Re: Inline asm constraint help

[Jason Thorpe <thorpej%me.com@localhost>]

No, I mean wN (32-bit) vs xN (64-bit) names of the general purpose registers.  Specifically, I want to use ldxr and stxr to operate on “int *” memory locations.  I know the syntax, just can’t get GCC to emit it :-/

(Sorry, I just don’t have the GCC source handy right now... and it’s online docs don’t even mention the “x” modifier as far as I can tell, but I observed its behavior.)

-- thorpej
Sent from my iPhone.

> On Jan 31, 2019, at 7:08 AM, Martin Husemann <martin%duskware.de@localhost> wrote:
> 
>> On Thu, Jan 31, 2019 at 02:01:08AM +0200, Jason Thorpe wrote:
>> Trying to fix a package on aarch64 and it needs some inline asm.  My problem: I can?t figure out the constraint modifier to force wN instead of xN for register operands.  The Internet Oracle has apparently deemed me unworthy of this knowledge.
> 
> Using the source it looks like:
> 
> (define_register_constraint "w" "FP_REGS"
>  "Floating point and SIMD vector registers.")
> 
> or
> 
> (define_register_constraint "x" "FP_LO_REGS"
>  "Floating point and SIMD vector registers V0 - V15.")
> 
> Is that what you mean?
> 
> Martin