On 30.12.2010, at 23:59, Rafael Espindola wrote:
> Author: rafael
> Date: Thu Dec 30 16:59:32 2010
> New Revision: 122643
>
> URL: http://llvm.org/viewvc/llvm-project?rev=122643&view=rev
> Log:
> Add support for declaring register contraints in variables. They are only used
> in asm statements:
>
> register int foo asm("rdi");
>
> asm("..." : ... "r" (foo) ...
>
> We also only accept these variables if the constraint in the asm statement is
> "r".
>
> This fixes most of PR3933.
I'm not very happy with this fix. Using such a pinned variable with inline asm
looks like an edge case.
Most code (e.g. ruby 1.9) uses this as a (premature) optimization so it
shouldn't hurt there but on the other hand
the linux kernel uses this extension to access the stack pointer like a
variable.
register unsigned long current_stack_pointer asm("esp");
foo = current_stack_pointer;
We used to error out on this, now we treat it like normal stack variable and
miscompile the code.
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