llvm dev - Jul 2010 - [LLVMdev] warnings in inline assembly with used labels and -Wunused-label

Hi,

llvm-gcc 4.2 generates warnings when I compile inline assembly code that
contains used labels with -Wunused-label. The generated code seems to work yet.
gcc 4.2 doesn't generate those warnings. I haven't found any bugs
regarding this issue in the llvm bug database.

Does anyone know if this is a known llvm issue? Is it a warning that I can
ignore and does not affect the generated code? Is there a workaround to avoid
these warnings (without turning off -Wunused-label)?


Here is a small sample code that exhibits the issue:

int main()
{
__asm__
	{
MyLabel:
		sub	ebx,8
		jg MyLabel
	}
	
	return 0;
}


Compile with llvm-gcc 4.2 on MacOSX 10.6:

llvm-gcc-4.2 -arch i386 -Wunused-label -fasm-blocks -o inlineassembly_llvm
inlineassembly.c
inlineassembly.c: In function ‘main’:
inlineassembly.c:7: warning: label ‘LASM$MyLabel’ defined but not used

Compile with gcc 4.2 on MacOSX 10.6:

gcc -arch i386 -Wunused-label -fasm-blocks -o inlineassembly inlineassembly.c
no warnings


Thanks,
Alexandre

On Jul 23, 2010, at 2:20 AM, Alexandre Colucci wrote:
> Hi,
> 
> llvm-gcc 4.2 generates warnings when I compile inline assembly code that
contains used labels with -Wunused-label. The generated code seems to work yet.
gcc 4.2 doesn't generate those warnings. I haven't found any bugs
regarding this issue in the llvm bug database.
> 
> Does anyone know if this is a known llvm issue? Is it a warning that I can
ignore and does not affect the generated code? Is there a workaround to avoid
these warnings (without turning off -Wunused-label)?
What version of llvm-gcc 4.2 are you using?  I think that Dale just fixed this
issue, so you might try SVN head to see if it is gone now.

-Chris
> 
> 
> Here is a small sample code that exhibits the issue:
> 
> int main()
> {
> __asm__
> 	{
> MyLabel:
> 		sub	ebx,8
> 		jg MyLabel
> 	}
> 	
> 	return 0;
> }
> 
> 
> Compile with llvm-gcc 4.2 on MacOSX 10.6:
> 
> llvm-gcc-4.2 -arch i386 -Wunused-label -fasm-blocks -o inlineassembly_llvm
inlineassembly.c
> inlineassembly.c: In function ‘main’:
> inlineassembly.c:7: warning: label ‘LASM$MyLabel’ defined but not used
> 
> Compile with gcc 4.2 on MacOSX 10.6:
> 
> gcc -arch i386 -Wunused-label -fasm-blocks -o inlineassembly
inlineassembly.c
> no warnings
> 
> 
> Thanks,
> Alexandre
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

This is fixed in TOT  (rev 107051 for C, 108732 for C++)

On Jul 23, 2010, at 2:20 AMPDT, Alexandre Colucci wrote:
> Hi,
>
> llvm-gcc 4.2 generates warnings when I compile inline assembly code  
> that contains used labels with -Wunused-label. The generated code  
> seems to work yet. gcc 4.2 doesn't generate those warnings. I  
> haven't found any bugs regarding this issue in the llvm bug database.
>
> Does anyone know if this is a known llvm issue? Is it a warning that  
> I can ignore and does not affect the generated code? Is there a  
> workaround to avoid these warnings (without turning off -Wunused- 
> label)?
>
>
> Here is a small sample code that exhibits the issue:
>
> int main()
> {
> __asm__
> 	{
> MyLabel:
> 		sub	ebx,8
> 		jg MyLabel
> 	}
> 	
> 	return 0;
> }
>
>
> Compile with llvm-gcc 4.2 on MacOSX 10.6:
>
> llvm-gcc-4.2 -arch i386 -Wunused-label -fasm-blocks -o  
> inlineassembly_llvm inlineassembly.c
> inlineassembly.c: In function ‘main’:
> inlineassembly.c:7: warning: label ‘LASM$MyLabel’ defined but not used
>
> Compile with gcc 4.2 on MacOSX 10.6:
>
> gcc -arch i386 -Wunused-label -fasm-blocks -o inlineassembly  
> inlineassembly.c
> no warnings
>
>
> Thanks,
> Alexandre
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Thanks a lot. I should have tried ToT.

Alexandre

> This is fixed in TOT  (rev 107051 for C, 108732 for C++)
> 
> On Jul 23, 2010, at 2:20 AMPDT, Alexandre Colucci wrote:
> 
>> Hi,
>> 
>> llvm-gcc 4.2 generates warnings when I compile inline assembly code
that contains used labels with -Wunused-label. The generated code seems to work
yet. gcc 4.2 doesn't generate those warnings. I haven't found any bugs
regarding this issue in the llvm bug database.
>> 
>> Does anyone know if this is a known llvm issue? Is it a warning that I
can ignore and does not affect the generated code? Is there a workaround to
avoid these warnings (without turning off -Wunused-label)?
>> 
>> 
>> Here is a small sample code that exhibits the issue:
>> 
>> int main()
>> {
>> __asm__
>> 	{
>> MyLabel:
>> 		sub	ebx,8
>> 		jg MyLabel
>> 	}
>> 	
>> 	return 0;
>> }
>> 
>> 
>> Compile with llvm-gcc 4.2 on MacOSX 10.6:
>> 
>> llvm-gcc-4.2 -arch i386 -Wunused-label -fasm-blocks -o
inlineassembly_llvm inlineassembly.c
>> inlineassembly.c: In function ‘main’:
>> inlineassembly.c:7: warning: label ‘LASM$MyLabel’ defined but not used
>> 
>> Compile with gcc 4.2 on MacOSX 10.6:
>> 
>> gcc -arch i386 -Wunused-label -fasm-blocks -o inlineassembly
inlineassembly.c
>> no warnings
>> 
>> 
>> Thanks,
>> Alexandre
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
>