Forwarding to the list because I sent it to the wrong list address the first time. D'oh!
-------- Forwarded Message -------- From: Ian Romanick <[email protected]> To: Brian Paul <[email protected]> Cc: [email protected] Subject: Re: Mesa (master): i965: implement GL_EXT_texture_swizzle Date: Wed, 28 Jan 2009 16:13:53 -0800 On Wed, 2009-01-28 at 14:07 -0800, Brian Paul wrote: > Module: Mesa > Branch: master > Commit: c0d3b7679aa90e1a0dca2db152205efaec088b90 > URL: > http://cgit.freedesktop.org/mesa/mesa/commit/?id=c0d3b7679aa90e1a0dca2db152205efaec088b90 > > Author: Brian Paul <[email protected]> > Date: Wed Jan 28 14:50:03 2009 -0700 > > i965: implement GL_EXT_texture_swizzle > > If the texture swizzle is not XYZW (no-op) add an extra MOV instruction > after the TEX instruction to rearrange the components. Is this a good idea? It doesn't seem like we're doing app developers a service by inserting hidden instructions or by forcing a re-compile when API state changes. If this extension can't be implemented "for free" in the texture sampler, I'm not convinced that it should be exposed. It's a good extension, and there is hardware that can implement it directly in the texture samplers. However, i965 is not that hardware. To be honest, I feel the same way about the extra code inserted for MESA_FORMAT_YCBCR textures. We ought to have a trimmed-down GL_EXT_422_pixels to expose the functionality of the sampler, and we should require the app do the color-space conversion. My primary concern in both cases is not the extra instruction added. My concern is the hidden, unpredictable (by the app) re-compile. I think we can make this better with some different back-end infrastructure, but we'll need to write that code first. Basically, we need to implement "relocs" / back-patching in the loader.
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