From 6ee500cfd28324bef27f145fbe03e77993810c45 Mon Sep 17 00:00:00 2001 From: Paul Berry Date: Thu, 13 Dec 2012 12:45:37 -0800 Subject: [PATCH] mesa: Add an option so driver can opt out of varying packing. MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit On hardware that supports a limited number of texture indirections, varying packing will comsume an extra texture indirection, since ALU operations are needed in the fragment shader to unpack the varyings before any texturing can be done. This patch introduces a new driver option, ctx->Const.DisableVaryingPacking, which can be used by a driver to opt out of varying packing if the extra texture indirection is costly enough to outweigh the advantages of packing varyings. Reviewed-by: Marek Olšák --- src/mesa/main/mtypes.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h index 11a8322..b59498f 100644 --- a/src/mesa/main/mtypes.h +++ b/src/mesa/main/mtypes.h @@ -2928,6 +2928,17 @@ struct gl_constants /** GL_ARB_map_buffer_alignment */ GLuint MinMapBufferAlignment; + + /** + * Disable varying packing. This is out of spec, but potentially useful + * for older platforms that supports a limited number of texture + * indirections--on these platforms, unpacking the varyings in the fragment + * shader increases the number of texture indirections by 1, which might + * make some shaders not executable at all. + * + * Drivers that support transform feedback must set this value to GL_FALSE. + */ + GLboolean DisableVaryingPacking; }; -- 2.7.4