Re: [Mesa3d-dev] GSOC: Gallium R300 driver

[Corbin S. <mos...@gm...>]

On Tue, Mar 30, 2010 at 10:05 AM, Luca Barbieri <luc...@gm...> wrote:
> DDX/DDY could cause miscompilation, but I think that only happens if
> LLVM clones or causes some paths to net execute them.
>
> Someone proposed some time ago on llvmdev to add a flag to tell llvm
> to never duplicate an intrinsic, not sure if that went through (iirc,
> it was for a barrier instruction that relied on the instruction
> pointer).
> Alternatively, it should be possible to just disable any passes that
> clone basic blocks if those instructions are present.
>
> The non-execution problem should be fixable by declaring DDX/DDY to
> have global-write-like side effects (this will prevent dead code
> elimination of them if they are totally unused, but hopefully shaders
> are not written so badly they need that).

We're talking about a HW-specific issue here, not anything that needs
global changes. I'm really not sure where you're going with this.

-- 
When the facts change, I change my mind. What do you do, sir? ~ Keynes

Corbin Simpson
<Mos...@gm...>