Another OpenGL 4.2 Extension Comes Close For Intel Mesa
Written by Michael Larabel in Intel on 28 April 2015 at 10:01 PM EDT. 13 Comments
Another OpenGL 4 extension is nearing completion within the open-source Mesa software library. The extension t his time is ARB_shader_image_load_store, which is needed for OpenGL 4.2 compliance.

The GL_ARB_shader_image_load_store has been a work-in-progress for a while by Francisco Jerez. On Tuesday he published what he referred to as "the last major piece missing in the i965 driver for ARB_shader_image_load_store support. It has been tested on [Ivy Bridge], [Haswell] and [Broadwell] and passes all applicable piglit tests (some 4400 currently) modulo hardware bugs."

The patch series implements the ARB_shader_image_load_store built-ins for the Intel (i965) DRI driver. This latest patch series consists of twenty-three patches (and almost 2K lines of new code) and for now can be found on the Mesa-dev mailing list.

Per the registry, "this extension provides GLSL built-in functions allowing shaders to load from, store to, and perform atomic read-modify-write operations to a single level of a texture object from any shader stage. These built-in functions are named imageLoad(), imageStore(), and imageAtomic*(), respectively, and accept integer texel coordinates to identify the texel accessed. The extension adds the notion of "image units" to the OpenGL API, to which texture levels are bound for access by the GLSL built-in functions."

Of course, before the Intel Linux driver can officially advertise OpenGL 4.2 support, it must finish the few remaining OpenGL 4.0 and 4.1 extensions, which we'll hopefully see done in the months ahead... Stay tuned to hear about more Mesa developments on Phoronix.
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