

I got the following error:      

/tmp/cczqWWXN.s: Assembler messages:    
/tmp/cczqWWXN.s:25: Error: symbol '_loop' is already defined            

Note: This error was observed only when "-O2" and "-O3" are used        
as optimization options. There is no error for "-O0" and "-O1"  
options.        

For further investigation, I generated an assembly file.        
It seems that, the function "WaitLoop" is getting in-lined. As the      
"WaitLoop" function is called twice from the "main", it was in-lined     
twice by the compiler.  

Below is the assembly file generated from "t.c".        
---------------------------------------------------------------------   
        .file   "t.c"   
        .text
        .little
        .text
        .align 1
        .align 2
        .global _main
        .type   _main, @function
_main:
        mov.l   r14,@-r15
        mov     #0,r0
        add     #-4,r15
        mov     r15,r14
        mov     r14,r2
        add     #-60,r2
        mov     #100,r1
        add     #4,r14
! 4 "t.c" 1
                _loop:  tst     r1, r1  
                bf/s    _loop   
                add     #-1, r1 
! 0 "" 2
        mov.l   r1,@(60,r2)
        mov.w   .L3,r1
! 4 "t.c" 1
                _loop:  tst     r1, r1  
                bf/s    _loop   
                add     #-1, r1 
! 0 "" 2
        mov.l   r1,@(60,r2)
        mov     r14,r15
        rts     
        mov.l   @r15+,r14
        .align 1
.L3:
---------------------------------------------------------------------   
As a workaround for the above issue, one can use either of the following:       
1.  "-fno-inline" switch used during compilation. OR    
2. Used "noinline" attribute to the "WaitLoop" function.        

Thanks and Regards,     
Prafulla


-- 
           Summary: Auto inline when optimisation is enabled, causes
                    problem.
           Product: gcc
           Version: 4.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: prafullat at kpitcummins dot com
 GCC build triplet: i686-pc-linux
  GCC host triplet: i686-pc-linux
GCC target triplet: sh*-unknown-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37493