Mesa's OpenGL KHR_no_error Support Is Now "Done"

Mesa's support for the OpenGL KHR_no_error extension is now treated as "done" for all drivers.

Intel's Kenneth Graunke landed the commit earlier this evening, "Drivers have supported KHR_no_error for a while. We'd been leaving it marked as "in progress" because there's a zillion places that could get slightly more optimized. But, Timothy and Samuel have already done piles of work, and I think we have a solid implementation at this point. Let's check it off the list."

Indeed, there's been a ton of KHR_no_error work in Mesa with various optimizations to reduce the CPU overhead by disabling various validation/error handling code paths. This can be forced via the MESA_NO_ERROR=1 environment variable for easy testing; but using KHR_no_error with an otherwise buggy OpenGL game/application can lead to undefined behavior when this error checking is disabled.

KHR_no_error was the only extension besides the SPIR-V work (ARB_gl_spirv and ARB_spirv_extensions) needed by the Intel i965 and RadeonSI drivers before clearing OpenGL 4.6 compliance. The SPIR-V ingestion work for OpenGL 4.6 is a big ticket item still requiring more work ahead, but hopefully we'll see GL 4.6 for Mesa 18.0.