[LLVMdev] Sub registers in inline assembly

[Chris Lattner]

On Mar 1, 2011, at 1:24 PM, Damien Vincent wrote:

> 
>   I was wondering if llvm supports sub registers in an inline asm string.
>   For example, in gcc, using modifiers %w0 makes it possible to access ax if %0 refers to eax.
> 
>   If there is any support, do you know where it is implemented ? I'd like to add such a support for another target.

Hi Damien,

It sure does.  These are considered "modifier" characters and are handled in (e.g.) X86AsmPrinter::PrintAsmOperand.

You can send some C code with asms in it through x86 clang to see what IR it generates or use the llvm demo page.

-Chris